MASTER's THESIS Blends of EPDM Rubber/Thermoplastics

2008:106 MASTER'S THESIS

Blends of EPDM rubber/Thermoplastics

Jinxia Li

Luleå University of Technology Master Thesis, Continuation Courses Advanced material Science and Engineering Department of Applied Physics and Mechanical Engineering Division of Polymer Engineering

2008:106 - ISSN: 1653-0187 - ISRN: LTU-PB-EX--08/106--SE TABLE OF CONTENT PREFACE ...... I

ABSTRACT...... II

LIST OF TABLES AND FIGURES...... III

ABBREVIATION...... V

I. INTRODUCTION ...... 1

I.1. Recycling of rubber...... 1 I.2. Rubber Recycling by Blending with Plastics...... 3 I.3. Compatibilization...... 5 I.3.1 nonreactive compatibilizers ...... 9 I.3.2 reactive compatibilizers ...... 11 I.4. Blending methods ...... 16

II. OBJECTIVES...... 18

III. MATERIALS AND METHODS...... 19

III.1. Materials...... 19 III.2. Methods...... 20 III.2.1. Specimens...... 20 III.2.2. Mechanical testing procedures...... 20 III.2.3. SEM analysis...... 23 III.2.4. DSC analysis ...... 23 III.2.5. Compressive set testing...... 23

IV RESULTS AND DISCUSSION ...... 25

IV.1 Non-reactive compatibilization...... 25 IV.2 Reactive compatibilization...... 31 IV.3 Effect of pressing pressure during plate production ...... 38 IV.4 Effect of unvulcanized rubber...... 39 IV.5 Microstructure analysis...... 41 IV.6 Comparison of the properties between LDPE/EPDM and EMA/EPDM blends ...... 43

A V. CONCLUSIONS ...... 49

VI. FUTURE WORK...... 51

VII. REFERENCES ...... 52

Appendix A1. Low density polyethylene data sheet...... 56

Appendix A2. EMA copolymer data sheet ...... 57

Appendix B. EXACT 0210 data sheet ...... 59

Appendix C. SP-1045 & HRJ -10518 data sheet ...... 60

Appendix D. SAMPLE LIST (wt%)...... 62

Appendix E. Price Index list of materials (reference value only) ...... 64

B PREFACE

This thesis was carried out at the Division of Polymer Engineering at Luleå University of

Technology during the period from February 2008 to October 2008.

First of all, I would like to give my special thanks to my supervisor Dr. Lennart Wallström, for his academic instructions and all the support during this thesis.

I also thank Mr. Johnny Grahn, Lars Frisk and Roberts Joffe for their technical support and instructions.

I also would like to thank all my colleagues at the Polymer Division for all the help they gave me.

This thesis is part of AMASE Master Program, which is financed by European

Commission and is gratefully acknowledged.

Finally, I wish to express my gratitude to my family for all their support and encouragement.

I ABSTRACT Blends containing recycled EPDM rubber and thermoplastics, EMA and LDPE were studied. Two compatibilization methods, reactive and non-reactive, were evaluated. Ethylene octene copolymer (EXACT 0210) was used as non-reactive compatibilizer. Phenolic resins

(SP1045 & HRJ10518) were reactive agents. There existed an optimal composition of compatibilizers which were 25wt% in the case of reactive and non-reactive agents added to

15wt%EMA and 55-60wt% EPDM rubber. EXACT-compatibilized blends gave high elongation at break while phenolic resin-compatibilized mixtures gave high stiffness in comparison with the chosen reference material. Comparison in compatibilizing capabilities

HRJ-10518 and SP-1045 was carried out. The former one had better capabilities than the latter at high compatibilizer content. Talcum was used as anti-agglomeration agent but failed to work properly. Pressing pressure could be minimized without any adverse effect. Non- vulcanized rubber was used to enhance tear strength but its effect was small by assuming that there exists degradation of the interfacial surface at high temperature. SEM analysis revealed homogeneous microstructure in both kinds of compatibilization. EXACT 0210-compatibilized blends showed more plastic deformation of the matrix than reactive blends. Stable connection between phases was also observed. Tensile strength of the LDPE based blends were a little lower than that of EMA based blends and the hardness was a little higher. Compared to EMA based blends, the elongation at break was much lower while the young’s modulus was much higher with LDPE based blends. Compression set of both LDPE and EMA based blends was high compared to the reference materials.

Key words:

Recycled EPDM rubber, unvulcanized rubber, LDPE, EMA, reactive compatibilization, non- reactive compatibilization, ethylene octene copolymer, phenolic resins, tensile properties, tear strength, microstructure, pressing pressure

II LIST OF TABLES AND FIGURES

Figure 1.1: Chemical structure of EPDM 2 Figure 1.2: Image of recycled EPDM rubber under microscopy 3 Figure 1.3: Various copolymer grades visible at the boundary layer of two 8 polymers Figure 1.4: Effect of polar compatibilizer type and compatibilizer loading on 9 Charpy notched impact strength (kJ/m2) of PP/ midsole compounds Figure 1.5: Effect of nonpolar compatibilizer type and compatibilizer loading on 10 Charpy notched impact strength (kJ/m2) of PP/scrap dust compounds Figure 1.6:Reactive groups commonly encountered in reactive compatibilization 14 Figure 1.7: Tensile strength of thermoplastic vulcanizates of 60/40 NR/HDPE 15 blends with various types of blend compatibilizers Figure 1.8: Elongation of thermoplastic vulcanizates of 60/40 NR/HDPE blends 15 with various types of blend compatibilizers Figure 3.1: Standard dumbbell die C for tensile strength test (ASTM-D412-06a) 22 Figure 3.2: Standard die T for tear strength test (ASTM-D 624-91) 22 Figure 4.1: Comparison of tear strength between different non-reactive 25 compatibilizers Figure 4.2: Tensile strength of recycled EPDM rubber/EMA blends 26 compatibilized by EXACT Figure 4.3: Elongation at break of recycled EPDM rubber/EMA blends 26 compatibilized by EXACT Figure 4.4: Young’s Modulus of recycled EPDM rubber/EMA blends 27 compatibilized by EXACT Figure 4.5: Tear strength of recycled EPDM rubber/EMA blends compatibilized 27 by EXACT Figure 4.6: Hardness of recycled EPDM rubber/EMA blends compatibilized by 28 EXACT Figure 4.7 : Stress-elongation relationship of recycled EPDM rubber/EMA 30 blends compatibilized by EXACT Figure 4.8: Effect of talcum on the mechanical properties of 70wt% EPDM 31 rubber + 15wt%EXACT+ 15wt% EMA Figure 4.9: Molecular structure of reactive agents 33

