polymers

Review ReviewPoly(phenylene ether) Based Amphiphilic Poly(phenyleneBlock Copolymers ether) Based Amphiphilic Block Copolymers Edward N. Peters

EdwardSABIC, Selkirk, N. Peters NY 12158, USA; ed.peters@sabic.com; Tel.: +1-518-475-5458 SABIC, Selkirk, NY 12158, USA; [email protected]; Tel.: +1-518-475-5458 Received: 14 August 2017; Accepted: 5 September 2017; Published: 8 September 2017 Received: 14 August 2017; Accepted: 5 September 2017; Published: 8 September 2017 Abstract: Polyphenylene ether (PPE) telechelic macromonomers are unique hydrophobic polyols Abstract: Polyphenylene ether (PPE) telechelic macromonomers are unique hydrophobic polyols which have been used to prepare amphiphilic block copolymers. Various polymer compositions which have been used to prepare amphiphilic block copolymers. Various polymer compositions have have been synthesized with hydrophilic blocks. Their macromolecular nature affords a range of been synthesized with hydrophilic blocks. Their macromolecular nature affords a range of structures structures including random, alternating, and di- and triblock copolymers. New macromolecular including random, alternating, and di- and triblock copolymers. New macromolecular architectures architectures can offer tailored property profiles for optimum performance. Besides reducing can offer tailored property profiles for optimum performance. Besides reducing moisture uptake and moisture uptake and making the polymer surface more hydrophobic, the PPE hydrophobic segment making the polymer surface more hydrophobic, the PPE hydrophobic segment has good compatibility has good compatibility with polystyrene (polystyrene-philic). In general, the PPE contributes to the with polystyrene (polystyrene-philic). In general, the PPE contributes to the toughness, strength, toughness, strength, and thermal performance. Hydrophilic segments go beyond their affinity for and thermal performance. Hydrophilic segments go beyond their affinity for water. Improvements water. Improvements in the interfacial adhesion between polymers and polar substrates via in the interfacial adhesion between polymers and polar substrates via hydrogen bonding and good hydrogen bonding and good compatibility with polyesters (polyester-philic) have been exhibited. compatibility with polyesters (polyester-philic) have been exhibited. The heterogeneity of domains in The heterogeneity of domains in these PPE based block copolymer offers important contributions these PPE based block copolymer offers important contributions to diverse applications. to diverse applications. Keywords: polyphenylene ether; compatibilizer; interface; polybutylene terephthalate; polystyrene; Keywords: polyphenylene ether; compatibilizer; interface; polybutylene terephthalate; polystyrene; hydrophobic; polyurethane; polyesters hydrophobic; polyurethane; polyesters

1. Introduction 1. Introduction Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) is an engineering thermoplastic. Engineering Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) is an engineering thermoplastic. Engineering thermoplastics comprise a special performance segment of synthetic plastic materials that offer thermoplastics comprise a special performance segment of synthetic plastic materials that offer enhanced properties. When properly formulated, they may be shaped into mechanically functional, enhanced properties. When properly formulated, they may be shaped into mechanically functional, semi-precision parts or structural components. Mechanically functional implies that the parts may semi-precision parts or structural components. Mechanically functional implies that the parts may be be subjected to mechanical stress, impact, flexure, vibration, sliding friction, temperature extremes, subjected to mechanical stress, impact, flexure, vibration, sliding friction, temperature extremes, hostile environments, etc., and continue to function. hostile environments, etc., and continue to function. The structure of PPE is depicted in Figure1. The principal repeat unit is the The structure of PPE is depicted in Figure 1. The principal repeat unit is the 2,6-dimethyl-1,4- 2,6-dimethyl-1,4-phenylene unit. At opposite ends of the polymer chain is a 2,6-dimethylphenoxy phenylene unit. At opposite ends of the polymer chain is a 2,6-dimethylphenoxy tail-group and a 3,5- tail-group and a 3,5-dimethyl-4-hydroxyphenyl head-group. It has a highly aromatic structure with dimethyl-4-hydroxyphenyl head-group. It has a highly aromatic structure with a stiff backbone, no a stiff backbone, no hydrolysable bonds and no polarizable groups. These structural features result in hydrolysable bonds and no polarizable groups. These structural features result in a polymer with a polymer with outstanding hydrolytic stability, very low moisture absorption, high glass transition outstanding hydrolytic stability, very low moisture absorption, high glass transition temperature temperature (Tg), low density, and very low dielectric properties [1–5]. PPE is used primarily in blends (Tg), low density, and very low dielectric properties [1–5]. PPE is used primarily in blends and alloys and alloys to enhance the thermal performance, increase toughness and lower moisture absorption of to enhance the thermal performance, increase toughness and lower moisture absorption of other other thermoplastics. thermoplastics.

Figure 1. Depiction of poly(2,6-dimethyl-1,4-phenylenepoly(2,6-dimethyl-1,4-phenylene ether) (PPE) chemical structure.

Polymers 2017, 9, 433; doi:10.3390/polym9090433 www.mdpi.com/journal/polymers Polymers 2017, 9, 433; doi:10.3390/polym9090433 www.mdpi.com/journal/polymers Polymers 2017, 9, 433 2 of 25 Polymers 2017, 9, 433 2 of 24 Polymers 2017, 9, 433 2 of 25 The very high molecular weight, high melt and solution viscosities, and low number of functional groups per molecule limits PPEs use as a reactive building block. However, unique PPE The veryvery high high molecular molecular weight, weight, high high melt melt and solutionand solution viscosities, viscosities, and low and number low ofnumber functional of telechelic macromonomers (PPE-M) have been developed for facile incorporation of PPE features into groupsfunctional per groups molecule per limits molecule PPEs limits useas PPEs a reactive use as buildinga reactive block. building However, block. However, unique PPE unique telechelic PPE various copolymers and thermosetting resins [6–9]. PPE-M has the features of PPE, plus very low macromonomerstelechelic macromonomers (PPE-M) have(PPE-M) been have developed been develope for faciled for incorporation facile incorporation of PPE features of PPE features into various into molecular weight, which increases its solubility in solvents and monomers and a functionality around copolymersvarious copolymers and thermosetting and thermosetting resins [6 –resins9]. PPE-M [6–9]. has PPE-M the features has the of features PPE, plus of PPE, very lowplus molecular very low two. PPE telechelic macromers have been heralded as a breakthrough in the search for materials that weight,molecular which weight, increases which increases its solubility its solubility in solvents in solvents and monomers and monomers and a and functionality a functionality around around two. broadly enhanced performance of dielectric materials [6–11]. The structure of PPE-M is depicted in PPEtwo. telechelicPPE telechelic macromers macromers have have been been heralded heralded as as a breakthrougha breakthrough in in the the search search for for materialsmaterials that Figure 2. Hydroxyl groups at each end of the oligomer facilitate use in thermoset resins and in the broadly enhanced performance of dielectric material materialss [6–11]. [6–11]. The structure of PPE-M is depicteddepicted in synthesis of linear high molecular weight copolymers. Figure2 2.. HydroxylHydroxyl groupsgroups atat eacheach endend ofof thethe oligomeroligomer facilitatefacilitate useuse inin thermosetthermoset resinsresins andand inin thethe synthesis of linear high molecular weightweight copolymers.copolymers.

Figure 2. Depiction of PPE telechelic macromonomers (PPE-M) chemical structure. Figure 2. Depiction of PPE telechelic macromonomers (PPE-M) chemical structure. Figure 2. Depiction of PPE telechelic macromonomers (PPE-M) chemical structure. Features of PPE with PPE-M are summarized in Table 1. PPE-M has a significantly lower number Features of PPE with PPE-M are summarized in Table1. PPE-M has a significantly lower number averageFeatures molecular of PPE weight with PPE-M(Mn), which are summarized translates to in greater Table 1. solubility PPE-M has in solvents. a significantly This high lower solubility, number average molecular weight (Mn), which translates to greater solubility in solvents. This high solubility, functionalityaverage molecular around weight two, (Mn), and lowwhich viscosity translates facilitates to greater the solubility use of PPE-M in solvents. in preparative This high solubility, polymer functionality around two, and low viscosity facilitates the use of PPE-M in preparative polymer chemistry.functionality The around hydroxyl two, equivalent and low weightviscosity (HEW) facilitates for PPE-M the use is ofmuch PPE-M lower in thanpreparative that of PPE.polymer The chemistry. The hydroxyl equivalent weight (HEW) for PPE-M is much lower than that of PPE. telechelicchemistry. nature The hydroxyl of PPE-M equivalent makes it usefulweight as (HEW) a cross-linker, for PPE-M chain is much extender, lower and than precursor that of PPE.for block The The telechelic nature of PPE-M makes it useful as a cross-linker, chain extender, and precursor for block andtelechelic graft naturecopolymers. of PPE-M The makeshydrophobicity it useful asof aPPE-M cross-linker, in thermoplastic chain extender, and thermosetand precursor resins for is block well and graft copolymers. The hydrophobicity of PPE-M in thermoplastic and thermoset resins is well documented.and graft copolymers. In addition, The from hydrophobicity its engineering of PPE-M thermoplastic in thermoplastic heritage and and judicious thermoset synthesis, resins is PPE-well documented. In addition, from its engineering thermoplastic heritage and judicious synthesis, PPE-M Mdocumented. can increase In addition,the thermal from properties its engineering and thertoughness,moplastic and heritage lower andthe judiciousdielectric synthesis, properties PPE- in can increase the thermal properties and toughness, and lower the dielectric properties in thermoplastic thermoplasticM can increase and the thermoset thermal resins. properties and toughness, and lower the dielectric properties in and thermoset resins. thermoplastic and thermoset resins. Table 1. Comparison of PPE and PPE-M. Table 1. Comparison of PPE and PPE-M. Property PPE PPE-M Property PPE PPE-M Mn,Property g/mol 15,000 PPE PPE-M 1670 HEW,Mn,Mn, g/mol g/equiv.g/mol 15,000 ~15,000 15,000 1670 1670 800 HEW, g/equiv. ~15,000 800 HEW,Tg, g/equiv. °C ~15,000 215 150800 Tg, ◦C 215 150 SolubilitySolubilityTg, at °Cat 25 25◦ C°C 215 150 Solubility2-Butanone at 25 °C <1%<1% >50%>50% 2-ButanoneToluene ~20%~20%<1% >50%>50% FunctionalityToluene ~20% ~1~1 >50% ~2~2 Functionality ~1 ~2 In addition to hydrophobicity, thethe PPE-MPPE-M domainsdomains havehave otherother philicities,philicities, whichwhich contributecontribute to uniqueIn propertyaddition combinationsto hydrophobicity, in block the copolymers.copolymers PPE-M domains. Amphiphilic have other block philicities, copolymers which (ABC) contribute have been to preparedunique property with hydrophilic combinations segments in block such copolymers as polyurethanes,poly.urethanes, Amphiphilic polyhydroxyethers block copolymers (phenoxy (ABC) have resins), been andprepared polyether with carbonateshydrophilic [[12–17].12 segments–17]. such as polyurethanes, polyhydroxyethers (phenoxy resins), and polyetherPolyhydroxy carbonates ethersethers (PHE) (PHE[12–17].) or or phenoxy phenoxy resins resins are are thermoplastics thermoplas thattics that were were an outgrowth an outgrowth of epoxy of resinepoxyPolyhydroxy technology resin technology [18 ethers]. The [18]. (PHE structure The) or stru isphenoxycture depicted is resinsdepicted in Figure are in 3thermoplas .Figure Structural 3. Structuraltics features that were includefeatures an ether outgrowthinclude linkages, ether of whichlinkages,epoxy provideresin which technology flexibility, provide [18].flexibility, and The pendant stru andcture hydroxyl pendant is depicted groups hydroxyl toin promoteFiguregroups 3. to wettingStructural promote and wettingfeatures hydrogen and include bonding hydrogen ether to polarbondinglinkages, substrates towhich polar andprovide substrates fillers. flexibility, The and first fill and halfers. pendantThe of this first review hydroxylhalf of focuses this groups review on the to focuses usepromote of PPE-M on wetting the to use make and of PPE-Mhydrogen PPE-PHE to amphiphilicmakebonding PPE-PHE to polar block amphiphilic substrates copolymers blockand to fill enhance copolymersers. The their first to performance enhancehalf of this their andreview performance expand focuses their andon utility. the expand use of their PPE-M utility. to make PPE-PHE amphiphilic block copolymers to enhance their performance and expand their utility.

Figure 3. Depiction of polyhydroxy ethe etherr (PHE) chemical structure. Figure 3. Depiction of polyhydroxy ether (PHE) chemical structure.

Polymers 2017, 9, 433 3 of 25 Polymers 2017, 9, 433 3 of 24 The second half of this paper reviews the use of PPE-M in thermoplastic polyurethanes (TPUs). TPUsThe are secondversatile half polymers of this paper with many reviews useful the use properties. of PPE-M However, in thermoplastic TPUs can polyurethanes have limited (TPUs).service TPUstemperature, are versatile high polymersmoisture withabsorption, many usefuland poor properties. resistance However, to burning. TPUs Clearly, can have the limited engineering service temperature,features of PPE-M high moistureand TPUs absorption, would be and complementary poor resistance in toa burning.block copolymer Clearly, theand engineeringpresent an featuresopportunity of PPE-M to enhance and TPUs the wouldperformance be complementary of TPUs. in a block copolymer and present an opportunity to enhance the performance of TPUs. 2. Materials and Methods 2. Materials and Methods 2.1. Preparation of Polyhydroxy Ethers 2.1. Preparation of Polyhydroxy Ethers To prepare stable, linear, high molecular weight PPE-PHE ABCs, some important synthetic techniquesTo prepare need stable,to be followed. linear, high These molecular critical steps weight are summarized PPE-PHE ABCs, in a general some important procedure synthetic below. techniquesThe PPE need telechelic to be followed. macromonomer These critical (PPE-M) steps (Mn are ~ summarized 1670) is available in a general from SABIC procedure LLC below. (Bergen op Zoom,The PPEThe Netherlands) telechelic macromonomer under NORYL™ (PPE-M) SA90 designation. (Mn ~1670) Experimental is available PPE-M from SABIC with Mn LLC of (Bergen2750 and op 1150 Zoom, wereThe supplied Netherlands) by SABIC under LLC NORYL (Bergen™ SA90 op Zoom, designation. The Netherlands). Experimental The PPE-M diglycidyl with Mnethers of 2750of bisphenol and 1150 A were (DGEBPA) supplied with by SABICvarious LLC epox (Bergeny equivalents op Zoom, were The obtained Netherlands). from Dow The diglycidylChemical ethers(Midland, of bisphenol MI, USA) A and (DGEBPA) Momentive with Specialty various epoxy Chemicals equivalents (Columbus, were obtainedOH, USA). from The Dow HEW, Chemical epoxy (Midland,equivalent MI,weight USA) (EEW) and Momentive and the Specialtyfunctionality Chemicals of PPE-M (Columbus, and DGEBPA, OH, USA). respectively, The HEW, epoxywere equivalentdetermined weight by nuclear (EEW) magnetic and the resonance functionality (NMR). of PPE-M and DGEBPA, respectively, were determined by nuclearAlternating magnetic block resonance copolymers (NMR). were prepared by the reaction of PPE-M with DGEBPA. The molecularAlternating weights block of copolymersthe PHE segments were prepared were calculated by the reaction by the of EEW PPE-M × functionality. with DGEBPA. The The molecular molecular weights ofof thethe PHE PPE segments segments were were calculated calculated by by the the EEW HEW× functionality. × functionality. The The molecular number weights average of themolecular PPE segments weight wereof the calculated PPE block by theand HEW the PHE× functionality. was varied The from number 1150 averageto 2750 molecularand 400 to weight 5000, ofrespectively. the PPE block The andPPE thecontent PHE in was the varied block copo fromlymers 1150 to was 2750 varied and400 from to 24 5000, to 80 respectively. wt %. The PPE contentKey in consideration the block copolymers for preparing was varied linear, from high 24 molecular to 80 wt %. weight block copolymers include 1:1 stoichiometryKey consideration of phenolic for to epoxy preparing groups linear, and highreactants molecular with a functionality weight block of copolymers 2. For good thermal include 1:1stability, stoichiometry the final of polymer phenolic should to epoxy not groups have andany reactantsunreacted with epoxy a functionality end groups. of 2.Another For good important thermal stability,consideration the final is avoiding polymer the should side notreactions have any inherent unreacted in epoxy epoxy resin end chemistry groups. Another where importantsecondary considerationalcohol groups is avoidingreact with the epoxy side reactions groups, inherentleading into epoxybranching resin [19,20]. chemistry For where example, secondary up to alcohol 11.9% groupsbranching react has with been epoxy reported groups, in leadingphenoxy to resins branching prepared [19,20 ].from For the example, reaction up of to 11.9%BPA with branching DGEBPA has been[21]. The reported branching in phenoxy reaction resins is shown prepared in Figure from the 4. reaction of BPA with DGEBPA [21]. The branching reaction is shown in Figure4.