III Figure 4.10: Tensile strength of recycled EPDM rubber/EMA blends 33 compatibilized by reactive agent Figure 4.11: Elongation at break of recycled EPDM rubber/EMA blends 34 compatibilized by reactive agent Figure 4.12: Tear strength of recycled EPDM rubber/EMA blends 34 compatibilized by reactive agent Figure 4.13: Young’s Modulus of recycled EPDM rubber/EMA blends 35 compatibilized by reactive agent Figure 4.14: Hardness of recycled EPDM rubber/EMA blends compatibilized by 35 reactive agent Figure 4.15: Mechanical properties of recycled tired rubber/EMA blends 36 compatibilized by reactive agents Figure 4.16: Comparison of mechanical properties of recycled EPDM rubber / 37 EMA blends Figure 4.17: Effect of pressure on the mechanical properties of recycled EPDM 39 rubber/EMA blends Figure 4.18: Effect of unvulcanized rubber and blending temperature on tear 40 strength of recycled EPDM rubber/EMA blends Figure 4.19: DSC analysis of unvulcanized rubber, scanning rate 10 0C /min 41 Figure 4.20: SEM images of recycled EPDM rubber/EMA blends 42

Figure 4.21: Phase connection of recycled EPDM rubber/EMA blends 43 Figure 4.22:Mechanical properties of the blends: EMA/EPDM/EXACT and 44 LDPE/EPDM/EXACT Figure 4.23: Mechanical properties of the blends: EMA/EPDM/DRM and 45 LDPE/EPDM/HRJ Figure 4.24: Mechanical properties of the blends: EMA/EPDM and 46 LDPE/EPDM ( the blends with HRJ contain 4wt% additives) Figure 4.25: Comparison of compression set under different temperature: A 55 47 0C B Room temperature 23 0C

Table 1: Compounding formulation used to prepare rubber/thermoplastics 21 blends Table 2: Mixing schedule (descending order) 21

IV ABBREVIATION EMA Copolymer of ethylene and methyl acrylate

EPDM Ethylene Propylene Diene

PE Polyethylene

PP Polypropylene

POE Poly Olefin Elastomer

EVA Ethylene Vinyl Acetate

PVC Polyvinyl chloride

SBR Styrene Butadiene Rubber

SRP Synthetic rubber powder

TPE Thermo Plastic Elastomer

EXACT EXACT 0210, Ethylene based Octene Plastomer

Phenolic resion with active hydroxymethyl (methylol) HRJ groups (HRJ-10518) Dimethylol phenolic resin or octylphenol-formaldehyde SP resin (SP-1045)

V I. INTRODUCTION

I.1. Recycling of rubber

The problem of recycling rubber has existed since Charles Goodyear first discovered vulcanization in 1839. Disposal of used rubber into landfills has become increasingly prohibitive due to high costs, legislative pressures, public opinion, especially high environmental stress. Researchers pay much attention to recycling. Many rubber products are now recycled such as used tires.

Rubber recycling encompasses a range of rubber types, Scheirs [2] pointed out that approximately 94% of all the rubber consumed in the world was thermoset in nature and thermoplastic elastomers comprise the remaining 6% of rubber products. Besides automotive tires, other thermoset rubber articles that are entering the recycle stream include drive belts, automotive hoses and a variety of fabric reinforced components.

The first most important step is processing or reduction of whole tires into useful particle sizes. Sadhan [1] noted that the processes used for grinding of rubber are based on cutting, shearing, or impact, depending on the equipment and the grinding conditions. There were cutting, milling, extrusion, ambient and wet grinding, cryogenic grinding, etc.

Shredded tires are used as filler material in highway construction because they increase the abrasion resistance and enhance the resilience. Concentrations of tire rubber used for these purposes are 10% to 20%. [1]

Cross-linked networks rubber could be recycled via high-pressure, high-temperature sintering (HPHTS) process [1]. The rubber powder in HPHTS is believed to “sintering” due to rearrangement of chemical bonds across the rubber particle interfaces at elevated temperatures.

1 Since the development of a tire vacuum pyrolysis process from the laboratory to the industrial scale, the used tires could be converted to carbon black and oil by pyrolysis [1].

Ethylene propylene rubber EPM is a copolymer consisting of ethylene and propylene units as part of the main polymer chain. [29] It can be cross-linked with peroxides or radiation but not sulfur. EPM is used as an ethylene based plastic impact modifier and as a viscosity index improver for lubricating oils. When a non-conjugated diene is grafted on to the main polymer chain it becomes a terpolymer, ethylene propylene diene (EPDM, figure 1.1) and interchain sulfur cross-linking becomes possible. EPDM is largely unaffected by weather with very good resistance to ozone. Low temperature flexibility is very good and compares well with NR, and like NR and SBR, EPDM (with a lower polarity than NR) has very poor oil resistance. [29]

Figure 1.1: Chemical structure of EPDM [29]

The image of the recycled EPDM rubber powder used in this project under microscopy was shown in Figure 1.2. The recycled EPDM rubber was produced by grinding EPDM rubber and the size is less than 0.1 mm. The focus on this work was to recycle the EPDM rubber by blending it with thermoplastic polymer to form the Thermoplastic/rubber-blends.

2 0.1 mm

Figure 1.2: Image of recycled EPDM rubber under microscopy

I.2. Rubber Recycling by Blending with Plastics

The best way to recycle rubber products would be to devulcanize and reuse them in the rubber industry [1]. Processes for devulcanization, including chemical, thermal, thermomechanical, and ultrasonic, have been worked out, but they are costly and not suitable for commercial application, particularly in manufacturing highly engineered produces like tire.

Sadhan [1] summed up that other alternative is to blend the crumb or ground rubber with a material having the ability to flow under heat and pressure, so that it can be shaped into useful articles at a reasonable cost. This can be accomplished by mixing finely ground rubber with plastics, along with necessary additives.

Thermoplastic elastomers (TPEs) combine the elastic and mechanical properties of thermoset crosslinked rubbers due to the melt processability of thermoplastics. Today, TPEs comprise the fastest growing rubber market. TPEs can be processed by a variety of techniques, such as extrusion blow moulding, injection moulding, vacuum forming and calendaring. So, production scrap and waste rubber after use can be recycled. Thermoplastic vulcanisates

3 (TPVs) are a particular family of TPEs, which are produced via dynamic vulcanization of non-miscible blends of a rubber and a thermoplastic, i.e. the selective crosslinking of the rubber while simultaneous melt mixing with the thermoplastic [3].

In recent years, TPEs and TPVs have replaced conventional rubbers in a variety of applications including appliance, automotive, medical, engineering, etc.[1] TPEs are made by copolymerization and by blending thermoplastics with a rubbery component. TPVs, on the other hand, are made by dynamically vulcanizing the rubber component in a rubber/thermoplastic blend during mixing. Sadhan [1] pointed out that both materials are processed like thermoplastics and are recyclable.

Thermoplastic elastomers (TPEs) exhibit the functional properties of conventional elastomeric material and can be processed with a thermoplastic processing machine [4].

Bhowmick and co-workers [6] considered that the plastic acts as a continuous phase allows for melt processing of the TPEs, whereas the dispersed rubber phase is responsible for rubber elasticity and other elastomeric properties of the blends. Various types of thermoplastics are used to prepare TPEs. These include polypropylene, low-density polyethylene, ultra-low- density polyethylene, linear low-density polyethylene, chlorinated polyethylene, polystyrene, polyamide, ethylene vinyl acetate (EVA) copolymer and poly (methyl methacrylate). [4]

Ethylene methylacrylate copolymer is one of the most thermostable olefin copolymers. It is used for the manufacture of films and sheets, for injection molding, extrusion coating and coextrusion. Some of the most lasting effects of the addition of EMA are the lowering of the

Vicat temperature, the reduction of the flexural modulus of elasticity, a noticeable improvement in resistance to stress cracking. The thermal stability of the material is so high that temperatures of 315 to 330 0C can be used for extrusion coating. What is more, with a melting temperature of 150 0C EMA can be processed on normal LDPE plant to tubular

4 film.[9] We choose EMA to blend with EPDM rubber due to its thermal stability and good mechanical properties.

Thermoplastics such as PE, PP, and PVC are not only cheap, but also are available in a wide range of melt index and micro-structure, which can be used for blending with recycled rubber. In addition, a substantial quantity of commodity and engineering plastics is available as recyclate from municipal solid waste and manufacturing waste. This can be used to blend with scrap rubber, to further reduce product cost and alleviate the current environmental problems.[1] Considering the low cost, we choose LDPE to blend with EPDM rubber.

In short, there is a great scope for recycling both devulcanized rubber and ground rubber by blending with plastics. Whereas devulcanized rubber will act as a second polymeric component, vulcanized ground-rubber particles will act as a low-cost organic filler or extender. Polymeric in nature, ground-rubber particles provide additional advantage over inorganic fillers such as carbon black, talc, or silica for bonding better with matrix polymer- after suitable chemical or mechanical treatment or in the presence of a compatibilizer.[1]

I.3. Compatibilization

Datta and Lohse[5] has expressed that the earliest theories of the theories of the thermodynamics of polymer mixtures (blends and solutions) date back to 1941. The main equation is the Flory-Huggins-Staverman (FHS) expression for the free energy of mixing two polymers:

ΔGm φ1 φ2 χ = lnφ1 + ln + φφφ 212 ν NVRT 11 ν N22 ν

Here V is the total volume of the sample, R is the gas constant, T is the absolute

temperature, Ni is the degree of polymerization of component i (=1 or 2), φi is the volume

5 fraction of that component, υi is the molar volume of its monomers, and υ is an arbitrary

reference volume (often defined as νν 21 ). The first two terms represent the combinatorial entropy of mixing, and the last term comes from the interaction enthalpy; χ is called the Flory interaction parameter.

The first of these successes is an explanation of why most polymer blends show essentially no region of miscibility. Since most polymers of commercial interest have degrees of polymerization of 1000 or more, the first two terms representing the entropy of mixing are generally quite small. Datta and lohse [5] has discussed 5 kinds of polymer blend phase diagram types, and most of their phase diagram is of the “hourglass” type.

Much of the attention must be placed on the interfacial region between the phases in a multiphase blend. [5] Firstly, the interactions between the phases occur across the interface, and so the driving force of phase separation is located there. This generally expressed as an interfacial tension between the phases, and one of the main mechanisms of compatibilization is to reduce the interfacial tension between the phases. Further more, the mechanical behavior of the multiphase system will depend critically on the nature of the interface and its ability to transmit stresses from one phase to the other. As in many other cases (spherulite boundaries in semicrystalline material, grain boundaries in metals), the phases is an important determinant of how the blend will respond to stress, that is, of mechanical properties such as tensile strength and toughness. [5]

Sadhan et al. [1] had the opinion that the key to success in blending rubber with plastics is to compatibilize the two components to get satisfactory performance. Since most polymers, including elastomers, are high-molecular-weight compounds and are thermodynamically immiscible with each other, their blends undergo phase separation, with poor adhesion

6 between the matrix and dispersed phase. The properties of such blends are often inferior to those of the individual components.

Miscibility between the two polymers is best accomplished either by reducing the heat of mixing or by making it negative. Compatibilization may be described as a process that reduces the enthalpy of mixing or making it negative. This is best accomplished either by adding a third component, called a compatibilizer, or by enhancing the interaction of the two component polymers, chemically or mechanically. [1]

Sadhan et al. [1] summarized that the role of the compatibilization is to:

A. Reduce interfacial energy and improve adhesion between phases.

B. Achieve finer dispersion during mixing. In blending recycled rubber with plastics, smaller particle size of the ground rubber and deagglomeration during mixing play a major role.

C. Stabilize the fine dispersion against agglomeration during processing and throughout the service life.

D. The ultimate objective is to develop a stable morphology that will facilitate smooth stress transfer from one phase to the other and allow the product to resist failure under multiple stresses.

In Brandrup’s opinion [7], if a compatibilizer is to be certain to function, its structure has to be as simple as possible. It can be assumed here that AB diblock copolymers and single graft copolymers are more suitable than ABA triblock copolymers and these in turn are better than multiple graft copolymers and multiple block copolymers. A compatibilizer usually only has a short time to accumulate at the boundary surface and penetrate into the matrix and into the

7 disperse phase. It should be obvious from the foregoing that simple compatibilizers such as

AB diblock copolymers and single graft copolymers are the most effective.