Figure 4. Branching reaction in diglycidyl ethers of bisphenol A (DGEBPA). Figure 4. Branching reaction in diglycidyl ethers of bisphenol A (DGEBPA).

The reaction of the PPE-M phenolic groups with epoxyepoxy is significantlysignificantly faster than the reaction of alcohol groupsgroups with with epoxy epoxy [11 ].[11]. Therefore, Therefore, the synthesisthe synthesis involved involved programed programed addition addition of the DGEBPA of the

Polymers 2017, 9, 433 4 of 24 Polymers 2017, 9, 433 4 of 25 toDGEBPA a solution to ofa solution PPE-M so of that PPE-M there so was that always there anwas excess always of phenolic an excess groups. of phenolic The PPE-M groups. was The dissolved PPE-M inwas cyclohexanone dissolved in atcyclohexanone 150 ◦C. Using at 0.1 150 mole °C. % UsingN,N0-dimethylamino 0.1 mole % N,N pyridine′-dimethylamino as a catalyst, pyridine the epoxy as a wascatalyst, added the over epoxy 5–6 h.was After added cooling, over the 5–6 block h. After copolymer cooling, was the isolated block bycopolymer precipitation was inisolated methanol by andprecipitation dried. This in procedure methanol resulted and dried. in linear This polymers procedure with resulted <0.1% branching. in linear The polymers structure with appears <0.1% in 1 Figurebranching.5. 1H-NMR The structure 400 MHz appears monitored in Figure the disappearance5. H-NMR 400 of MHz methine monitored hydrogen the on disappearance the oxirane and of themethine appearance hydrogen methine on the hydrogen oxirane and of secondarythe appearance alcohol methine using. hydrogen NMR confirmed of secondary the absence alcohol ofusing. any NMR confirmed the absence of any unreacted epoxy. unreacted epoxy.

Figure 5. The general structure of PPE-PHE block copolymer. Figure 5. The general structure of PPE-PHE block copolymer. 2.2. Blends and Composites 2.2. Blends and Composites PBT (poly(butylene terephthalate)) was obtained as VALOX™ 315 from SABIC LLC. PPE, having PBT (poly(butylene terephthalate)) was obtained as VALOX™ 315 from SABIC LLC. PPE, an intrinsic viscosity of about 0.40 dL/g (deciliter per gram) as measured in chloroform at 25 ◦C having an intrinsic viscosity of about 0.40 dL/g (deciliter per gram) as measured in chloroform at 25 was obtained as PPO™ 640 from SABIC LLC. SEBS, polystyrene-poly(ethylene-butylene)-polystyrene °C was obtained as PPO™ 640 from SABIC LLC. SEBS, polystyrene-poly(ethylene-butylene)- triblock copolymer having a polystyrene content of about 30% was obtained as KRATON™ G1650M polystyrene triblock copolymer having a polystyrene content of about 30% was obtained as from Kraton Performance Polymers Inc (Houston, TX, USA). PHE resin was obtained as PKHH™ from KRATON™ G1650M from Kraton Performance Polymers Inc (Houston, TX, USA). PHE resin was Gabriel Performance Products (Akron, OH, USA). Formulations are summarized in Table2. obtained as PKHH™ from Gabriel Performance Products (Akron, OH, USA). Formulations are summarized in Table 2. Table 2. Composition of PBT/PPE/SEBS blends.

PBT,Table wt % 2. Composition PPE, wt % of PBT/PPE/SEBS SEBS, wt % blends. PHE, wt % ABC-36, wt %

Blend PBT,40 wt % PPE, 48 wt % SEBS, 12 wt % PHE, - wt % ABC-36, - wt % Blend withBlend PHE 4040 4048 10 12 10 - - - Blend with Blend with PHE 4040 4040 10 10 10 - -10 ABC-36 Blend with ABC-36 40 40 10 - 10

PS (atactic polystyrene), was obtained as STYRONSTYRON™™ 685DL from AmericasAmericas StyrenicsStyrenics LLC (Torrance,(Torrance, CA,CA, USA).USA). ChoppedChopped glassglass fiberfiber (GF)(GF) havinghaving aa diameterdiameter ofof aboutabout 1010 micrometers,micrometers, aa lengthlength of aboutabout 3.23.2 mm,millimeters, and a γ-amino-propyl-silane and a γ-amino-propyl-silane surface treatment surface trea wastment obtained was asobtained E-Glass as Chopped E-Glass StrandChopped from Strand Nippon from Electric Nippon Glass Electric Company Glass Company (Otsu, Japan). (Otsu, Formulations Japan). Formulations are summarized are summarized in Table3. in Table 3. Table 3. Composition of GF PS/PPE. Table 3. Composition of GF PS/PPE. Designation PS, wt % GF, wt % PHE, wt % ABC-36, wt % Designation PS, wt % GF, wt % PHE, wt % ABC-36, wt % PS/GF 80 20 0 0 PS/GF/PHEPS/GF 7580 2020 5 0 0 0 PS/GF/ABC-36PS/GF/PHE 7575 2020 0 5 0 5 PS/GF/ABC-36 75 20 0 5

Blends were compounded on a Coperion ZSK 18 twin-screw laboratory extruder (18 mm screw Blends were compounded on a Coperion ZSK 18 twin-screw laboratory extruder (18 millimeters outer diameter) operating at a screw rotation rate of 300 revolution per minute and zone temperatures screw outer diameter) operating at a screw rotation rate of 300 revolution per minute and zone of 180, 230, 260, 270, 270, 270, and 270 ◦C from feed throat to die. Parts for physical property temperatures of 180, 230, 260, 270, 270, 270, and 270 °C from feed throat to die. Parts for physical determination were obtained by injection molded using a Demag Plastic Group Model 40–80 injection property determination were obtained by injection molded using a Demag Plastic Group Model 40– molding machine (Strongsville, OH, USA). 80 injection molding machine (Strongsville, OH, USA). 2.3. Preparation of Thermoplastic Polyurethanes 2.3. Preparation of Thermoplastic Polyurethanes Relative to typical polyurethane building blocks, the PPE-M has phenolic end groups and is a solid Relative to typical polyurethane building blocks, the PPE-M has phenolic end groups and is a with a high Tg and softening point as indicated in Table1. Some challenges for the use of PPE-M to solid with a high Tg and softening point as indicated in Table 1. Some challenges for the use of PPE- M to prepare PPE-based TPUs were how to handle the solid PPE-M in typical urethane synthetic

Polymers 2017, 9, 433 5 of 24 Polymers 2017, 9, 433 5 of 25 prepareprocedures PPE-based and understanding TPUs were how the toreactivity handle theof the solid PPE PPE-M phenolic in typical end group urethane with synthetic isocyanates. procedures Below anda general understanding procedure the summarizes reactivity ofthe the process PPE phenolic and chemistry end group details with for isocyanates. the facile synthesis Below a generalof PPE- procedurebased TPUs. summarizes the process and chemistry details for the facile synthesis of PPE-based TPUs. EthyleneEthylene oxide-capped oxide-capped oxypropylated oxypropylated polyether polyether diol, diol, EO-PO, EO-PO, (OH (OH = 56.7 = 56.7mgKOH/g) mgKOH/g) was Poly- was Poly-GG™ 55–56™ 55–56supplied supplied by Arch by Chemicals, Arch Chemicals, Inc (Norwalk, Inc (Norwalk,CT, USA). 4,4 CT,′-Diphenylmethane USA). 4,40-Diphenylmethane diisocyanate, diisocyanate,4,4′-MDI, (NCO% 4,40-MDI, = 33.6%, (NCO% eq. =wt. 33.6%, 125.06) eq. was wt. Mondur™ 125.06) was M Mondurfrom Covestro™ M from AG Covestro(Leverkusen, AG (Leverkusen,Germany). The Germany). chain extender The chain was 1,4-butandiol, extender was BD, 1,4-butandiol, (Eq. wt. = 45) BD, from (Eq. Alfa wt. Aesar = 45) from(Ward Alfa Hill, Aesar MA, (WardUSA). Hill,Dibutyl-tin MA, USA). dilaurate, Dibutyl-tin DBTDL, dilaurate, catalyst DBTDL,was Dabco™ catalyst T-12 was from Dabco Air ™ProductsT-12 from (Allentown, Air Products PA, (Allentown,USA). PA, USA). TheThe solubility/compatibilitysolubility/compatibility of of PPE-M PPE-M was was determined determined in in a wide variety of polyolspolyols andand chainchain extenders.extenders. In general, the PPE-M exhibited good solubility and compatibility with polyether polyols. Soluble,Soluble, homogeneoushomogeneous blendsblends of PPE-M and EO-PO were liquids with Tgs below room temperature. TheseThese homogeneoushomogeneous liquidliquid blendsblends providedprovided aa convenientconvenient routeroute forfor incorporationincorporation ofof PPE-MPPE-M intointo thethe TPUTPU polymerizationpolymerization process.process. TheThe reactionreaction ofof thethe phenolicphenolic groups of PPE-M with isocyanate groups is depicted in Figure 66.. TheThe raterate ofof reactionsreactions ofof PPE-MPPE-M withwith 4,4 4,40-MDI′-MDI (0.13(0.13 mol/kg mol/kg andand 0.150.15 mol/kg,mol/kg, respectively)respectively) werewere measuredmeasured inin toluene toluene at 50at ◦C50 and °C 70and◦C. The70 °C. reactions The reactions were monitored were bymonitored measuring by the measuring concentration the ofconcentration unreacted isocyanate of unreacted group isocyanate via standard group di-n-butylamine via standard di-n-butylamine titration method titration [22]. The method PPE-M [22]. readily The reactsPPE-M with readily the isocyanatereacts with groups.the isocyanate The reactions groups. followed The reactions second followed order kinetics second up order to high kinetics degree up ofto isocyanatehigh degree conversion. of isocyanate The conversion. reaction mixtures The reaction remained mixtures as aremained single phase as a single liquid phase during liquid the kineticduring measurements.the kinetic measurements. The rate of reaction The rate increased of reaction with in increasedcreased reactionwith increased temperature. reaction In addition,temperature. the use In ofaddition, DBTDL the (0.01%) use of resulted DBTDL in(0.01%) a significant resulted increase in a sign inificant the rate. increase Kinetic in the data rate. is shownKineticgraphically data is shown in Figuregraphically7. in Figure 7.

FigureFigure 6.6. Reaction of PPE-M with isocycanate group.group.

Figure 7. Rate of reaction of PPE-M with MDI. Figure 7. Rate of reaction of PPE-M with MDI. The formulations for preparing PPE-M/EO-PO based TPUs appear in Table4. The object was The formulations for preparing PPE-M/EO-PO based TPUs appear in Table 4. The object was to to determine the performance features of TPUs as the hydrophobic content changed with increasing determine the performance features of TPUs as the hydrophobic content changed with increasing amounts of PPE-M. The weight ratio of PPE-M to EO-PO was 0/100, 10/90, 20/80, and 30/70 and the amounts of PPE-M. The weight ratio of PPE-M to EO-PO was 0/100, 10/90, 20/80, and 30/70 and the content of hydrophobic PPE-M segments was 0, 7.65, 15.29, and 23 weight %. There was no attempt to content of hydrophobic PPE-M segments was 0, 7.65, 15.29, and 23 weight %. There was no attempt optimize any of the formulations. to optimize any of the formulations.