Good compatibilizers have a tendency to exhibit phase separation. Block and graft copolymers are most suitable; they can be added or prepared in situ. A compatibilizer consists, for example, of one block with an affinity for polymer A and one block with an affinity for polymer B. in the case of graft copolymers, the main chain mixes with one phase and the grafts with the other.[7](Figure 1.3)

Figure 1.3: Various copolymer grades visible at the boundary layer of two polymers.

(Brandrup, 1996 [7])

Brandrup[7] argued that high-molecular compatibilizer are more expensive than low- molecular ones, to obtain a surface-tension reducing effect, more high-molecular weight material is require; with longer chains, it is at the same time more difficult to accumulate a sufficient number of chains at the boundary layer. In general there is an optimum molecular weight, which depends on the characteristics of the blend components.

In general, compatibilization of two dissimilar polymeric materials is carried out either by mechanical or by chemical methods, or by both simultaneously.

8 I.3.1 nonreactive compatibilizers

As nonreactive compatibilizer, an external plasticizer or a polymeric material such as a copolymer (preferably a block copolymer, which has chain units similar to both components of the blend) is added to the blend to achieve compatibilization [1]. Although in many instance tri-block copolymers (such as styrene-ethylene-butylene-styrene) have also been used [8], as have random and graft copolymers. Block and graft copolymers reduce the interfacial tension by spreading at the interface and mixing with both phases through their component parts which are similar to one phase or the other [1]. In the case of a block copolymer, the chemical structures of the individual blocks also play an important role. The closer the chemical structure of the blocks to the chemical structure of the blocks to the chemical structures of the blend components, the better the compatibilization [1].

Figure 1.4: Effect of polar compatibilizer type and compatibilizer loading on Charpy notched impact strength (kJ/m2) of PP/ midsole compounds [8]

Figure 1.5: Effect of nonpolar compatibilizer type and compatibilizer loading on Charpy notched impact strength (kJ/m2) of PP/scrap dust compounds. [8]

In P. Phinyocheep’s work [8], the influence on the impact strength of different types of compatibilizer was shown in Figure 1.4 and 1.5. It is intuitively obvious that SEBS-g-MA

(kraton) gave the best impact strength of PP/scrap rubber dust compounds (Figure 1.4) and the compounds compatibilized with SEBS (kraton) have the higher impact strength than with

SBS. These were explained that the EB midblock of the SEBS copolymer gave better compatibility with PP than the B (butadiene) midblock of the SBS copolymer.

Li and co-workers, [10] who examined the compatibilization of Styrene-Butadiene-Styrene block copolymer in Polypropylene and polystyrene blends, showed that the copolymer having segments at least partially miscible with the particular component of the blend system were

10 located between homopolymers and formed the interface layer. The localization of the copolymer at the interface with the block or graft extending into their interface with the block or graft extending into their respective homopolymer phases not only minimizes the contacts between the unlike segments of the copolymer and homopolymer but also displaces the two homopolymer away from the interface, thereby decreases the enthalpy of mixing between homopolymers, which leads to a better compatibility between phases as well as fine and more stable morphology.

Li et al. [11] has studied the compatibilization effect of EVA and ethylene-octylene copolymer (POE) on the morphology and mechanical properties of HDPE and scrap rubber powder (SRP) blends, concluded that POE encapsulated SRP Particles and some other POE dispersed uniformly; while EVA and SRP dispersed separately. Both the impact strength and elongation at break were higher in POE compatibilization than in EVA compatibilization.

I.3.2 reactive compatibilizers

Mangaraj [1] gave the definition of reactive compatibilization that is carried out during the blending process by adding a reactive material as a blend component.

Harrats[12] pointed out that physical blending consists of adding a pre-formed copolymer to compatibilize the blend and reactive blending is based on the in-situ generation of the compatibilizing agent. In-situ copolymer formation and compatibilization activity are discussed in terms of the effect of: - the miscibility of the compatibilizer precursor, - the configuration of reactive end groups and, - the content of reactive groups.

In reactive blending, the compatibilization of immiscible polymers is ensured by a chemical reaction initiated during the process of melt-mixing. The in situ formed compatibilizing agent (block or graft copolymer, crosslinked species, ionic associations, etc.) reduces the interfacial tension between the immiscible blend components, enhances the

11 adhesion between the phases and, as a consequence, imparts to the blend acceptable mechanical properties. [12-15]

Reactive blending is a very cost-effective process that allows the formulation of new multiphase polymeric materials. [12] The copolymer responsible for compatibilization of the blend components is formed in-situ during the melt-process. It is expected that the reactive precursors generate the compatibilizing block or graft copolymer at the interface of the immiscible polymer blend. As a consequence, micelle formation in one or the other phase is expected to be minor compared to when the pre-made block or graft copolymers are used, which can easily self-organize in the phase where they are the most energetically stable. This situation is expected to be more probable in extrusion processes where the residence time is short so that the mixing equilibrium is often not completely attained.

In this case compatibilization is ensured via the in-situ formation of a block or a graft copolymer during the process of melt-mixing, through an interfacial chemical reaction between functional groups available on the polymer chains in the blend system. The functional groups should be selected so that the interfacial reaction occurs within a few minutes frame tolerated for the processing operation. The generated interchain bonding must be stable enough to survive the thermal and shearing treatment during the process of blending.

That is due to the limited yield of the interfacial reaction due to the short extrusion time and low molecular diffusion, highly reactive groups are required. [12]

It is very important to keep the kinetics and yield aspects of the interfacial reaction in reactive compatibilization, which means each blend system has its own ‘pack’ of experimental conditions such as mixing time, mixing temperature, screw design, molecular weight and reactive group content of the precursors. Although the experimental tuning is severe, the control of the molecular structure of the compatibilizer generated in-situ remains

12 qualitative. Reactive compatibilization has several advantages, mostly economical, over the nonreactive compatibilization [12]:

a. The copolymer is made as needed during the melt-blending process and a separate

commercialization of a copolymer is not required.

b. The copolymer is formed directly at the interface between the immiscible polymers

where it is needed to stabilize the phase morphology developed. In contrast, when a

compatibilizing copolymer is added as a separate entity to a blend, it must

overcome the viscous forces and diffuse to its expected location at polymer-

polymer interface. It may, however, form micelles as a separate phase that is

useless for compatibilization.

c. A second fundamental advantage of in-situ copolymer formation is that the

molecular weight of each of the two distinct polymeric segments in the copolymer

is usually the same as that of the individual bulk polymer phase in which the

segment must dissolve allowing, thus, for a maximum interfacial adhesion.

The main disadvantage of reactive blending resides in the need to have reactive functional groups on the polymers to be compatibilized.

Harrats [12] summarized the most commonly used pairs of reactive group in reactive compatibilization were given in figure 1.6.

Figure 1.6: Reactive groups commonly encountered in reactive compatibilization. [12]

14 Nakason [4] et al. has investigated the effect of different compatibilizers on the blends of rubber and High Density Polyethylene, e.g. tensile strength (Fig 1.7) and elongation at break

(Fig 1.8).

Figure 1.7: Tensile strength of thermoplastic vulcanizates of 60/40 NR/HDPE blends with various types of blend compatibilizers. [4]

Figure 1.8: Elongation of thermoplastic vulcanizates of 60/40 NR/HDPE blends with various types of blend compatibilizers. [4]

In Nakason’s literature, they show tensile strength for various Thermoplastic vulcanizates

(TPVs) based on NR/HDPE (60/40), blend without and with various types of blend compatibilizers in figure 6. It can be seen that addition of unmodified phenolic resins and modified phenolic resin caused a marginal improvement in the tensile strength. However, the addition of Liquid NR (LNR) lowered the tensile strength of TPVs. However, the addition of

15 LNR lowered the tensile strength of the TPVs. This observation does not agree with other literature. This might be attributed to a difference in the chemical environment in the present

LNR. The LNR behaved as a processing aid or a plasticizer in the blending system because a higher elongation at break was observed (Figure 1.8). In blending systems with phenolic resins (SP-1045 and HRJ-10518), the methylol groups are capable of reacting with the unsaturated sites in the NR molecules to produce a Chroman ring structure, as a consequence, the TPVs with SP-1045 and HRJ-10518 exhibit a higher tensile strength and elongation at break than those of the un-compatibilized blend. The TPVs with modified phenolic HDPE resins also exhibited a greater improvement in tensile strength and elongation at break.

I.4. Blending methods

The blending of polymers and rubbers (at a ratio of components of 90/10) was conducted in the melt state in internal-type Brabender mixer or in twin-screw Berstorff extruder

(diameter of screw D=25mm, ratio L/D=23) at different rotor (screw) rotation speeds and temperatures of 200 and 240 0C. [16]

Noyama[17] et al. blended PBT and rubber as follows: melt-mixed in the presence of adipic acid (content of adipic was 0.4 phr) at 260 0C for 15 min by using a Mini-Max molder (CSI-

183 MMX, Custom Scientific Instruments, Inc.). The blend ratio of PBT and rubber was fixed at 50/50 weight ratio.

The Ethylene Propylene Rubber (EPRs) were blended with polypropylene on a Berstorff co-rotating twin screw extruder (L/D=33, D=25mm) in the A. van der Wal[18] et al. work. A

80/20 vol% PP-EPR master blend was prepared at barrel temperature of 230 0C and a screw speed of 100rpm. During a second extrusion step, this master blend was diluted to afford blends with EPR contents of 10 respectively 5 vol%. The second extrusion step was carried out over the last quarter of the screws to minimize the change in blend morphology.

16 Conditions during the second extrusion step were identical to those during the first extrusion step.

17 II. OBJECTIVES

The scope of this thesis is to study the possibility of recycling EPDM rubber powder by blending with thermoplastic polymer using various compatibilizers. Namely:

1. Studying the non-reactive compatibilization capability of 1-octene and reactive

compatibilization of octyl phenol formaldehyde (SP-1045) and phenolic resin with

active hydroxymethyl groups (HRJ-10518).

2. Evaluating the mechanical properties and microstructures of the obtained

thermoplastic / EPDM rubber-blends.

3. Comparing different effects of thermoplastic polymer EVA copolymer and LDPE on

the mechanical properties of the blends, that is, which is the better to recycle the

EPDM rubber.

18 III. MATERIALS AND METHODS

III.1. Materials

• Recycled EPDM rubber powder was used.

• Low density polyethylene, FA3220, was provided by Borealis A/S (detailed data sheet

is listed in appendix A).

• Optene, Ethylene methylacrylate copolymer, was manufactured by Borealis, Finland

(detailed data sheet is listed in appendix B1); this kind of commodity we can buy today

is Dupont Elvaloy 1126 AC (detailed data sheet is listed in appendix B2).

• Ethylene based octene Plastomer, EXACT 0210, was manufactured by DEX-

Plastomers V.O.F, The Netherlands (detailed data sheet is listed in appendix C).

• Phenolic resins SP-1045 and HRJ-10518 were supplied by SI Group- Bethune SAS-

France (Appendix D).

• Zinc oxide extra pure was provided by Sigma-Aldrich, Germany.

• Tin chloride 98% was provided by Sigma-Aldrich, Germany.

19 III.2. Methods

III.2.1. Specimens

III.2.1.1. Raw materials preparation

30 grams of blend containing different percentage of recycled rubber, EMA or LDPE, compatibilizer and additives was used for each batch (Appendix D).

When unvulcanized rubber was used (Section IV.4), unvulcanized rubber was added first and then the recycled rubber was added in the chamber.

III.2.1.2. Specimen preparation

The mixing machine Plasti-Corder® PLE 650, Brabender was heated to 140oC and kept constant before used. The rotating speed was maintained at 70 rpm.EMA or LDPE was first introduced into the mixing chamber. When it was totally melted, compatibilizer and rubber were added consecutively. In case of reactive compatibilization, reactive compatibilizers and other chemicals (Table 1) were incorporated into the mixing chamber as the mixing schedule shown in Table 2. The blend, then, was mixed in 10 minutes and compression molded using at 150oC, 25 MPa in 5 minutes into sheets approximately 1.5 mm thick with hot pressing equipment (FW-2200 type from P.h.i Pasadena Hydraulics, Inc, USA). Finally, the resulting sheet was cooled down quickly by cold water to ambient temperature.

III.2.2. Mechanical testing procedures

III.2.2.1. Tensile strength testing

The produced sheet was cut into desired specimens under ASTM- D412-06a standard using standard dumbbell die C (Fig.3.1). Specimens, then, were mounted on Instron® 4411 tensile testing equipment between two mechanic grips. The initial distance between the two grips was 70 mm. The testing standard was ASTM-D412-06a using the load cell of 500 N and loading speed of 500 mm/min.

20 During the test, the room temperature and humidity were in the range of 210-230C and

27%-35% respectively.

Tensile data were averaged over at least five specimens.