PolymersPolymers 20172017, 9, ,9 433, 433 6 6of of 25 24

Table 4. Formulations for PPE-M/EO-PO based TPUs. Polymers 2017, 9, 433 Table 4. Formulations for PPE-M/EO-PO based TPUs. 6 of 25 PPE-M, wt % EO-PO, wt % 4,4′-MDI, wt % BD, wt % DBTDL, phr PPE-M,0 wt %Table EO-PO,76.70 4. Formulations wt % 4,4 for0-MDI,19.99 PPE-M/EO-PO wt % BD,based3.31 wt TPUs. % DBTDL,0.0089 phr 7.65 68.89 19.95 3.51 0.0038 PPE-M,0 wt % EO-PO,76.70 wt % 4,4′-MDI, 19.99 wt % BD, 3.31 wt % DBTDL, 0.0089 phr 15.297.65 0 61.1768.8976.70 20.02 19.9519.99 3.31 3.513.52 0.0089 0.00380.0013 23.0015.297.65 53.6761.1768.89 20.34 20.0219.95 3.51 3.522.99 0.0038 0.00130.0027 23.0015.29 53.6761.17 20.3420.02 3.52 2.99 0.0013 0.0027 TPUs were prepared23.00 via bulk polymerization,53.67 where20.34 the PPE-M2.99 was pre-dissolved0.0027 in the polyol. At 100TPUs °C, MDI were (warmed prepared to via 80 bulk°C) was polymerization, added via syri wherenge to the the PPE-M mixture was of pre-dissolved polyols, BD, and in the DBTDL polyol. catalystAt 100 ◦(~0.003C,TPUs MDI werephr) (warmed preparedand mixed to 80via ◦ bulkviaC) wasa polymerization, Speed added Mixe viar syringe(2200where rpm)the to PPE-M the for mixture 30–40 was pre-dissolved s of and polyols, then transferredin BD, the and polyol. DBTDL to a At 100 °C, MDI (warmed to 80 °C) was added via syringe to the mixture of polyols, BD, and DBTDL preheatedcatalyst (~0.003 mold at phr) 120 °C. and The mixed TPUs via were a Speed cured Mixerfor 2 h (2200at 120 rpm) °C and for then 30–40 post-cured s and then for 20 transferred h at 100 catalyst (~0.003 phr) and mixed via a Speed Mixer (2200 rpm) for 30–40 s and then transferred to a °C.to FTIR a preheated spectra of mold cured at TPUs 120 ◦ C.indicated The TPUs that werepolymerizations cured for 2 were h at completed; 120 ◦C and there then was post-cured no or only for preheated mold at 120 °C. The TPUs were cured for 2 h at 120 °C and then post-cured for 20 h at 100 traces amounts◦ of unreacted isocyanate (-NCO groups) at 2270 cm−1. The general synthesis of PPE- 20 h at°C. 100 FTIRC spectra. FTIR of spectra cured TPUs of cured indicated TPUs that indicated polymerizations that polymerizations were completed; were there completed; was no or thereonly was −1 M/EO-POno ortraces only based tracesamounts TPUs amounts of areunreacted shown of unreacted isocyanate in Figure isocyanate (-NCO 8. groups) (-NCO at groups) 2270 cm at−1. 2270The general cm . Thesynthesis general of PPE- synthesis of PPE-M/EO-POM/EO-PO based based TPUs TPUs are shown are shown in Figure in 8. Figure 8.

FigureFigure 8. General 8. General structure structure of of segments segments inin PPE-MPPE-M based based TPUs. TPUs. Figure 8. General structure of segments in PPE-M based TPUs. 3. Results3. Results 3. Results 3.1. Properties of PPE-PHE Block Copolymers 3.1.3.1. Properties Properties of of PPE-PHE PPE-PHE Block Block Copolymers Copolymers Over the range studied using PPE-M with a Mn of 1670, the PPE-PHE block copolymers Over the range studied using PPE-M with a Mn of 1670, the PPE-PHE block copolymers Overexhibited the rangea single studied Tg which using increased PPE-M with with increased a Mn of 1670,levels theof PPE-M PPE-PHE as shown block in copolymers Figure 9. PHEs exhibited exhibited a single Tg which increased with increased levels of PPE-M as shown in Figure 9. PHEs a singlehave Tg relatively which increased low Tgs around with increased 90 °C and levelsend use of temperatures PPE-M as shown are restricted in Figure to 9about. PHEs 60–80 have °C relatively [12]. havelow TgsrelativelyWith around the higherlow 90 Tgs◦ CTgs andaround (>100 end °C),90 use °C temperaturesPPE-PHE and end block use are temperaturescopolymers restricted offer to are about opportunitiesrestricted 60–80 ◦toC[ aboutin12 adhesives]. With 60–80 the °Cand higher [12]. WithTgs (>100thecoatings higher◦C), where PPE-PHE Tgs >80 (>100 °C block use°C), copolymerstemper PPE-PHEatures offerblock are required. opportunities copolymers The effect inoffer adhesives of opportunities molecular and coatingsweight in adhesives on where Tg was>80 and◦C coatingsuse temperaturesstudied where in copolymers>80 are°C required.use containing temper Theatures about effect are48 of wtrequired. molecular % PPE-M. The The weight effect results on of in Tgmolecular Figure was studied10 showweight a in single on copolymers Tg Tg was studiedcontainingwhich in copolymers aboutincreased 48 wtwith containing % increased PPE-M. about Themolecular results48 wt weight% in PPE-M. Figure of PPE-M. 10The show results Except a single in where Figure Tg noted, which10 show most increased a ofsingle the with Tg evaluations in this review were done with PPE-PHE block copolymers with PPE-M with a Mn of whichincreased increased molecular with weight increased of PPE-M. molecular Except weight where noted,of PPE-M. most ofExcept the evaluations where noted, in this most review of werethe 1670. evaluationsdone with PPE-PHEin this review block were copolymers done with with PPE- PPE-MPHE with block a Mn copolymers of 1670. with PPE-M with a Mn of 1670.

Figure 9. Tg versus PPE-M (Mn 1670) Content.

Figure 9. Tg versus PPE-M (Mn 1670) Content. Figure 9. Tg versus PPE-M (Mn 1670) Content.

Polymers 2017, 9, 433 7 of 25 Polymers 2017, 9, 433 7 of 25 Polymers 2017, 9, 433 7 of 24 Polymers 2017, 9, 433 7 of 25

FigureFigure 10. 10. Tg Tg versus versus Mn Mn of of PPE-M PPE-M segments segments (48 (48 wt wt %). %). Figure 10. Tg versus Mn of PPE-M segments (48 wt %). Figure 10. Tg versus Mn of PPE-M segments (48 wt %). WaterWater absorption absorption in in polymers polymers is is known known to to have have adverse adverse effects effects on on dimensional dimensional stability, stability, Tg, Tg, and and Water absorption in polymers is known to have adverse effects on dimensional stability, Tg, mechanicalmechanicalWater absorptionproperties. properties. inThe The polymers alcohol alcohol isgroups groups known on on to PHE havePHE can adversecan hydrogen hydrogen effects bond bond on dimensional to to water. water. However, However, stability, the Tg,the PPEandPPE and mechanical properties. The alcohol groups on PHE can hydrogen bond to water. However, segmentsmechanicalsegments dodo properties. notnot containcontain The polaralcoholpolar groups,groups, groups which onwhich PHE wowo canulduld hydrogen stronglystrongly bond hydrogenhydrogen to water. bondbond However, toto water,water, the and,PPEand, the PPE segments do not contain polar groups, which would strongly hydrogen bond to water, correspondingly,segmentscorrespondingly, do not have havecontain very very polarlow low water watergroups, absorption. absorption. which woPPE-PHE PPE-PHEuld strongly block block copolymerscopolymershydrogen bondimmersed immersed to water, in in water water and, at at and, correspondingly, have very low water absorption. PPE-PHE block copolymers immersed in water 80correspondingly,80 °C °C exhibited exhibited weight weight have veryincreases increases low water over over time. absorption.time. As As sh shown ownPPE-PHE in in Figure Figure block 11, 11, copolymers there there was was a immerseda significant significant in decrease waterdecrease at at 80 ◦C exhibited weight increases over time. As shown in Figure 11, there was a significant decrease in80in water °Cwater exhibited absorption absorption weight with with increases increasing increasing over levels levels time. of of As PPE-M. PPE-M. shown in Figure 11, there was a significant decrease in water absorption with increasing levels of PPE-M. in water absorption with increasing levels of PPE-M.

Figure 11. Water uptake versus PPE-M content. FigureFigure 11. 11. Water Water uptake uptake versus versus PPE-M PPE-M content. content. Figure 11. Water uptake versus PPE-M content. Interestingly,Interestingly, the thethe PHE PHEPHE control controlcontrol sample samplesample distorted distorteddistorted in in less lessless than thanthan 90 9090 h hh of ofof immersion, immersion,immersion, as asas shown shownshown in inin FigureFigureInterestingly, 12. 12.12 .This This This suggests suggests suggests the PHE that that that controlthe the the absorbed absorbed absorbed sample water water waterdistorted plasticized plasticized plasticized in less the the than the PHE PHE PHE90 and andh andof depressed depressed immersion, depressed the the theasTg Tg shownbelow Tgbelow below 80 in80 ◦ °C.Figure80°C. Hence, Hence,C. 12. Hence, Thisthe the thepart suggestspart part distorted. distorted. distorted. that the absorbed water plasticized the PHE and depressed the Tg below 80 °C. Hence, the part distorted.

FigureFigure 12. 12. Test Test parts parts before before and and after after 90 90 h h immersion immersion in in water. water. Figure 12. Test parts before and after 90 h immersion in water. InIn dry drydry samples, samples,samples, the the flexural flexuralflexural modulus modulus (FM) (FM) incr increasedincreasedeased slightly slightly withwith increasingincreasing PPE-MPPE-M content.content. ◦ However,However,In dry after after samples, 16 16 h hh immersion immersionimmersionthe flexural in inin modulus water waterwater at atat (FM)80 8080 °C, °C,C, incr the thetheeased FMs FMsFMs decreased. decreased.slightlydecreased. with This ThisThis increasing corresponds correspondscorresponds PPE-M to to moisture moisturemoisturecontent. However, after 16 h immersion in water at 80 °C, the FMs decreased. This corresponds to moisture

Polymers 20172017,, 9,, 433 433 88 of of 25 24 Polymers 2017, 9, 433 8 of 25 uptake which acts as a plasticizer. PHE exhibited the greatest decrease. The PPE-PHE block uptakecopolymersuptake which exhibited actsacts as as a much plasticizer.a plasticizer. greater PHE rete PHE exhibitedntion exhi of thebitedFM greatestas theshown greatest decrease. in Figure decrease. The 13. PPE-PHE The blockPPE-PHE copolymers block copolymersexhibited much exhibited greater much retention greater of rete FMntion as shown of FM in as Figure shown 13 in. Figure 13.

Figure 13. Effect of water uptake on flexural modulus. FigureFigure 13. 13. EffectEffect of of water water uptake uptake on on flexural flexural modulus. modulus. Flexural strengths (FS) in dry samples exhibited a slight decrease with increasing PPE-M content. Flexural strengths (FS) in dry samples exhibited a slight decrease with increasing PPE-M content. The FlexuralFSs decreased strengths after (FS) 16 hin immersion dry samples in exhibited water at 80a slight °C. PHE decrease exhibited with theincreasing greatest PPE-M decrease content. in FS. The FSs decreased after 16 h immersion in water at 80 ◦C. PHE exhibited the greatest decrease in TheThe FSs PPE-PHE decreased block after copolymers 16 h immersion exhibited in water much at grea 80 °C.ter PHEretention exhibited of FS the than greatest the PHE decrease as shown in FS. in FS. The PPE-PHE block copolymers exhibited much greater retention of FS than the PHE as shown TheFigure PPE-PHE 14. block copolymers exhibited much greater retention of FS than the PHE as shown in Figurein Figure 14. 14 .

Figure 14. Effect of water uptake on flexural strength. Figure 14. Effect of water uptake on flexural strength. Figure 14. Effect of water uptake on flexural strength. 3.2. Blends, Alloys, and Composites of PPE-PHE Block Copolymers 3.2. Blends, Alloys, and Composites of PPE-PHE Block Copolymers 3.2. Blends,The PPE-PHE Alloys, and amphiphilic Composites block of PPE-PHE copolymers Block representCopolymers an interesting class of polymers that have The PPE-PHE amphiphilic block copolymers represent an interesting class of polymers that have other useful philicities. High molecular weight PPE and PHE polymers will form miscible blends with otherThe useful PPE-PHE philicities. amphiphilic High molecular block copo weightlymers PPErepresent and PHE an interesting polymers class will ofform polymers miscible that blends have polystyrene and polyesters, respectively. Hence, the PPE block is polystyrene-philic and the PHE block otherwith polystyreneuseful philicities. and polyesters, High molecular respectively. weight HencPPE ande, the PHE PPE polymers block is polystyrene-philicwill form miscible andblends the is polyester-philic. In addition, the PHE contains hydroxyl groups to facilitate hydrogen bonding. withPHE polystyreneblock is polyester-philic. and polyesters, In addition,respectively. the PHEHenc containse, the PPE hydroxyl block is groups polystyrene-philic to facilitate hydrogen and the The polyphilic nature of these block copolymers can offer utility as interfacial agents in polymer blends PHEbonding. block The is polyester-philic. polyphilic nature In addition,of these block the PHE copolymers contains canhydroxyl offer utilitygroups as to interfacialfacilitate hydrogen agents in and alloys and in composites [23,24]. bonding.polymer blendsThe polyphilic and alloys nature and inof composites these block [23,24]. copolymers can offer utility as interfacial agents in Most polymer–polymer blends usually form immiscible blends that have unacceptable polymerMost blends polymer–polymer and alloys and inblends composites usually [23,24]. form immiscible blends that have unacceptable properties [25]. In addition, their morphology is unstable and can change with processing conditions. propertiesMost [25].polymer–polymer In addition, their blends morphology usually is formunstable im miscibleand can changeblends with that processing have unacceptable conditions. Compatibilization technology is used to improve the interfacial adhesion between the two phases, propertiesCompatibilization [25]. In addition, technology their is morphology used to improve is unstable the interfacial and can changeadhesion with between processing the twoconditions. phases, enhance properties, and give a stable morphology [25–27]. Block or graft copolymers with the Compatibilizationenhance properties, technology and give is a used stable to morphologyimprove the interfacial[25–27]. Block adhesion or graft between copolymers the two with phases, the appropriate structure can be used to promote adhesion at the interface [25–29]. Amphiphilic block enhanceappropriate properties, structure and can give be used a stable to promote morphology adhesion [25–27]. at the Block interface or graft[25–29]. copolymers Amphiphilic with block the copolymers can be useful compatibilizers, modifiers, adhesion promoters, and interfacial agents. appropriatecopolymers structurecan be useful can compatibilizers,be used to promote modifiers, adhesion adhesion at the promoters,interface [25–29]. and interfacial Amphiphilic agents. block The The PPE-PHE ABC would have an affinity for two different types of environments. The polyester-philic copolymersPPE-PHE ABC can wouldbe useful have compatibilizers, an affinity for modifiers, two differ adhesionent types promoters,of environments. and interfacial The polyester-philic agents. The and PPE-philic segments suggest utility as a compatibilizing agent in polyester/PPE blends. PPE-PHEand PPE-philic ABC would segments have suggest an affinity utility for as two a compatibilizing different types agent of environments. in polyester/PPE The polyester-philicblends. and PPE-philic segments suggest utility as a compatibilizing agent in polyester/PPE blends.