Table 1: Compounding formulation used to prepare rubber/thermoplastics blends

Ingredient Quantity

Rubber 55 wt%- 85 wt%

EMA/LDPE 5 wt% - 15 wt%

Compatibilizer 5 wt% - 25wt%

ZnO (for reactive compatibilization only) 3 phr

SnCl2 (for reactive compatibilization only) 1.5 phr

Table 2: Mixing schedule (descending order)

Ingredient Mixing time (mins)

EMA/LDPE 1-2

Compatibilizer 1

ZnO (if used) 1

SnCl2 ( if used) 1

EPDM Rubber 10

Dimension A B C D D-E F G H L W Z

mm 25 40 115 32 13 19 14 25 33 6 13

Figure 3.1: Standard dumbbell die C for tensile strength test (ASTM-D412-06a)

Figure 3.2: Standard die T for tear strength test (ASTM-D 624-91)

22 III.2.2.2. Hardness testing

The test was carried out under ASTM-D2240 standard using durometer (hardness Shore

A). Standardized hardness-measuring equipment using a sharp needle was applied directly onto the surface of specimens to measure hardness. Data were averaged over six different positions.

III.2.2.3. Tear strength testing

Analyzed mixture was cut into required specimens according to ASTM-D 624-91 standard using standard die T (Fig.3.2). Specimens, then, were mounted on Instron® 4411 tensile testing equipment between two mechanic grips. A load cell of 500 N was used. Loading speed of 50 mm/min was maintained during the test.

Tear strength data were averaged over at least five specimens.

III.2.3. SEM analysis

Tensile, tear and cut surface of specimens were analyzed by scanning electron microscope

SEM, model JSM 6460LV from JEOL Ltd, Japan. A thin film of gold was applied on the specimen surfaces before analysis. Then, secondary electron images SEI were recorded.

Working voltage was kept at 20 kV.

III.2.4. DSC analysis

A METTLER TOLEDO DSC 821e with a TA-STARe software was used throught the study. Calibration of the instrument was done by the standard material (Indium and Zinc). The

DSC analysis was studied at the heating rate of 100C/min.

III.2.5. Compressive set testing

The test was carried out under ASTM-D 395-89 standard. Type 2 specimen (6.0 mm in thickness, 13.0 in diameter) and method B was used. Room temperature 230C and 550C was

23 investigated and the time was 72 hours. The percentage change in specimen’s thickness was, then, measured.

24 IV RESULTS AND DISCUSSION

IV.1 Non-reactive compatibilization

We studied the influence of different non-reactive compatibilizers, EVA, Kraton, MAPE and1-octene (EXACT 0210) on the tear strength of the EMA and rubber blends. The results are shown in figure 4.1.

20 18 16 14 15 12 10 8 6 10 4 Tear Strength (kN/m) Strength Tear 2

Tear strength (kN/m) strength Tear 0 5 % % % % % % A15 ACT15 EM APE15 LDPE20 +EXACT5 EX M %+EXACT5 5%+ 5 1 E1 0 P EMA15% EMA LD EMA15%+EXACT10% EMA15%+EVA10% EMA15%+Kraton10% The rest is EPDM rubber The rest is EPDM rubber Figure 4.1: Comparison of tear strength between different non-reactive compatibilizers

It can be seen form the figure that EXACT was the best compatibilizer in EPDM waste rubber/EMA compared to others. That is, in EMA15wt% + compabilizer10wt% blends,

EXACT increased the tear strength to 16.47 MPa, compared to 9.70 MPa with EVA and 9.62

MPa with Kraton, and the percentage is 70% and 71% respectively; in EMA15wt% + compatibilizer 15wt% blends, EXACT increased the tear strength 88% compared to

MAPE(18.29 Vs. 9.74 MPa). We can also see from the figure that the mechanical properties were not increased enough by just adding EXACT, EMA or LDPE. It is necessary to use thermoplastic polymer and compatibilizer to achieve the expected properties.

The compatibilization effect of EXACT on the recycled EPDM rubber/EMA was investigated in detail. The mechanical properties changes as the content of EXACT increases

(Figure 4.2 to Figure 4.6, the dashed line represents value of blue and black reference material).

25 8

3 10% EMA Tensile strength (MPa) 2 15% EMA 1 20% EMA

0 0 5 10 15 20 25 30 35 Content of EXACT (%)

The rest is EPDM rubber

Figure 4.2: Tensile strength of recycled EPDM rubber/EMA blends compatibilized by EXACT

450

400

350

300

250 10% EMA 15% EMA 200 20% EMA 150 Elongation at break (%) 100

0 0 5 10 15 20 25 30 35

Content of EXACT (%)

The rest is EPDM rubber

Figure 4.3: Elongation at break of recycled EPDM rubber/EMA blends compatibilized by EXACT

26 40

) 30 10% EMA 25 15% EMA 20% EMA 20

Young's modulus(MPa 10

0 0 5 10 15 20 25 30 35 Content of EXACT (%) The rest is EPDM rubber

Figure 4.4: Young’s Modulus of recycled EPDM rubber/EMA blends compatibilized by EXACT

10% EMA 10 15% EMA

Tear strength (%) 20% EMA

0 0 5 10 15 20 25 30 35 Content of EXACT (%) The rest is EPDM rubber

Figure 4.5: Tear strength of recycled EPDM rubber/EMA blends compatibilized by EXACT

27 90

70 10% EMA 15% EMA 65

Hardness shore A shore Hardness 20% EMA 60

50 0 5 10 15 20 25 30 35 Content of EXACT (%) The rest is EPDM rubber

Figure 4.6: Hardness of recycled EPDM rubber/EMA blends compatibilized by EXACT

It has been found during the experiment that the total amount of EMA and EXACT should be at least 15wt%; otherwise the blends can not be pressed to a plate strong enough to be tested.

It could be seen that the tensile strength and the elongation at break increased obviously as the EMA increased, and increased as the content of EXACT in the beginning and then decreased after an optimum value. The variations of Young’s modulus with the content of

EXACT are not easy to explain. In the case of 15wt% EMA, young’s modulus were improved as increased the content of EXACT was increased, and in the case of 10wt% EMA and

20wt% EMA, there exists a maximum value of the modulus as the content of EXACT increased. The tear strength was improved with increasing the concentration of compatibilizer

28 and EMA, and a small decrease was observed for 20wt% EMA blends. Finally, the hardness did not change much as the EXACT and EMA increased.