Polymers 2017, 9, 433 9 of 24

3.2.1. Alloys with Poly(butylene terephthalate) In this review, the term polymer alloy will refer to an immiscible polymer blend having a modified interface and/or morphology [25,27–29]. Alloys of semi-crystalline and amorphous polymer are particularly attractive. The key to unique alloys is to leverage key attributes from both polymers. In general,Polymers semi-crystalline 2017, 9, 433 polymers have chemical resistance and low melt viscosity.9 of Amorphous 25 polymers can provide dimensional stability, freedom from warpage, and improved impact strength [25]. 3.2.1. Alloys with Poly(butylene terephthalate) Alloys of poly(butylene terephthalate) (PBT) and PPE are of particular interest. Features of PBT include chemical resistanceIn this review, and good the term processability, polymer alloy however, will refer to the an Tgimmiscible around polymer 34 ◦C resultsblend having in dimensional a modified interface and/or morphology [25,27–29]. Alloys of semi-crystalline ◦and amorphous polymer changes atare relatively particularly low attractive. temperatures The key to [30 unique,31]. alloys PPE hasis to aleverage Tg above key attributes 200 C, from good both dimensional polymers. stability and propertiesIn general, at elevated semi-crystalline temperatures, polymers have but ischemical more difficultresistance toand process low melt [ 30viscosity.,31]. Amorphous PPE blendspolymers withcan provide polyesters dimensional are immisciblestability, freedom [30 from,31]. warpage, Hence, and compatibilization improved impact strength technology is essential for[25]. improving Alloys of poly(butylene the interfacial terephthalate) adhesion (PBT) between and PPEthe are of two particular phases interest. to give Features a stable of PBT morphology include chemical resistance and good processability, however, the Tg around 34 °C results in and in achievingdimensional broad changes enhancement at relatively of low useful temperatures properties. [30,31]. PPE has a Tg above 200 °C, good In polymerdimensional blends, stability PHE and forms properties miscible at elevated blends temperatures, with a variety but is more of polar difficult polymers, to process such[30,31]. as aliphatic and semi-aromaticPPE blends polyesters with polyesters [32–37 are]. Theimmiscible secondary [30,31]. alcoholHence, compatibilization groups on PHE technology can take is part in interactionsessential with polarfor improving polymers, the interfacial which seemadhesion to between be in the the origin two phases of miscibility to give a stable and morphology compatibility with and in achieving broad enhancement of useful properties. polar polymersIn [polymer38,39]. blends, PHE formsPHE forms miscible miscible blends blends with with a variety PBT [ of39 polar]. However, polymers, PHEssuch as arealiphatic incompatible with non-polarand semi-aromatic polymers suchpolyesters as PPE [32–37]. [40]. The Thus, second theary unique alcohol PPE-PHE groups on ABC PHE has can segmentstake part in that would facilitate attractioninteractions to with both polar phases. polymers, which seem to be in the origin of miscibility and compatibility with PBT/PPEpolar compositionspolymers [38,39]. were PHE summarizedforms miscible inblends Table with2. AllPBT blends [39]. However, contained PHEs 40 are wt incompatible % PBT. The 10 wt % with non-polar polymers such as PPE [40]. Thus, the unique PPE-PHE ABC has segments that would SEBS impactfacilitate modifier attraction would to both reside phases. in the PPE phase. Control compositionsPBT/PPE compositions included were PBTsummarized by itself in Table and 2. the All use blends of PHEcontained as a40 compatibilizer. wt % PBT. The 10 The ABC made withwt 36 % wtSEBS % impact PPE-M modifier was used would in reside these in evaluationsthe PPE phase. and has the designation ABC-36. In general, polyesters containControl a compositions transesterification included catalyst.PBT by itself Therefore, and the use to of preventPHE as a PBT-PHEcompatibilizer. catalyzed The ABC exchange made with 36 wt % PPE-M was used in these evaluations and has the designation ABC-36. In general, reactions, anhydrouspolyesters contain sodium a transesterification phosphate monobasic catalyst. Therefore, (0.3 wt %)to prevent was added PBT-PHE to quenchingcatalyzed exchange the catalyst [41]. Microscopyreactions, (STEMsanhydrous 2000 sodium×) phosphate shows themonobasic effectiveness (0.3 wt %) ofwas the added PPE-PHE to quenching block the catalyst copolymers as a compatibilizer[41]. between PPE and PBT phases. PBT is the continuous phase (light) and the PPE/SEBS is the dispersedMicroscopy domains (STEMs (dark). 2000×) The morphologyshows the effectiv of PBT/PPE/SEBSeness of the PPE-PHE control block in copolymers Figure 15 asa showsa very compatibilizer between PPE and PBT phases. PBT is the continuous phase (light) and the PPE/SEBS large PPE/SEBSis the dispersed domains. domains On the (dark). other The hand, morphology the morphology of PBT/PPE/SEBS of alloy control containing in Figure 15a ABC-36 shows very in Figure 15b reveals significantlylarge PPE/SEBS smaller, domains. well-dispersed On the other hand, PPE/SEBS the morphology domains. of alloy containing These micrographs ABC-36 in Figure suggest that the ABCs15b are reveals interacting significantly with smaller, both well-dispersed PBT and PPE PPE/SEBS phases, domains. which These should micrographs translate suggest to enhancement that of properties.the ABCs are interacting with both PBT and PPE phases, which should translate to enhancement of properties.

(a) (b)

Figure 15. Morphology of poly(butylene terephthalate)-PPE (PBT-PPE) blends: (a) uncompatibilized; Figure 15. a andMorphology (b) compatibilized of poly(butylene with amphiphilic terephthalate)-PPE block copolymers (ABC-36). (PBT-PPE) blends: ( ) uncompatibilized; and (b) compatibilized with amphiphilic block copolymers (ABC-36). A hallmark of PPE blends and alloys is the increase in thermal properties. As seen in Figure 16, A hallmarkPBT has ofa low PPE heat blends deflection and temperature alloys is the(HDT) increase at 1.82 MPa. in thermal However, properties. the PBT/PPE/SEBS As seen blends in Figure 16, PBT has awith low and heat without deflection ABC-36 temperature exhibited significant (HDT) incr ateases 1.82 in MPa.the HDT. However, The HDT of the the PBT/PPE/SEBS blend with PHE blends decreased which could be the result of the lower Tg of PHE. with and without ABC-36 exhibited significant increases in the HDT. The HDT of the blend with PHE decreased which could be the result of the lower Tg of PHE. Polymers 2017, 9, 433 10 of 25

Polymers 2017, 9, 433 10 of 24

Polymers 2017, 9, 433 10 of 25

Polymers 2017, 9, 433 10 of 25

Figure 16. HeatFigure deflection 16. Heat deflection temperature temperature (HDT) (HDT) of of PBT PBT and PBT/PPE and PBT/PPE Blends. Blends. Figure 16. Heat deflection temperature (HDT) of PBT and PBT/PPE Blends. Notched Izod (NI) impact strength for the blend containing ABC-36 is significantly higher than NotchedNotched Izodwithout Izod (NI) any (NI) impact compatibilizer impact strength strength or PHE, for as for shown the the blend in blend Figure containing containing 17. ABC-36 is is significantly significantly higher higher than than withoutwithout any compatibilizer any compatibilizer or PHE, or PHE, as shownas shown in in Figure Figure 17 17.. Figure 16. Heat deflection temperature (HDT) of PBT and PBT/PPE Blends.

Notched Izod (NI) impact strength for the blend containing ABC-36 is significantly higher than without any compatibilizer or PHE, as shown in Figure 17.

Figure 17. Notched Izod (NI) of PBT/PPE/SEBS Blends.

The effect of the molecular weight of the PPE-M segments in the ABC on impact strength appears in Figure 18. The Mn of the PPE-M segments was 1150, 1670, and 2750 and the PPE-M content in the ABC was 48 wt %. All alloys were made with 10 wt % ABC. The impact strength increases with increasing length of the PPE segment. This suggests increased interaction between the PPE-M FigureFigure 17. Notched 17. Notched Izod Izod (NI) (NI) of of PBT/PPE/SEBS PBT/PPE/SEBS Blends. Blends. segments of the ABC and the PPE dispersed phase. The effectThe effect of the of molecular the molecularFigure weight weight 17. Notched of theof the PPE-MIzod PPE-M (NI) of segments segments PBT/PPE/SEBS in the Blends. ABC ABC on on impact impact strength strength appears appears in Figurein Figure 18. The 18. The Mn Mn of theof the PPE-M PPE-M segments segments was 1150, 1150, 1670, 1670, and and 2750 2750 and andthe PPE-M the PPE-M content content in the in The effect of the molecular weight of the PPE-M segments in the ABC on impact strength appears ABC was 48 wt %. All alloys were made with 10 wt % ABC. The impact strength increases with the ABC wasin Figure 48 wt 18. %. The All Mn alloys of the PPE-M were segments made with was 101150, wt 1670, % ABC.and 2750 The and impact the PPE-M strength content increasesin the with increasing length of the PPE segment. This suggests increased interaction between the PPE-M increasingABC length was of 48 the wt PPE %. All segment. alloys were This made suggests with 10 increased wt % ABC. interaction The impact betweenstrength increases the PPE-M with segments segments of the ABC and the PPE dispersed phase. of the ABCincreasing and the length PPE dispersed of the PPEphase. segment. This suggests increased interaction between the PPE-M segments of the ABC and the PPE dispersed phase.

Figure 18. NI versus Mn of PPE-M segments in ABC.

A possible mechanism of property improvement with the use of ABCs is depicted in Figure 19. Without the PPE-PHE block copolymers, there is essentially little to no adhesion between PBT and PPE phases. Under stress a crack would propagate through the continuous phase and around the

FigureFigure 18. 18. NI versus Mn of PPE-M segments in ABC. Figure 18.NI NI versus versus Mn Mn of of PPE-M PPE-Msegments segments in in ABC. ABC. A possible mechanism of property improvement with the use of ABCs is depicted in Figure 19. A possibleWithoutA possible mechanism the PPE-PHEmechanism ofblock property of copolymers,property improvement improvement there is essentially withwith little the use to no of of adhesion ABCs ABCs is between isdepicted depicted PBT in andFigure in Figure 19. 19. WithoutWithout thePPE PPE-PHE phases.the PPE-PHE Under block stressblock copolymers, a copolymers, crack would there propagatethere is is essentially e ssentiallythrough the littlelittle continuous to no no adhesion adhesionphase and between around between the PBT PBT and and PPE phases. Under stress a crack would propagate through the continuous phase and around the PPE phases. Under stress a crack would propagate through the continuous phase and around the PPE/SEBS domain. However, with PPE-PHE block copolymers there is increased interfacial adhesion between the phases, the crack would propagate into the PPE/SEBS domain, and the stresses dissipated. Polymers 2017, 9, 433 11 of 25

PPE/SEBSPolymers 2017 domain., 9, 433 However, with PPE-PHE block copolymers there is increased interfacial adhesion11 of 25 Polymers 2017, 9, 433between the phases, the crack would propagate into the PPE/SEBS domain, and the stresses 11 of 24 dissipated.PPE/SEBS domain. However, with PPE-PHE block copolymers there is increased interfacial adhesion between the phases, the crack would propagate into the PPE/SEBS domain, and the stresses dissipated.

Figure 19. Toughening mechanism. Figure 19. Toughening mechanism.

Performance enhancementsPerformance enhancements from the from PPE-PHE the PPE-PHE block block copolymers copolymers were were noted noted in tensile in tensile properties. properties. Tensile modulus and strengthFigure increase 19. Tougheningd with the mechanism. addition of PHE and ABC-36 as shown Tensile modulusin Figures and strength20 and 21, respectively. increased The with increases the were addition greater when of ABC-36 PHE was and used ABC-36 as a as shown in Figures 20 and 21compatibilizer., respectively.Performance While enhancements Thethe PHE increases gave from properties the were PPE-PHE better greater than block the when uncompatibilizedcopolymers ABC-36 were was PBT/PPE/SEBS noted used in tensile as a compatibilizer. blend,properties. the property Tensile enhancementsmodulus and strengthwere less increase than thosed with from the the addition ABC-36 ofcomposition. PHE and ABC-36 This effect as shownof While the PHE gavePHEin Figures may properties be 20due and to weak 21, better hydrogenrespectively. than bonding theThe with uncompatibilizedincrea theses PPE were dispersed greater phase. when PBT/PPE/SEBS Looking ABC-36 at uniaxial was used stress blend, as a the property enhancements wereincompatibilizer. Figure less 22, the than ABC-36While those thematerial PHE from hadgave significantly the properties ABC-36 higher better composition.elongation than the atuncompatibilized break compared This effect toPBT/PPE/SEBS the blend of PHE may be due onlyblend, or thewith property PHE containing enhancements blend. were less than those from the ABC-36 composition. This effect of to weak hydrogenPHE bondingmay be due to with weak hydrogen the PPE bonding dispersed with the phase.PPE dispersed Looking phase. Looking at uniaxial at uniaxial stress stress in Figure 22, the ABC-36 materialin Figure had 22, the significantly ABC-36 material higher had significantly elongation higher atelongation break at compared break compared to theto the blend blend only or with PHE containingonly blend. or with PHE containing blend.

Figure 20. Effect of ABC on tensile modulus.

Polymers 2017, 9, 433 Figure 20. Effect of ABC on tensile modulus. 12 of 25 Polymers 2017, 9, 433 Figure 20. Effect of ABC on tensile modulus. 12 of 25

Figure 21. Effect of ABC on tensile strength. Figure 21.FigureEffect 21. Effect ofABC of ABC onon tensile tensile strength. strength.

Figure 22. Effect of ABC on elongation at break. Figure 22.FigureEffect 22. Effect of ABC of ABC on on elongation at break. at break. 3.2.2. Interface in Composites—Glass Reinforced Polystyrene 3.2.2. Interface in Composites—Glass Reinforced Polystyrene The addition of reinforcing fillers and glass fibers to polymers can produce significant The addition of reinforcing fillers and glass fibers to polymers can produce significant improvements in mechanical properties. The reinforcing additives can have geometries such as improvements in mechanical properties. The reinforcing additives can have geometries such as fibers, flakes, spheres, and particulates. Reinforced polymers would consist of two or more fibers, flakes, spheres, and particulates. Reinforced polymers would consist of two or more components and two or more phases. Ideally, any applied stresses would be transmitted from the components and two or more phases. Ideally, any applied stresses would be transmitted from the continuous polymer matrix to the reinforcing material. The efficient transfer of stress from the matrix continuous polymer matrix to the reinforcing material. The efficient transfer of stress from the matrix to the dispersed reinforcing material can increase the system ability to absorb energy and translate to to the dispersed reinforcing material can increase the system ability to absorb energy and translate to increased mechanical properties. Clearly, interphase attraction between reinforcing material and increased mechanical properties. Clearly, interphase attraction between reinforcing material and polymer matrix is of paramount importance. Indeed, the mechanical properties of fiber-reinforced polymer matrix is of paramount importance. Indeed, the mechanical properties of fiber-reinforced composites largely depend on the interphase between the reinforcement and the matrix. composites largely depend on the interphase between the reinforcement and the matrix. Some chemical compounds that are used to increase the polymer matrix attraction to a filler Some chemical compounds that are used to increase the polymer matrix attraction to a filler surface are called coupling agents. The most common coupling agents are organo-silanes [42]. surface are called coupling agents. The most common coupling agents are organo-silanes [42]. Hydrogen bonding is an important mechanism to enhance the polymer–filler interface [43]. Hydrogen bonding is an important mechanism to enhance the polymer–filler interface [43]. Optimizing performance via good adhesion between the matrix and fiber is a challenge in glass Optimizing performance via good adhesion between the matrix and fiber is a challenge in glass fiber reinforced polystyrene. In general, glass fiber, GF, contains a coupling agent on the surface to fiber reinforced polystyrene. In general, glass fiber, GF, contains a coupling agent on the surface to facilitate fiber-matrix attraction. One of the most common agents is γ-amino-propyl-silane. However, facilitate fiber-matrix attraction. One of the most common agents is γ-amino-propyl-silane. However, in non-polar polymers such as polystyrene there are no opportunities for hydrogen bonding or other in non-polar polymers such as polystyrene there are no opportunities for hydrogen bonding or other interactions with GF. interactions with GF. The amphiphilic PPE-PHE block copolymers were evaluated as additives for increasing the The amphiphilic PPE-PHE block copolymers were evaluated as additives for increasing the interphase attraction between fiber and PS. The PPE segments polystyrene-philic and the PHE interphase attraction between fiber and PS. The PPE segments polystyrene-philic and the PHE segments contain hydroxyl groups to facilitate hydrogen bonding. segments contain hydroxyl groups to facilitate hydrogen bonding.

Polymers 2017, 9, 433 12 of 24

3.2.2. Interface in Composites—Glass Reinforced Polystyrene The addition of reinforcing fillers and glass fibers to polymers can produce significant improvements in mechanical properties. The reinforcing additives can have geometries such as fibers, flakes, spheres, and particulates. Reinforced polymers would consist of two or more components and two or more phases. Ideally, any applied stresses would be transmitted from the continuous polymer matrix to the reinforcing material. The efficient transfer of stress from the matrix to the dispersed reinforcing material can increase the system ability to absorb energy and translate to increased mechanical properties. Clearly, interphase attraction between reinforcing material and polymer matrix is of paramount importance. Indeed, the mechanical properties of fiber-reinforced composites largely depend on the interphase between the reinforcement and the matrix. Some chemical compounds that are used to increase the polymer matrix attraction to a filler surface are called coupling agents. The most common coupling agents are organo-silanes [42]. Hydrogen bonding is an important mechanism to enhance the polymer–filler interface [43]. Optimizing performance via good adhesion between the matrix and fiber is a challenge in glass fiber reinforced polystyrene. In general, glass fiber, GF, contains a coupling agent on the surface to facilitate fiber-matrix attraction. One of the most common agents is γ-amino-propyl-silane. However, in non-polar polymers such as polystyrene there are no opportunities for hydrogen bonding or other interactions with GF. The amphiphilic PPE-PHE block copolymers were evaluated as additives for increasing the interphasePolymers 2017 attraction, 9, 433 between fiber and PS. The PPE segments polystyrene-philic and the PHE segments13 of 25 contain hydroxyl groups to facilitate hydrogen bonding. The resin–fiberresin–fiber interface on fractured surfaces of polystyrene containingcontaining 20% glass fiberfiber was examined by microscopy. The The effects effects of of 0% and 5% ABC-36 are compared by scanningscanning electron microscope (SEM) in Figure 2323.. In Figure 2323a,a, there is no indication of any resin interaction with the GF. There is no no PS PS adhering adhering to to GF GF and and there there is issepara separationtion of ofthe the GF GF from from the the PS PSat the at thebase base of the of GF. the GF.On Onthe theother other hand, hand, the theSEM SEM in inFigure Figure 23b 23 bfor for po polystyrenelystyrene containing containing 5 5wt wt % % ABC-36 ABC-36 shows resin adhering to the GF and at the base of the fiberfiber therethere is good resin–fiberresin–fiber adhesion.adhesion. These SEM results suggest thatthat the the ABC ABC increased increased the the interfacial interfacial adhesion adhesion between between the GF the and GF the and PS. Thethe PHEPS. The segments PHE cansegments hydrogen can hydrogen bond to the bond GF surfaceto the GF and surface the PPE and segments the PPE aresegments soluble are in thesoluble PS. in the PS.

(a) (b)

Figure 23. Scanning electron microscope (SEM)(SEM) images of GF-PS interfaces: ( a)) no interfacial agent; and (b) ABC-36 as interfacial agent.agent.

This effect of ABC on interfacial adhesion is depicted in Figure 24. In the PS–GF blend there is This effect of ABC on interfacial adhesion is depicted in Figure 24. In the PS–GF blend there is no no interaction between the non-polar PS and the polar moieties on the GF surface (Figure 24a). On interaction between the non-polar PS and the polar moieties on the GF surface (Figure 24a). On the the other hand, with ABC, the PHE segment would have greater affinity of the polar moieties on the other hand, with ABC, the PHE segment would have greater affinity of the polar moieties on the GF GF and could hydrogen bond with the amino-silanes on the surface (Figure 24b). In addition, the PPE and could hydrogen bond with the amino-silanes on the surface (Figure 24b). In addition, the PPE segments would be soluble in the PS. This increase adhesion at the interface translates to increase in segments would be soluble in the PS. This increase adhesion at the interface translates to increase properties. in properties.

(a) (b)

Figure 24. Depiction of PS-GF Interfaces: (a) no interaction and no adhesion; and (b) ABC at interface and good adhesion.

In control blends, PS/GF and PS/GF with 5 wt % PHE, the NIs were low. However, with 5 wt % ABC-36, the NIs were substantially higher, as shown in Figure 25. This suggests that the good resin– fiber adhesion from utilizing the ABC can better transfer any applied stresses from the PS phase to the GF.

Polymers 2017, 9, 433 13 of 25

The resin–fiber interface on fractured surfaces of polystyrene containing 20% glass fiber was examined by microscopy. The effects of 0% and 5% ABC-36 are compared by scanning electron microscope (SEM) in Figure 23. In Figure 23a, there is no indication of any resin interaction with the GF. There is no PS adhering to GF and there is separation of the GF from the PS at the base of the GF. On the other hand, the SEM in Figure 23b for polystyrene containing 5 wt % ABC-36 shows resin adhering to the GF and at the base of the fiber there is good resin–fiber adhesion. These SEM results suggest that the ABC increased the interfacial adhesion between the GF and the PS. The PHE segments can hydrogen bond to the GF surface and the PPE segments are soluble in the PS.

(a) (b)

Figure 23. Scanning electron microscope (SEM) images of GF-PS interfaces: (a) no interfacial agent; and (b) ABC-36 as interfacial agent.

This effect of ABC on interfacial adhesion is depicted in Figure 24. In the PS–GF blend there is no interaction between the non-polar PS and the polar moieties on the GF surface (Figure 24a). On the other hand, with ABC, the PHE segment would have greater affinity of the polar moieties on the GF and could hydrogen bond with the amino-silanes on the surface (Figure 24b). In addition, the PPE Polymers 2017, 9, 433 13 of 24 segments would be soluble in the PS. This increase adhesion at the interface translates to increase in properties.

(a) (b)

Figure 24. Depiction of PS-GF Interfaces: (a) no interaction and no adhesion; and (b) ABC at interface Figure 24.andDepiction good adhesion. of PS-GF Interfaces: (a) no interaction and no adhesion; and (b) ABC at interface and good adhesion. In control blends, PS/GF and PS/GF with 5 wt % PHE, the NIs were low. However, with 5 wt % ABC-36, the NIs were substantially higher, as shown in Figure 25. This suggests that the good resin– In controlfiber adhesion blends, from PS/GF utilizing and the PS/GF ABC can with better 5 wt tran %sfer PHE, any theapplied NIs stresses were low.from the However, PS phase withto 5 wt % ABC-36, thethe GF. NIs were substantially higher, as shown in Figure 25. This suggests that the good resin–fiber adhesion from utilizing the ABC can better transfer any applied stresses from the PS phase to the GF. Polymers 2017, 9, 433 14 of 25 Polymers 2017, 9, 433 14 of 25

FigureFigure 25. 25.Effect Effect of of ABCABC on on NI. NI. Figure 25. Effect of ABC on NI. The effect of the molecular weight of the PPE-M segments in the ABC on impact strength appears The effect of the molecular weight of the PPE-M segments in the ABC on impact strength appears in FigureThe effect 26. The of the ABC molecular contained weight 48 wt of % the PPE-M PPE-M se gmentssegments and in the MnABC ranged on impact from strength 1150 to appears2750. All in Figure 26inblends Figure. The contained 26. ABC The containedABC 5 wt contained % ABC 48 and 48 wt 20wt %wt% PPE-M PPE-M% GF. The segments segments impact and strength the and Mn increased the ranged Mn fromwith ranged 1150increasing to from 2750. length 1150All to 2750. All blendsblendsof contained the contained PPE segment. 5 wt5 wt % % This ABCABC suggests and and 20 20wt that % wt GF.the % Thehigh GF. imer Thepact molecular strength impact weight increased strength segments with increased increasing gives increased with length increasing length of theofadhesion the PPE PPE segment. between segment. ABC ThisThis and suggests PS. The that amount that the the highof higherPHEer molecular segment molecular andweight the weight segmentssecondary segments givesalcohol increased levels gives is increased adhesionessentially between unchanged. ABC and PS. The amount of PHE segment and the secondary alcohol levels is adhesion between ABC and PS. The amount of PHE segment and the secondary alcohol levels is essentially unchanged. essentially unchanged.

Figure 26. NI versus Mn of PPE-M segments. Figure 26. NI versus Mn of PPE-M segments. Figure 26. NI versus Mn of PPE-M segments. The effects on PHE and ABCs on the flexural properties appear in Figures 27 and 28. The ABC The effectsblendsThe onare effects PHEmore on effective and PHE ABCs and than ABCs onPHE on the in the enhancin flexural flexuralg the properties FM and appear FS appear above in Figuresthe in values Figures 27 forand PS/GF. 2728. andThe ABC 28. The ABC blends areblends more are effective more effective than PHEthan PHE in enhancing in enhancing thethe FM and and FS FSabove above the values the values for PS/GF. for PS/GF.

Figure 27. Flexural modulus versus ABC. Figure 27. Flexural modulus versus ABC.

Polymers 2017, 9, 433 14 of 25

Figure 25. Effect of ABC on NI.

The effect of the molecular weight of the PPE-M segments in the ABC on impact strength appears in Figure 26. The ABC contained 48 wt % PPE-M segments and the Mn ranged from 1150 to 2750. All blends contained 5 wt % ABC and 20 wt % GF. The impact strength increased with increasing length of the PPE segment. This suggests that the higher molecular weight segments gives increased adhesion between ABC and PS. The amount of PHE segment and the secondary alcohol levels is essentially unchanged.

Figure 26. NI versus Mn of PPE-M segments.

Polymers 2017, 9, 433The effects on PHE and ABCs on the flexural properties appear in Figures 27 and 28. The ABC 14 of 24 blends are more effective than PHE in enhancing the FM and FS above the values for PS/GF.

Polymers 2017, 9, 433 15 of 25 Polymers 2017, 9, 433 FigureFigure 27. Flexural27. Flexural modulus modulus versus versus ABC. ABC. 15 of 25

Figure 28. Flexural strength versus ABC. FigureFigureFigure 28. 28. 28.Flexural Flexural Flexural strength strength versus versus versus ABC. ABC. ABC. As shown with NI, the higher is the molecular weight of the PPE-M segments, the greater is the AsAs shown shown with with NI, NI, the the higher higher is is the the molecular molecular weight weight of of the the PP PPE-ME-M segments, segments, the the greater greater is is the the increase in properties. The effect of PPE Mn on FM and FS are shown in Figures 29 and 30, As shownincreaseincrease with inin properties.properties. NI, the higher TheThe effecteffect is the ofof molecularPPEPPE MnMn onon weightFMFM andand ofFSFS the areare PPE-Mshownshown inin segments, FiguresFigures 2929 the andand greater 30,30, is the respectively. increase inrespectively.respectively. properties. The effect of PPE Mn on FM and FS are shown in Figures 29 and 30, respectively.

FigureFigure 29. Flexural 29. Flexural modulus modulus versusversus Mn Mn of ofPPE-M PPE-M Segments. Segments. FigureFigure 29. 29. Flexural Flexural modulus modulus versus versus Mn Mn of of PPE-M PPE-M Segments. Segments.

FigureFigure 30. Flexural 30. Flexural strength strength versusversus Mn Mn of ofPPE-M PPE-M segments. segments. FigureFigure 30. 30. Flexural Flexural strength strength versus versus Mn Mn of of PPE-M PPE-M segments. segments. TS are higher with ABC-36, as shown in Figure 31. These enhanced physical properties suggest TS are higherTSTS are are with higher higher ABC-36, with with ABC-36, ABC-36, as shown as as shown shown in in in Figure Figure Figure 31. 3131. .These These These enhanced enhanced enhanced physical physical physical properties properties properties suggest suggest suggest that the ABCs are effective in increasing the interfacial adhesion between the PS and GF. that the ABCsthat the are ABCs effective are effective in increasing in increasing the the interfacial interfacial adhesion between between the PS the and PS GF. and GF.

Polymers 2017, 9, 433 16 of 25 PolymersPolymers2017 2017, 9, ,9 433, 433 1516 of of 24 25

Figure 31. Tensile strength versus ABC. Figure 31. Tensile strength versus ABC. Figure 31. Tensile strength versus ABC. Values for HDT results appear in Figure 32. The HDT was much higher with 5 wt % ABC-36. ThisValues may be for due HDT in part results to the appear Tg of in121 Figure °C for 32 ABC-36. The HDT compared was much to a Tg higher of 100 with °C for 5 wtPS. % The ABC-36. higher Values for HDT results appear in ◦Figure 32. The HDT was much higher ◦with 5 wt % ABC-36. ThisThisHDT may may is in be be line due due with in in part partthe to higherto the the Tg Tgmodulus of of 121 121 C°Cof for thefor ABC-36 ABC-36ABC based compared compared blends to toand a a Tg Tgthe of of report 100 100 °CC that for for PS.there PS. The The is highera higher direct HDTHDTcorrelation is is in in line line of with thewith HDT the the higher higherof amorphous modulus modulus polymers of of the the ABC ABC with based based their blends blends modulus and and thebehavior the report report of that that the there theresample is is a a[44,45]. direct direct correlationThe HDT for of the5 wt HDT % PHE of amorphouswas lower than polymers for PS/GF. with This their may modulus be related behavior in part of to the the sample lower [Tg44 ,of45 91]. correlation of the HDT of amorphous polymers with their modulus behavior of the sample [44,45].◦ TheThe°C HDTfor HDT the for forPHE. 5 wt5 wt % % PHE PHE was was lower lower than than for for PS/GF. PS/GF. This This may may be relatedbe related in part in part to the to lowerthe lowerTg of Tg 91 of C91 for°C thefor PHE.the PHE.