We could also see that there exist maximum values in the tensile strength and elongation at break (Figure 4.2 and Figure 4.3): 7.5wt% EXACT in the case of 10wt% EMA, 25wt%

EXACT in the case of 15wt% EMA and 15wt% EXACT in the case of 20wt% EMA. There is a critical volume of compatibilizer in each of the blend component. Nguyen [19] also found a critical value in the compatibilization of waste tire rubber/EMA blends.

This phenomenon was also investigated by other researchers [20, 21]. A possible mechanism for maximum values in tensile strength and strain at break might be the formation of a compatibilizer multilayer structure in the interphase [21]. Thus, in stead of going into a single layer at the interface, resulting in a higher volume fraction, the additional compatibilizer might simply form additional lamellae. The effective interfacial tension would then remain more or less constant. Favis et al. [20] explained that the obtained maximum values were due to the fact that dispersed phase had reached critical domain size which could be ascribed to the balance of viscous forces tending to break the dispersed drop, and interfacial tension forces tending to resist deformation and disintegration. Noolandi and co-workers [22] noted that modulus increased with the increase in compatibilizer concentration, reaching maximum at a critical volume fraction, which is sufficient to saturate the interphase surfaces. They proposed that micelle formation would be energetically favorable when the concentration of the compatibilizer became sufficiently high, thus, the concentration of compatibilizer in the interphase region could be expected to remain approximately constant, with the interfacial tension correspondingly unchanged.

29 8

7 EMA15%+EXACT5% 6 EMA15%+EXACT7,5% EMA15%+EXACT10% 5 EMA15%+EXACT12,5% EMA15%+EXACT15% 4 EMA15%+EXACT20% EMA15%+EXACT25% 3 EMA15%+EXACT30%

Stress atbreak (MPa) 2 EMA20%+EXACT5% EMA20%+EXACT10% 1 EMA20%+EXACT15% EMA20%+EXACT20% 0 REFERENCE BLACK 100 150 200 250 300 350 400 REFERENCE BLUE Elongation at break (%) The rest is EPDM rubber

Figure 4.7 : Stress-elongation relationship of recycled EPDM rubber/EMA blends compatibilized by EXACT

The analysis of stress-elongation relationship is shown in Figure 4.7. It is obviously that the blend containing 20wt% EMA and 15wt% EXACT has the best stress and elongation at break. This combination also has the best tear strength. However, its Young’s modulus was relative low. Another blend with 15wt% EMA and 25wt% EXACT had a little lower stress and elongation at break, but it has a higher Young’s Modulus and the tear strength is the same.

It is possible to select the different combination depending on the different applications.

We have tested talcum as the anti-agglomeration agent [23]. The anti-agglomeration agent could avoid the dispersed phase agglomerate during blending process in order to improve the mechanical properties of the blends. 0.3 Gram (1wt%) of talcum was added to the mixture

(70wt%EPDM rubber + 15wt%EXACT + 15wt% EMA) and the results are displayed in

Figure 4.8.

4 without talcum talcum 1% 3

stressat break (MPa) 2

0 0 50 100 150 200 250 300 350 Elongation at break (%)

PE15%+EXACT15% PE15%+EXACT15% 35 25 30 20 25 20 15 15 10 10 5 5 Tear strengthTear (kN/m) Young's Modulus (MPa) 0 0 without talcum Talcum1% without talcum Talcum1%

The rest is EPDM rubber The rest is EPDM rubber Figure 4.8: Effect of talcum on the mechanical properties of 70wt% EPDM rubber + 15wt%EXACT+ 15wt% EMA

As illustrated in Fig.4.8, talcum did not enhance the anti-agglomeration as planned. In fact, the tensile properties of the blends were decreased since adding talcum destroyed the interfacial adhesion. This conclusion is identical with another study on waste tire rubber/EMA blends carried out under the same condition by Nguyen [19], 2008.

IV.2 Reactive compatibilization Figure 4.10 shows that there exist a critical volume of compatibilizer in both SP1045 and

HRJ10518, which is the same result we could see from non-reactive compatibilizer EXACT.

31 Due to the fact that all available unsaturated sites in EPDM rubber and EMA molecules were reacted by methyl groups present in compatibilizers, the blends became less rubber like with higher young’s modulus and hardness.

There is a “cross point” (where the two lines crosses) in both tensile strength and tear strength changing as the content of reactive compatibilizers (Figure 4.10 and 4.12). When the content of compatibilizer was lower than 15wt%, the strength of the SP1045-based blends was better; the blends compatibilized by HRJ10518 had higher strength above 15wt% compatibilizer. The different results were observed by Nguyen [19]. In that study, the tire waste rubber was the raw material. Nguyen pointed out that stress at break, elongation at break and tear strength of blends compatibilized by HRJ-10518 were 10% to 50% higher than those of blends compatibilized by SP-1045.

This cross point phenomenon has the relationship with the structure of SP1045 and

HRJ10518 (Figure 4.9). Both of them are phenolic resins, SP1045 has more complex structure than HRJ10518. At low compatibilizer content, SP1045 and HRJ10518 both could react with the un-saturated bonds in the blends, and the use of SP1045 indicate that there is a higher crosslinking density compared to HRJ10518 resulting in higher strength. In Nguyen’s report,

SP1045-based blends gave a relative higher tensile strength and elongation at break when the compatibilizer is 2.5wt% (Figure4.16). At high content of compatibilizer, there might exist steric obstuction, which makes it harder for SP1045 to reach the interfacial surface and react with un-saturated sites, as a result the strength of SP1045-based blends could not increase as

HRJ10518-based ones do.

According to the supplier, HRJ10518 is a fast curing agent, further more, considerably higher tensile strength was achieved with HRJ10518-based blends, and consequently, the combination 15wt% EMA+ 25wt% HRJ10518 + 60wt% EPDM rubber was the best choice within reactive compatibilizers.