Figure 32. HDT of PS/GF Blends. Figure 32. HDT of PS/GF Blends. 3.3. Thermoplastic Polyurethanes Figure 32. HDT of PS/GF Blends. 3.3. Thermoplastic Polyurethanes TPUs are versatile polymers with many useful properties. These inherently flexible polymers 3.3. ThermoplasticTPUs are versatile Polyurethanes polymers with many useful properties. These inherently flexible polymers are renowned for high tensile elongation, resistance to oil, grease, and certain chemicals and solvents. are renowned for high tensile elongation, resistance to oil, grease, and certain chemicals and solvents. TheseTPUs characteristics are versatile make polymers TPU extremely with many popular useful properties. across a range These of inherently markets andflexible applications. polymers These characteristics make TPU extremely popular across a range of markets and applications. However,are renowned features for high also tensile include elongation, limited service resistance temperature, to oil, grease, high and moisture certain chemicals absorption, and and solvents. poor However, features also include limited service temperature, high moisture absorption, and poor resistanceThese characteristics to burning. make Clearly, TPU the extremely features ofpopula PPE-Mr across and TPUs a range are complementaryof markets and andapplications. suggest resistance to burning. Clearly, the features of PPE-M and TPUs are complementary and suggest an anHowever, opportunity features to enhancealso include performance limited service of TPUs temperature, with PPE-TPU high amphiphilicmoisture absorption, block copolymers. and poor opportunity to enhance performance of TPUs with PPE-TPU amphiphilic block copolymers. Thus, Thus,resistance PPE-M to burning. was used Clearly, as a hydrophobic the features polyolof PPE-M to prepareand TPUs TPU are amphiphiliccomplementary block and copolymers suggest an PPE-M was used as a hydrophobic polyol to prepare TPU amphiphilic block copolymers where the whereopportunity the content to enhance of the PPE performance segments of were TPUs 0, 7.65, with 15.3, PPE-TPU and 23 amphiphilic wt %. block copolymers. Thus, content of the PPE segments were 0, 7.65, 15.3, and 23 wt %. PPE-MWater was absorption used as a hydrophobic in polymers ispolyol known to prep to haveare TPU adverse amphiphilic effects on block dimensional copolymers stability, where Tg,the Water absorption in polymers is known to have adverse effects on dimensional stability, Tg, mechanicalcontent of the properties, PPE segments and dielectric were 0, 7.65, properties. 15.3, and Urethanes 23 wt %. can form hydrogen bonds to substrates mechanical properties, and dielectric properties. Urethanes can form hydrogen bonds to substrates throughWater the polarabsorption urethane in grouppolymers [46 ,47is ].known While to the have urethane adverse moiety effects can on hydrogen dimensional bond tostability, substrates Tg, through the polar urethane group [46,47]. While the urethane moiety can hydrogen bond to tomechanical increase adhesion, properties, it can and also dielectric strongly properties. hydrogen Urethanes bond with can water. form However, hydrogen PPE bonds does to not substrates contain substrates to increase adhesion, it can also strongly hydrogen bond with water. However, PPE does polarthrough groups, the whichpolar urethane would strongly group hydrogen[46,47]. While bond the to water, urethane and, moiety correspondingly, can hydrogen has very bond low to not contain polar groups, which would strongly hydrogen bond to water, and, correspondingly, has watersubstrates absorption. to increase The adhesion, effect of PPE-Mit can also on moisturestrongly hydrogen uptake in bond TPUs with was water. examined However, by the PPE weight does very low water absorption. The effect of PPE-M on moisture uptake in TPUs was examined by the changenot contain after exposurepolar groups, to 100% which relative would humidity strongly (RH) hydr atogen 50 ◦ Cbond for sevento water, days and, and correspondingly, immersion in water has weight change after exposure to 100% relative humidity (RH) at 50 °C for seven days and immersion atvery ambient low water temperature absorption. for three The days.effect Asof PPE-M shown inon Figuresmoisture 33 uptakeand 34 ,in the TPUs TPU was without examined any PPE-M by the weight change after exposure to 100% relative humidity (RH) at 50 °C for seven days and immersion

Polymers 2017, 9, 433 17 of 25 Polymers 2017, 9, 433 17 of 25 Polymers 2017, 9, 433 17 of 25 Polymersin water2017 at ,ambient9, 433 temperature for three days. As shown in Figures 33 and 34, the TPU without16 ofany 24 in water at ambient temperature for three days. As shown in Figures 33 and 34, the TPU without any inPPE-M water absorbs at ambient high temperature levels of water. for three However, days. As with shown increasing in Figures amounts 33 and 34,of thePPE-M, TPU withoutthere was any a PPE-M absorbs high levels of water. However, with increasing amounts of PPE-M, there was a PPE-Msignificant absorbs decrease high in levels water ofabsorption. water. However, with increasing amounts of PPE-M, there was a significant decrease in water absorption. significantabsorbs high decrease levels in of water water. absorption. However, with increasing amounts of PPE-M, there was a significant decrease in water absorption.

Figure 33. Water uptake after three-day immersion in water. Figure 33. Water uptake after three-day immersion in water. FigureFigure 33. 33. WaterWater uptake uptake after after three-day three-day immersion in water.

Figure 34. Moisture uptake at 50 ◦°C and 100% RH. Figure 34. Moisture uptake at 50 °CC and 100% RH. Figure 34. Moisture uptake at 50 °C and 100% RH. Water contact angles are considered as a measure of hydrophobicity of a surface. In general, if Water contact angles are considered as a measure of hydrophobicity of a surface. In general, if the waterWater contact contact angle angles angles is are arelarger considered considered than 90°, asas the a a measure measuresurface isof of consideredhydrophobicity hydrophobicity hydrophobic of of a asurface. surface. and, In if In general,the general, water if the water contact angle is larger than 90°,◦ the surface is considered hydrophobic and, if the water thecontactif the water water angle contact contact is smaller angle angle isthan islarger larger 90°, thanthe than surface 90°, 90 the, the is su co surfacerfacensidered is is considered considered hydrophilic hydrophobic hydrophobic [48,49]. As and,shown and, if if the thein Figure water contact angle is smaller than 90°,◦ the surface is considered hydrophilic [48,49]. As shown in Figure contact35,contact the hydrophobicity angle isis smallersmaller ofthanthan the 90 90°,TPUs, thethe increased surface surface is is with considered considered increasing hydrophilic hydrophilic levels of [48 PPE-M.[48,49].,49]. As Indeed,As shown shown around in Figurein Figure 15.3 35, 35, the hydrophobicity of the TPUs increased with increasing levels of PPE-M. Indeed, around 15.3 35,wtthe %the hydrophobicity PPE-M hydrophobicity the contact of the of angle TPUsthe TPUs is increased 92°. increased with with increasing increasing levels levels of PPE-M. of PPE-M. Indeed, Indeed, around around 15.3 wt15.3 % wt % PPE-M the contact angle◦ is 92°. wtPPE-M % PPE-M the contact the contact angle angle is 92 .is 92°.

Figure 35. Contact angles of versus PPE-M content. Figure 35. Contact angles of versus PPE-M content. Figure 35. Contact angles of versus PPE-M content. Figure 35. Contact angles of versus PPE-M content. Other hydrophobic diols and technologies have been used to prepare hydrophobic TPUs. These include the use of polybutadiene diols [50,51], α,ω-dihydroxypoly(dimethylsiloxane) [52] and

Polymers 2017, 9, 433 18 of 25 Polymers 2017, 9, 433 18 of 25 PolymersOther2017 hydrophobic, 9, 433 diols and technologies have been used to prepare hydrophobic TPUs. These17 of 24 Other hydrophobic diols and technologies have been used to prepare hydrophobic TPUs. These include the use of polybutadiene diols [50,51], α,ω-dihydroxypoly(dimethylsiloxane) [52] and include the use of polybutadiene diols [50,51], α,ω-dihydroxypoly(dimethylsiloxane) [52] and fluorinated macrodiols [53]. In addition, plasma treatment of the surface of TPUs has been used to fluorinatedfluorinated macrodiols macrodiols [53]. [53]. In In addition, addition, plasma plasma tr treatmenteatment of of the the surface surface of of TPUs TPUs has has been been used used to to increase the hydrophobicity [54]. However, these hydrophobic diols lack the engineering features of increaseincrease the the hydrophobicity hydrophobicity [54]. [54]. However, However, these these hy hydrophobicdrophobic diols diols lack lack the the engineering engineering features features of of PPE-M. Butadiene segments are prone to oxidation and, in general, siloxanes have poor tear, abrasion PPE-M.PPE-M. Butadiene Butadiene segments segments are are prone prone to to oxidation oxidation and, and, in in general, general, siloxanes siloxanes have have poor poor tear, tear, abrasion abrasion and tensile strength. andand tensile tensile strength. strength. Abrasion resistance is a quantifiable property according to industry-standard Taber abrasion AbrasionAbrasion resistance resistance is is a a quantifiable quantifiable property property according according to to industry-standard industry-standard Taber Taber abrasion abrasion testing. Polyurethanes have long been recognized for their ability to resist wear in challenging testing.testing. Polyurethanes Polyurethanes have have long long been been recognized recognized for for their their ability ability to to resist resist wear wear in in challenging challenging applications. The effect of PPE-M on accelerated wear testing of TPUs was performed. The weight applications.applications. The The effect effect of of PPE-M PPE-M on on accelerated accelerated wear wear testing testing of of TPUs TPUs was was performed. performed. The The weight weight loss data using a Taber Rotary Abrader appear in Figure 36. The wear resistance of the TPUs was lossloss data data using using a a Taber Taber Rotary Rotary Abrader Abrader appear appear in in Figure Figure 36.36. The The wear wear resistance resistance of of the the TPUs TPUs was was significantly increased with higher levels of PPE-M. significantlysignificantly increased increased with with higher higher levels levels of of PPE-M. PPE-M.

Figure 36. Wear resistance. FigureFigure 36. 36. WearWear resistance. resistance. The tear strengths of the TPUs were measured according to specification ASTM D624—Die C. The tear strengths of the TPUs were measured according to specification ASTM D624—Die C. The testThe measures tear strengths the resistance of the TPUs in a were material measured to the according formation to of specification a tear (tearASTM initiation) D624—Die and the C . The test measures the resistance in a material to the formation of a tear (tear initiation) and the resistanceThe test measuresto the expansion the resistance of a tear in (tear a material propagat toion). the The formation tear strengths of a tear were (tear significantly initiation) andgreater the resistance to the expansion of a tear (tear propagation). The tear strengths were significantly greater withresistance increased to the levels expansion of PPE-M, of a tearas shown (tear propagation). in Figure 37. ThePPEs tear engineering strengths werefeatures significantly of strength greater and with increased levels of PPE-M, as shown in Figure 37. PPEs engineering features of strength and toughnesswith increased contribute levels to of the PPE-M, enhancements as shown in in tear Figure strength 37. PPEs and wear engineering resistance. features of strength and toughness contribute to the enhancements in tear strength and wear resistance. toughness contribute to the enhancements in tear strength and wear resistance.

Figure 37. Tear resistance. Figure 37. Tear resistance. Figure 37. Tear resistance. AtAt ambient ambient temperatures, temperatures, all all of of the the TPUs TPUs exhibi exhibitedted elongations elongations greater greater than than 500%. 500%. At At elevated elevated At ambient temperatures, all of the TPUs exhibited elongations greater than 500%. At elevated temperatures,temperatures, the the elongations elongations decreased. decreased. The The PP PPE-ME-M based based TPUs TPUs exhibited exhibited greater greater retention retention of of temperatures, the elongations decreased.◦ The PPE-M ◦based TPUs exhibited greater retention of elongationelongation going going from from 50 50 to to 75 75 °C.C. In In addition, addition, at at 70 70 °C,C, the the TPU TPU with with no no PPE-M PPE-M was was too too soft soft for for elongation going from 50 to 75 °C. In addition, at 70 °C, the TPU with no PPE-M was too soft for testing.testing. The The results results appear appear in in Figure Figure 38.38 .Increased Increased levels levels of of PPE PPE and and its its high high thermal thermal performance performance testing. The results appear in Figure 38. Increased levels of PPE and its high thermal performance featurefeature result result in in enhanced enhanced performance performance at at elevated elevated temperatures. temperatures. feature result in enhanced performance at elevated temperatures.

Polymers 2017, 9, 433 19 of 25 Polymers 2017,, 9,, 433433 1819 of 2425

Figure 38. Elongation at elevated temperatures. Figure 38. Elongation at elevated temperatures. Figure 38. Elongation at elevated temperatures. The aliphatic ether polyols are susceptible to oxidation and are subject to auto-oxidation. The basicThe mechanism aliphaticaliphatic etherforether auto-oxidation polyols polyols are are susceptible susceptibleof polyethers to oxidationto followsoxidation and the and arescheme subjectare subject reported to auto-oxidation. to auto-oxidation.by Bolland The and basic TheGee mechanismbasic[55]. Themechanism degradation for auto-oxidation for auto-oxidation is initiated of by polyethers oxygenof polyethers molecu follows followsles the which scheme the formscheme reported peroxy reported byradicals Bolland by Bolland(P–O–O•) and Geeand on [Gee 55the]. • The[55].polyether degradationThe degradation [56]. In isthe initiated ispropagation initiated by oxygenby step, oxygen the molecules peroxymolecu lesradical which which abstracts form form peroxy peroxy a hydrogen radicals radicals from(P–O–O (P–O–O•) a polyether) onon thethe to polyetherform a hydroperoxide [[56].56]. In the propagation (P–O–O• + RH step, → the P–O–OH peroxy + radical R•). The abstracts hydroperoxide a hydrogen will from undergo a polyetherpolyether thermally to • → • forminduced a hydroperoxide degradative reactions. (P–O–O(P–O–O• The ++ RH alkyl → P–O–OHradical (R•) + R•). R will). The The react hydroperoxide hydroperoxide with oxygen to will from undergo a hydroperoxide thermally • induced(R–O–O•) degradative and continue reactions. the auto-oxidation The alkyl radical reactions. (R•) (R ) will react with oxygen to from a hydroperoxide • (R–O–O(R–O–O•)PPE) has andand a continuecontinuehighly aromatic thethe auto-oxidationauto-oxidation backbone with reactions.reactions. no aliphatic ether groups and which does not readily undergoPPE hasthermo-oxidative a highly aromatic reactions. backbonebackbo Inne general, with no PP aliphaticE based ether thermoplastics groups and are which used does in applications not readily undergoexposed thermo-oxidativeto elevated temperatures reactions. [1,5]. In general, PP PPEE based thermoplastics are used in applicationsapplications exposedThe to enhancement elevated temperatures of thermo-oxidative [[1,5].1,5]. stability versus the PPE levels was measured by heat agingThe test enhancementenhancement parts at 100 of of thermo-oxidative °Cthermo-oxidative for seven days stability stability and versusthen versus themeasuring the PPE PPE levels tensilelevels was measuredwasproperties measured by at heat ambientby aging heat ◦ testagingtemperature. parts test at parts 100 The Catsample for100 seven °Cwithout for days seven PPE-M and thendays had measuring anddeterior thenated tensilemeasuring and became properties tensile too at softproperties ambient for testing. temperature.at ambientSamples Thetemperature.with sample PPE-M without exhibitedThe sample PPE-M much without had greater deteriorated PPE-M retention had anddeteriorof prop becameertiesated too andafter soft became heat for aging, testing. too soft as Samples shown for testing. in with Figure Samples PPE-M 39. exhibitedwith PPE-M much exhibited greater much retention greater of properties retention of after prop heaterties aging, after as heat shown aging, in Figureas shown 39. in Figure 39.

Figure 39. Effect of PPE-M on heat aging at 100 ◦C. Figure 39. Effect of PPE-M on heat aging at 100 °C. Figure 39. Effect of PPE-M on heat aging at 100 °C. AA keykey featurefeature ofof PPEPPE isis itsits veryvery lowlow dielectricdielectric properties.properties. TheThe useuse ofof PPE-MPPE-M inin TPUsTPUs impartsimparts greatergreaterA key electricelectric feature insulatinginsulating of PPE properties.properti is its veryes. Indeed,Indeed,low dielectric thethe dielectricdielectric properties. constantconstant The (Dk (Dkuse ororofrelative relativePPE-M permittivity)permittivity)in TPUs imparts andand lossgreaterloss tangenttangent electric (Df(Df insulating oror dissipationdissipation properti factor)factor)es. Indeed, atat 11 MHzMHz the decreaseddecreased dielectric withwithconstant increasedincreased (Dk or PPE-MPPE-M relative levels,levels, permittivity) asas shownshown and inin FigureslossFigures tangent 4040 andand (Df 4141. or. dissipation factor) at 1 MHz decreased with increased PPE-M levels, as shown in Figures 40 and 41.

PolymersPolymers 20172017,, 99,, 433433 1920 ofof 2425 Polymers 2017, 9, 433 20 of 25

Figure 40.40. Dielectric constant.

Figure 41.41. Loss tangent.

Chemical resistance of TPUs containing PPE-M improved in both polar and non-polar solvents Chemical resistance of TPUs containing PPE-M improved in both polar and non-polarnon-polar solvents as well as in oil and acidic and basic solutions. The weight gain after three day of immersion in the as well as in oiloil andand acidicacidic andand basicbasic solutions.solutions. The weight gain after three day of immersionimmersion in the chemicals at ambient temperatures, decreased with an increase of PPE-M levels in TPUs. Data for chemicals at ambient temperatures, decreased with an increase of PPE-MPPE-M levelslevels inin TPUs.TPUs. Data for TPUs with 0% and 23% PPE-M are summarized in Table 5. TPUs with 0%0% andand 23%23% PPE-MPPE-M areare summarizedsummarized inin TableTable5 .5.

Table 5. Weight increase (%)(%) afterafter immersionimmersion inin chemicalschemicals forfor threethree days.days.

PPE-M Content, wt % Chemical PPE-M Content, wt % Chemical 023 0 23 Toluene 290 150 TolueneOil 2900.34 0.18 150 HydrochloricOil acid, pH 1 0.3484 0.1819 SodiumHydrochloric hydroxide, acid, pH 113 8470 1929 Sodium hydroxide, pH 13 70 29 Thermal decomposition and combustion are an important area in some polyurethane applications.Thermal In decomposition general, polyurethanes and combustion are very are ancombustible important areaplastics in some [57]. polyurethaneThe thermal applications.degradation Inof polyether-urethanes general, polyurethanes is complex are very since combustible the structure plastics contains [57]. Theboth thermal polyether degradation and urethane of polyether-segments. urethanesThe thermal is complexdecomposition since the involves structure the contains urethane both linkage polyether undergoing and urethane an O-acyl segments. fission The generally thermal decompositionbelow 300 °C to involves generate the the urethane free isocyanate linkage undergoingand alcohol an[58]. O-acyl Moreover, fission it generally has been below estimated 300 ◦ Cthat to generatethe thermal the degradation free isocyanate of some and polyurethane alcohol [58]. products Moreover, may it begin has been as low estimated as about that 150 the°C to thermal 180 °C degradation[59]. In addition of someto thermos-oxidative polyurethane products degradation, may aliphatic begin as polyether low as aboutpolyols 150 are◦ proneC to 180 to thermal◦C[59]. Indegradation addition towhere thermos-oxidative the degradation degradation, is initiated by aliphatic random polyether scission of polyols both C‒ areO and prone C‒C to bonds thermal in degradationthe polymer chains where [60]. the degradation is initiated by random scission of both C-O and C-C bonds in theOn polymer the other chains hand, [60 PPE]. has an aryl ether backbone with much greater thermal stability. Studies on theOn thermal the other degradation hand, PPE of has PPE an arylhave ether shown backbone that the with thermal much degradation greater thermal occurs stability. in two Studiessteps [61– on the63]. thermalThe first degradation step in the ofdegradation PPE have shownoccurs thatbetween the thermal 430 and degradation 500 °C where occurs the inpolymer two steps undergoes [61–63]. thermal Fries-type rearrangements of the polymer chain [64]. Hence, the methyl aryl ethers undergo

Polymers 2017, 9, 433 20 of 24

PolymersPolymers 2017 2017, ,9 9, ,433 433 2121 of of 25 25 The first step in the degradation occurs between 430 and 500 ◦C where the polymer undergoes thermal thermalFries-typethermal rearrangementrearrangement rearrangements inin of thethe the formationformation polymer chain ofof benzylbenzyl [64]. Hence, phenols.phenols. the The methylThe secondsecond aryl ethers stepstep occurs undergooccurs atat thermal higherhigher temperaturesrearrangementtemperatures where where in the the the formation char-forming char-forming of benzyl process process phenols. results results Thein in the the second formation formation step occursof of a a black, black, at higher highly highly temperatures cross-linked cross-linked residuewhereresidue the and and char-forming the the evolution evolution process of of phenolic phenolic results products, inproducts, the formation an andd water. water. of a black,This This thermal highlythermal cross-linkedrearrangement rearrangement residue is is depicted depicted and the inevolutionin Figure Figure 42. of42. phenolic products, and water. This thermal rearrangement is depicted in Figure 42.

FigureFigureFigure 42. 42.42. Thermal ThermalThermal degradation degradationdegradation mechanism mechanismmechanism of ofof PPE. PPE.PPE.

Polymer degradation and combustion are complex processes [65]. Two main degradation routes PolymerPolymer degradation degradation and and combustion combustion are are complex complex processes processes [65]. [65]. Two Two main main degradation degradation routes routes during pyrolysis are the formation of carbonaceous residue (char) and combustible vapors. In duringduring pyrolysispyrolysis areare the the formation formation of carbonaceousof carbonaceo residueus residue (char) (char) and combustible and combustible vapors. vapors. In general, In general, increasing the amount of char could reduce the generation of combustible gases, help to form general,increasing increasing the amount the ofamount char could of char reduce could the reduce generation the generation of combustible of combustible gases, help gases, to form help a thermalto form a thermal barrier between the condensed phase and the flame, limit the heat emitted by the pyrolysis abarrier thermal between barrier thebetween condensed the condensed phase and phase the flame, and th limite flame, the heatlimit emittedthe heat byemitted the pyrolysis by the pyrolysis reaction, reaction, decrease the solid’s conductivity of heat, and thus reduce the flammability of materials [66]. reaction,decrease decrease the solid’s the conductivity solid’s conduc of heat,tivity and of heat, thus and reduce thus the reduce flammability the flammability of materials of materials [66]. The [66]. char The char of the TPUs at 800 °C was measured by thermo-gravimetric analysis in nitrogen, as shown Theof the char TPUs of the at 800 TPUs◦C wasat 800 measured °C was measured by thermo-gravimetric by thermo-gravimetric analysis in nitrogen,analysis in as nitrogen, shown in as Figure shown 43 . in Figure 43. Char increased with increasing levels of PPE-M. The increased char could have inChar Figure increased 43. Char with increasingincreased levelswith ofincreasing PPE-M. Thelevels increased of PPE-M. char couldThe increased have implications char could for ease have of implications for ease of flame retarding and meeting flammability regulations. implicationsflame retarding for andease meetingof flame flammabilityretarding and regulations. meeting flammability regulations.

FigureFigureFigure 43. 43.43. Carbonaceous CarbonaceousCarbonaceous residue residueresidue (Char). (Char).(Char).

4.4.4. Conclusions ConclusionsConclusions PPEPPEPPE macromonomers macromonomers are areare unique unique hydrophobichydrophobic bisphenolsbibisphenolssphenols oror diols.diols. PPE-Ms PPE-Ms were werewere used usedused to toto synthesizesynthesizesynthesize novel novelnovel amphiphilic amphiphilicamphiphilic block blockblock copolymers. copolymers.copolymers. PPE-M PPE-MPPE-M was effective waswas effective ineffective broadly inin imparting broadlybroadly engineering impartingimparting engineeringpropertiesengineering to properties properties PHEs and to to TPUs. PHEs PHEs Theseand and TPUs. TPUs. novel These These ABCs no offernovelvel ABCs design ABCs offer offer engineers design design more engineers engineers flexibility more more in flexibility flexibility material inselection.in materialmaterial Indeed, selection.selection. these Indeed,Indeed, materials thesethese offer materialsmaterials new options offeroffer newnew for uniqueoptionsoptions combinations forfor uniqueunique combinationscombinations of performance ofof performancecharacteristics,performance characteristics,characteristics, such as high impact suchsuch as strengthas highhigh withimpactimpact excellent strengthstrength heat withwith resistance, excellentexcellent lower heatheat moisture resistance,resistance, absorption, lowerlower moistureandmoisture increased absorption, absorption, mechanical and and increased andincreased thermal mechanical mechanical properties. and and thermal thermal properties. properties. InIn addition addition to to the the hydrophilicity, hydrophilicity, PPE-M PPE-M exhibits exhibits PPE-philicity PPE-philicity and and polystyrene-philicity. polystyrene-philicity. These These featuresfeatures inin combinationcombination withwith thethe polyester-philicpolyester-philic andand hydrophilicityhydrophilicity ofof PHEPHE andand PUPU segmentssegments

Polymers 2017, 9, 433 21 of 24

In addition to the hydrophilicity, PPE-M exhibits PPE-philicity and polystyrene-philicity. These features in combination with the polyester-philic and hydrophilicity of PHE and PU segments demonstrated utility in compatibilization of alloys and improving the resin–filler interface adhesion in composites. A fruitful area for future ABC activity is in polymer blends and alloys. In general, blends and alloys of thermoplastics have an annual growth rate of 8–10% and constitute greater than 50% of the sales of plastics. Blends and alloys can be economically more attractive than to prepare copolymers or develop a totally new polymer. New products can be developed more rapidly by combining available polymers to produce desirable and novel [27,28]. The available degrees of freedom provide almost infinite possibilities and make the opportunity challenging. Properties of alloys are dependent on the nature of the polymers, interfacial attraction between the phases and the morphology. Properties can be additive (linear behavior) and based on the linear contribution from each polymer fraction. In addition, properties can exhibit a synergistic combination of properties (positive nonlinear behavior) where the properties are better than those predicted by linear behavior [25]. Clearly, interfacial adhesion is key in optimizing synergistic combination of properties [5]. Of particular interest are alloys of PPE. The PPE family of resins has become one of the most successful and best-known polymer blends and alloys. In general the PPE adds strength, lower moisture absorption, lower dielectric properties, increased dimensional stability, increased toughness, and increased thermal properties. These blends include both miscible and immiscible blends. The immiscible blends require improvements in interfacial adhesion. These PPE-philic ABCs could expand PPE alloys into new areas. For example, the PPE-philic and polyester-philic nature of PPE-PHE ABCs could enhance the performance of PPE alloys with other ester containing polymers which include recycled bottle grade of poly(ethylene terephthalate), polylactic acid, and polyethylene vinyl acetate. Another interesting area would be to explore the effect of ABCs on the resin–fiber adhesion in thermoset and other thermoplastic composites. For example, syndiotactic polystyrene is a semi-crystalline engineering thermoplastic and their GF grades suffered from poor mechanical properties—lower strength and stiffness, and weld line strength—relative to other engineering thermoplastics. These materials are handicapped by the lack of interfacial attraction between the glass fiber and the nonpolar, nonfunctional SPS. Thus, it would be beneficial to translate the performance enhancing capabilities of ABCs in GF–PS into SPS and other resin systems. The data in this review showed that over the range studied, higher molecular weight PPE segments gave better properties. In blends and composites, the data suggest that higher MW segments had increased interaction between the PS and PPE phases. It would be educational to further explore the effect of molecular weight to define the optimum composition. Indeed, the PPE-PHE ABCs were homogeneous with a single Tg. Understanding where the onset of phase separation occurs, the effect of molecular weight on phase separation, and the effect on performance should be explored.

Disclaimer: The materials, products and services of Saudi Basic Industries Corporation (SABIC) or its subsidiaries or affiliates (“Seller”) are sold subject to Seller’s standard conditions of sale, which are available upon request. Information and recommendations contained in this document are given in good faith. However, Seller makes no express or implied representation, warranty or guarantee: (i) that any results described in this document will be obtained under end-use conditions; or (ii) as to the effectiveness or safety of any design or application incorporating Seller’s materials, products, services or recommendations. Unless otherwise provided in Seller’s standard conditions of sale, Seller shall not be responsible for any loss resulting from any use of its materials, products, services or recommendations described in this document. Each user is responsible for making its own determination as to the suitability of Seller’s materials, products, services or recommendations for the user’s particular use through appropriate end-use and other testing and analysis. Nothing in any document or oral statement shall be deemed to alter or waive any provision of Seller’s Standard Conditions of Sale or this Disclaimer, unless it is specifically agreed to in a writing signed by Seller. Statements by Seller concerning a possible use of any material, product, service or design do not, are not intended to, and should not be construed to grant any license under any patent or other intellectual property right of Seller or as a recommendation for the use of any material, product, service or design in a manner that infringes any patent or other intellectual property right. SABIC and brands marked with ™ are trademarks of SABIC or its subsidiaries or affiliates, unless otherwise Polymers 2017, 9, 433 22 of 24 noted. Any brands, products or services of other companies referenced in this document are the trademarks, service marks and/or trade names of their respective holders. Conflicts of Interest: The authors declare no conflict of interest.

References

1. Peters, E.N. Polyphenylene Ether Blends and Alloys. In Engineering Plastics Handbook Thermoplastics, Properties, and Applications; Margolis, J., Ed.; McGraw-Hill: New York, NY, USA, 2006; pp. 181–220. 2. Peters, E.N.; Arisman, R.K. Engineering Thermoplastics. In Applied Polymer Science—21st Century; Craver, C.D., Carraher, C.E., Eds.; Elsevier: Amsterdam, The Netherlands, 2000; pp. 177–196. 3. Peters, E.N. Plastics: Thermoplastics, Thermosets, and Elastomers. In Handbook of Materials Selection; Kutz, M., Ed.; Wiley-Interscience: New York, NY, USA, 2002; pp. 335–355. 4. Peters, E.N. Poly(2,6-dimethyl-1,4-phenylene oxide). In Polymer Data Handbook, 2nd ed.; Mark, J.E., Ed.; Oxford University Press: Oxford, UK, 2009; pp. 534–538. 5. Peters, E.N. Engineering Thermoplastics—Materials, Properties, Trends. In Applied Plastics Engineering Handbook, 2nd ed.; Kutz, M., Ed.; Elsevier Inc.: Amsterdam, The Netherlands, 2016; pp. 3–26. 6. Peters, E.N.; Kruglov, A.; Delsman, E.; Guo, H.; Carrillo, A.; Rocha, G. Polyphenylene Ether Macromonomers. I. Property Enhancements in Thermoset Resins via Novel Telechelic Oligomers. In Proceedings of the 65th Annual Technical Conference & Exhibition, Society of Plastics Engineers, Cincinnati, OH, USA, 6–11 May 2007; pp. 2125–2128. 7. Peters, E.N.; Fisher, S.M.; Guo, H. Polyphenylene Ether Macromonomers. III. Enhancement of Dielectric Materials. In Proceedings of the IPC Printed Circuits EXPO & APEX, Las Vegas, NV, USA, 31 March–2 April 2009. 8. Peters, E.N.; Fisher, S.M.; Jestel, N.; Pietrafesa, M.; Guo, H. Polyphenylene Ether Macromonomers. II. Property Enhancements in Cyanate Ester Resins. In Proceedings of the 67th Annual Technical Conference & Exhibition, Society of Plastics Engineers, Chicago, IL, USA, 22–24 June 2009; pp. 611–614. 9. Peters, E.N.; Fisher, S.M.; Guo, H.; Degonzague, C.; Howe, R. Polyphenylene Ether Macromolecules. VII. Performance in t-Butyl Styrene/Divinyl Benzene Resin System. In Proceedings of the 68th Annual Technical Conference & Exhibition, Society of Plastics Engineers, Orlando, FL, USA, 16–20 May 2010; pp. 1858–1861. 10. Peters, E.N. PPE Macromonomers. XIV. Structure-Property Relationships in Epoxy Resins. In Proceedings of the Society of Plastics Engineers EUROTEC Conference, Lyon, France, 4–5 July 2013. 11. Peters, E.N.; Tarkin-Tas, E. PPE Macromonomers—Use in Anhydride cured epoxy. In Proceedings of the 72nd Annual Technical Conference & Exhibition, Society of Plastics Engineers, Las Vegas, NV, USA, 28–30 April 2014. 12. Peters, E.N.; Flanagan, J.; Denniston, M. Polyphenylene Ether Macromonomers: XIV. Preparation of Polyhydroxyether Block Copolymers. In Proceedings of the 70th Annual Technical Conference & Exhibition, Society of Plastics Engineers, Orlando, FL, USA, 2–4 April 2012. 13. DeKok, R.; Delsman, E.R.; Freshour, A.R.; Toublan, J.-J.F.; McCloskey, P.J.; Peters, E.N. Poly(arylene ether) Block Copolymer Compositions, Methods, and Articles. U.S. Patent Application 20080275185, 6 November 2008. 14. Peters, E.N. Polyurethane Foam and Associated Method and Article. U.S. Patent 9,266,997, 23 February 2016. 15. Peters, E.N. Rigid Foam and Associated Article. U.S. Patent 9,169,368, 27 October 2016. 16. Peters, E.N. Thermoplastic Polyurethane and Associated Method and Article. U.S. Patent 9,422,394, 23 August 2016. 17. Peters, E.N. Triblock Copolymer, Method for Its Formation, and Compatibilized Compositions Comprising It. U.S. Patent 8,865,823, 21 October 2014. 18. Reinking, N.H.; Barnabeo, A.E.; Hale, W.F. Polyhydroxyethers. I. Effect of Structure on Properties of High Molecular Weight Polymers from Dihydric Phenols and Epichlorohydrin. J. Appl. Polym. Sci. 1963, 7, 2135–2144. [CrossRef] 19. Batzer, H.; Zahir, S.A. Studies in the molecular weight distribution of epoxide resins. III. Gel permeation chromatography of epoxide resins subject to post glycidylation. J. Appl. Polym. Sci. 1975, 19, 609–617. 20. Burchard, W.; Bantle, S.; Zahir, S.A. Branching in high molecular weight polyhydroxyethers based on bisphenol A. Makromol. Chem. 1981, 182, 145–163. [CrossRef] Polymers 2017, 9, 433 23 of 24

21. Senger, J.S.; Subramanian, R.; Ward, T.C.; McGrath, J.E. Synthesis and Determination of Chain Branching in Linear High Molecular Weight Polyhydroxyethers. In Polymer Preprints, Division of Polymer Chemistry. Am. Chem. Soc. 1986, 27, 144–146. 22. ASTM International Voluntary Organization D2572-97. Standard Test Method for Isocyanate Groups in Urethane Materials or Prepolymers; ASTM International: West Conshohocken, PA, USA, 2010. 23. Peters, E.N.; Flanagan, J.; Guise, O. Amphiphilic PPE-PHE Block Copolymers as Compatibilizers for Polyester Blends. In Proceedings of the 72nd Annual Technical Conference & Exhibition, Society of Plastics Engineer, Las Vegas, NV, USA, 28–30 April 2014. 24. Peters, E.N.; Bajaj, P.; Flanagan, J.; Pecak, W. Polyphenylene Ether Macromonomers: XV. Enhancement of PS/GF Composites by PPE-PHE Block Copolymers. In Proceedings of the 72nd Annual Technical Conference & Exhibition, Society of Plastics Engineers, Las Vegas, NV, USA, 28–30 April 2014. 25. Peters, E.N. Introduction to Polymer Characterization. In Comprehensive Desk Reference of Polymer Characterization and Analysis; Brady, R.F., Jr., Ed.; Oxford University Press: Oxford, UK, 2003; pp. 3–29. 26. Potschke, P.; Wallheinke, K.; Fritsche, H.; Stutz, H. Morphology and properties of blends with different thermoplastic polyurethanes and polyolefines. J. Appl. Polym. Sci. 1997, 64, 749–762. [CrossRef] 27. Shonaike, G.O.; Simon, G.P. Polymer Blends and Alloys; Society of Plastics Engineers: Brookfield, CT, USA, 1999. 28. Olabisi, O.; Robeson, L.M.; Shaw, M.T. Polymer-Polymer Miscibility; Academic Press: Cambridge, MA, USA, 1979. 29. Solc, K. Polymer Compatibility and Incompatibility: Principles and Practice; Harwood Academic Publishers GmbH: New York, NY, USA, 1982. 30. Peters, E.N. Compatibilized Composition, Method for the Formation Thereof, and Article Comprising Same. U.S. Patent 8552105 B2, 8 October 2013. 31. Melton, G.; Peters, E.N.; Arisman, R.K. Engineering Thermoplastics. In Applied Plastics Engineering Handbook; Kutz, M., Ed.; Elsevier: Amsterdam, The Netherlands, 2011; pp. 7–21. 32. Robeson, L.M. Polymer Blends: A Comprehensive Review; Hanser: Cincinnati, OH, USA, 2007. 33. Harris, J.E.; Goh, S.H.; Paul, D.R.; Barlow, J.W. Miscible binary blends containing the polyhydroxy ether of bisphenol-A and various aliphatic polyesters. J. Appl. Polym. Sci. 1982, 27, 839–855. [CrossRef] 34. Robeson, L.M.; Furtek, A.B. Miscible Blends of poly(butylene terephthalate) and the Polyhydroxyether of Bisphenol A. J. Appl. Polym. Sci. 1979, 23, 645–659. [CrossRef] 35. Christiansen, W.H.; Paul, D.R.; Barlow, J.W. The phase behavior of ternary blends containing polycarbonate, phenoxy, and polycaprolactone. J. Appl. Polym. Sci. 1987, 34, 537–548. [CrossRef] 36. Uriarte, C.; Eguiazábal, J.I.; Llanos, M.; Iribarren, J.I.; Iruin, J.J. Miscibility and phase separation in poly(vinyl methyl ether)/poly(bisphenol A hydroxy ether) blends. Macromolecules 1987, 20, 3038–3042. [CrossRef] 37. Snodgrass, H.E.; Lauchlan, R.L. Polyphenylene Oxide Resins Modified with Polyhydroxy Ethers. U.S. Patent 3,631,126, 28 December 1971. 38. Moskala, E.J.; Coleman, M.M. FTIR Studies of Polyvinyl ether Blends with the poly(hydroxyl ether of Bisphenol A). Polym. Commun. 1983, 24, 206–208. 39. Coleman, M.M.; Moskala, E.J. FTIR Studies of Polymer Blends Containing the poly(hydroxyl ether of bisphenol A) and Poly(ε-caprolactone). Polymer 1983, 24, 251–257. [CrossRef] 40. Kim, H.C.; Nam, K.H.; Jo, W.H. The effect of a styrene-methyl methacrylate block copolymer on the morphological, rheological and mechanical properties of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(hydroxy ether of bisphenol A) (Phenoxy) blends. Polymer 1993, 34, 4043–4051. [CrossRef] 41. Gallucci, R.; Hamilton, D.G. The effects of molecular weight on polycarbonate-polybutylene terephthalate blends. J. Appl. Polym. Sci. 1993, 48, 2249–2252. 42. Plueddemann, E.P. Silane Coupling Agents, 2nd ed.; Springer: New York, NY, USA, 1991. 43. Fowkes, F.M. Quantitative characterization of the acid-base properties of solvents, polymers, and inorganic surfaces. J. Adhes. Sci. Technol. 1990, 4, 669–691. [CrossRef] 44. Takemori, M.T. Towards an understanding of the heat distortion temperature of thermoplastics. Polym. Eng. Sci. 1979, 19, 1104–1109. [CrossRef] 45. Takemori, M.T. Towards an Understanding of the Heat Distortion Temperature of Thermoplastics, Filled and Unfilled; General Electric: Boston, MA, USA, 1976. 46. Chang, F.C.; Yang, M.Y. Mechanical fracture behavior of polyacetal and thermoplastic polyurethane elastomer toughened polyacetal. Polym. Eng. Sci. 1990, 30, 543–552. [CrossRef] Polymers 2017, 9, 433 24 of 24

47. Agrawal, R.K.; Drzal, L.T. Adhesion mechanisms of polyurethanes to glass surfaces. III. Investigation of possible physico-chemical interactions at the interphase. J. Adhes. 1996, 55, 221–243. [CrossRef] 48. Houvenaghel, G.; Carmeliet, J. Dynamic Contact Angles, Wettability and Capillary Suction of Hydrophobic Porous Materials. In Proceedings of the Hydrophobe III—3rd International Conference on Surface Technology with Water Repellent Agents, Aedificatio Publishers, Freiburg, Germany, 25–26 September 2001; pp. 191–200. 49. Förch, R.; Schönherr, H.; Tobias, A.; Jenkins, A. See Appendix C. In Surface Design: Applications in Bioscience and Nanotechnology; Wiley-VCH: Weinheim, Germany, 2009; p. 471. 50. Frisch, K.C.; Sendijarevic, A.; Sendijarevic, V.; Yokelson, H.B.; Nubel, P.O. Polyurethane Elastomers Based Upon Novel Hydrocarbon-Based Diols. In Proceedings of the Conference UTECH 96, The Hague, The Netherlands, 26–28 March 1996; p. 42. 51. Yokelson, H.B.; Nubel, P.O.; Sendijarevic, A.; Sendijarevic, V.; Frisch, K.C. Novel Hydrocarbon-Based Diols for Polyurethane Elastomers. In Proceedings of the SPI Polyurethanes 1995 Conference, Chicago, IL, USA, 26–29 September 1995. 52. Adhikari, R.; Gunatillake, T.; Mccarthy, S.; Meijs, G.F. Mixed macrodiol-based siloxane polyurethanes: Effect of the comacrodiol structure on properties and morphology. J. Appl. Polym. Sci. 2000, 78, 1071–1082. [CrossRef] 53. Trombetta, T.; Scicchitano, M.; Simeone, G.; Ajroldi, G. New fluorinated thermoplastic elastomers. J. Appl. Polym. Sci. 1996, 59, 311–327. 54. Alves, P.; Pinto, S.; de Sousa, H.C.; Gil, M.H. Surface modification of a thermoplastic polyurethane by low-pressure plasma treatment to improve hydrophilicity. J. Appl. Polym. Sci. 2011, 122, 2302–2308. [CrossRef] 55. Bolland, J.L.; Gee, G. Kinetic studies in the chemistry of rubber and related materials. II. The kinetics of oxidation of unconjugated olefins. Trans. Faraday Soc. 1946, 42, 236–243. [CrossRef] 56. Gryn’ova, G.; Hodgsona, J.L.; Coote, M.L. Revising the mechanism of polymer autooxidation. Org. Biomol. Chem. 2011, 9, 480–490. [CrossRef][PubMed] 57. Levchik, S.V.; Weil, E.D. Thermal decomposition, combustion and fire-retardency of polyurethanes—A review of the recent literature. Polym. Int. 2004, 53, 1585–1610. [CrossRef] 58. Chambers, J.; Jiricny, J.; Reese, C.B. The thermal decomposition of polyurethanes and polyisocyanurates. Fire Mater. 1981, 5, 133–141. [CrossRef] 59. Wang, H.; Wang, Q.; He, J.; Mao, Z. Study on the Pyrolytic Behaviors and Kinetics of Rigid Polyurethane Foams. Procedia Eng. 2013, 52, 377–385. [CrossRef] 60. Grassie, N.; Mendoza, G.A.P. Thermal degradation of polyether-urethanes: Part 1—Thermal degradation of poly(ethylene glycols) used in the preparation of polyurethanes. Polym. Degrad. Stab. 1984, 9, 155–165. [CrossRef] 61. Jachowicz, J.; Kryszwski, M.; Kowlaski, P. Thermal degradation of Poly(2,6-dimethyl-1,4-phenylene oxide). I. The mechanism of degradation. J. Appl. Polym. Sci. 1978, 22, 2891–2899. [CrossRef] 62. Factor, A. The high-temperature degradation of poly(2,6-dimethyl-1,4-phenylene ether). J. Polym. Sci. Part A 1969, 7, 363–377. [CrossRef] 63. Murashko, E.A.; Levchik, G.F.; Levchik, S.V.; Bright, D.A.; Dashevsky, S. Fire Retardant Action of Resorcinol Bis(Diphenyl Phosphate) in a PPO/HIPS Blend. J. Fire Sci. 1998, 16, 233–249. [CrossRef] 64. Weil, E.D.; Levchik, S. A Review of Current Flame Retardant Systems for Epoxy Resins. J. Fire Sci. 2004, 22, 25–40. [CrossRef] 65. Cullis, C.F.; Hirschler, M.M. The Combustion of Organic Polymers; Clarendon Press: Oxford, UK, 1981. 66. Van Krevelen, D.W. Some basic aspects of flame resistance of polymeric materials. Polymer 1975, 16, 615–620. [CrossRef]

© 2017 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).