Figure 4.9: Molecular structure of reactive agents [6] A: SP-1045 B: HRJ-10518

4 SP1045

3 HRJ10518 Tensile strength (MPa) 2

0 0 5 10 15 20 25 30 35

Content of compatibilizer (%)

Figure 4.10: Tensile strength of recycled EPDM rubber/EMA blends compatibilized by reactive agent.(15wt% EMA, 4wt% additives and the rest is EPDM rubber)

33 350

300

250

200

150 SP1045 HRJ10518

Elongation at break (%) break at Elongation 100

0 0 5 10 15 20 25 30 35 Content of compatibilizer (%)

Figure 4.11: Elongation at break of recycled EPDM rubber/EMA blends compatibilized by reactive agent.(15wt% EMA, 4wt% additives and the rest is EPDM rubber)

20 SP1045 15 HRJ10518 Tear strength (kN/m) 10

0 0 5 10 15 20 25 30 35 Content of compatibilizer (%)

Figure 4.12: Tear strength of recycled EPDM rubber/EMA blends compatibilized by reactive agent.(15wt% EMA, 4wt% additives and the rest is EPDM rubber)

34 120

100

40 SP1045 Young's Modulus (MPa) HRJ10518 20

0 0 5 10 15 20 25 30 35

Content of compatibilizers (%)

Figure 4.13: Young’s Modulus of recycled EPDM rubber/EMA blends compatibilized by reactive agent.(15wt% EMA, 4wt% additives and the rest is EPDM rubber)

100

SP1045 70 HRJ10518 Hardness shore A

50 0 5 10 15 20 25 30 35 Content of compatibilizer (%)

Figure 4.14: Hardness of recycled EPDM rubber/EMA blends compatibilized by reactive agent.(15wt% EMA, 4wt% additives and the rest is EPDM rubber)

35 12 190 SP-1045 )

SP-1045 % HRJ-10518

( 170 HRJ-10518 pa) 10 150 eak M r ( b

t 130 a eak

8 n 110 br o i

at 90 s s ongat e 6 70 l r t E S 50 4 2,5 5 7,5 10 2,5 5 7,5 10 Compatibilizer percentage Compatibilizer percentage

Figure 4.15: Mechanical properties of recycled tired rubber/EMA blends compatibilized by reactive agents. (15wt% EMA and the rest is rubber) (From Nguyen[4], 2008)

We chose the combinations: 65wt%EPDM + 20wt%EMA +15wt%EXACT and 60wt%

EPDM+ 15wt%EMA + 25wt% HRJ10518 for non-reactive and reactive compatibilizer respectively. Considering these two combinations with quite high composition of compatibilizer: 15wt%EXACT and 25wt%HRJ10518, we deduced that there maybe exist three phase in the blends, which probably was the reason that the mechanical properties were not so elevated especially the tensile strength. Therefore, author investigated the properties of the combinations with higher content of EMA and lower content of compatibilizer. The results with 35wt% EMA and 5wt% compatibilizer are displayed in figure 4.16. The new compatibilizer PhHRJ-PE was phenolic modified polyethylene, which is the best compatibilizer with high tensile strength and elongation at break in the literature [4].

With 35wt% EMA and 5wt% compatibilier blends, see figure 4.16; HRJ10518 gave the best tensile strength and tear strength compared to EXACT and PhHRJ-PE. The tensile strength is even a little higher than the blend EMA 15wt% + HRJ 25wt%. The elongation of

35wt% EMA + 5wt% compatibilier blends are considerably higher than the blend EMA

15wt% + HRJ 25wt%, and the HRJ5wt%-based blends had the highest one. Figure 4.16

36 shows that the blends with low compatibilizer content had lower young’s modulus and relative lower hardness, which means the low content of compatibilizer blends were more rubber-like elastomers. Considering we need high tensile strength, it is clear that the combination 35wt%EMA+ 5wt%HRJ is the best choice within low compatibilizer content.

8 600

7 500 )

6 % ( 400 5

4 300

3 ation at break break at ation

g 200 2 Tensile strength (MPa) strength Tensile Elon 100 1

0 0 EMA15%+HRJ25% EMA35%+EXACT5% EMA35%+HRJ5% EMA35%+PhHRJ-PE5% EMA15%+HRJ25% EMA35%+EXACT5% EMA35%+HRJ5% EMA35%+PhHRJ-PE5% The rest is EPDM rubber The rest is EPDM rubber

100 30 90 25 ) 80 )

MPa 70 ( 20 kN/m 60 ( th

50 g 15 40 's M o d u lu s

g 10 30 Tear stren

Youn 20 5 10 0 0 EMA15%+HRJ25% EMA35%+EXACT5% EMA35%+HRJ5% EMA35%+PhHRJ-PE5% EMA15%+HRJ25% EMA35%+EXACT5% EMA35%+HRJ5% EMA35%+PhHRJ-PE5%

The rest is EPDM rubber The rest is EPDM rubber

100 90 80 70 60 50 40 30 Hardness shoreA 20 10 0 EMA15%+HRJ25% EMA35%+EXACT5% EMA35%+HRJ5% EMA35%+PhHRJ-PE5%

The rest is EPDM rubber

Figure 4.16: Comparison of mechanical properties of recycled EPDM rubber / EMA blends

( The blends with reactive compatibilizers contain 4wt% additives)

IV.3 Effect of pressing pressure during plate production The compression pressure 25MPa was constant in the above analysis. Effect of pressure on the mechanical properties of recycled EPDM rubber/EMA blends was also studied. The values were shown in figure 4.17. We could see that there were not remarkable difference of the mechanical properties depend on the increasing pressure except that an elevation of tensile strength with HRJ10518-based blends. The elevation might due to the system error, plus the standard deviation of the point is quite large, that is, the elevation could be ignored when the process was replaced by extrusion. Thus, the compression pressure did not have much influence on the mechanical properties of the recycled EPDM rubber/ EMA blends. This result was also carried out bye Nguyen with tire rubber/EMA blends [19].

8 450

400 7

350 6 300 5 250 4 200

150 3 EMA15%+EXACT25%

Elongation break (%) at 100 EMA15%+EXACT25% EMA15%+HRJ20%

Tensile strength (MPa) strength Tensile 2 EMA15%+HRJ20% 50 1 0 2,5 6,25 12,5 25 0 2,5 6,25 12,5 25 Pressure (MPa) Pressure (MPa) The rest is EPDM rubber The rest is EPDM rubber

90 25

80 20 70

60 15 50 EMA15%+EXACT25% 40 10 EMA15%+HRJ20% 30 Tear strength (kN/m)

Young's Modulus (MPa) 20 EMA15%+EXACT25% 5 10 EMA15%+HRJ20%

0 0 2,5 6,25 12,5 25 2,5 6,25 12,5 25 Pressure (MPa) Pressure (MPa) The rest is EPDM rubber The rest is EPDM rubber

38 The rest is EPDM rubber

100

50 EMA15%+EXACT25% EMA15%+HRJ20% 40

Hardness shoreA 30

0 2,5 6,25 12,5 25 Pressure (MPa)

Figure 4.17: Effect of pressure on the mechanical properties of recycled EPDM rubber/EMA blends

IV.4 Effect of unvulcanized rubber In order to study the effect of unvulcanized rubber on the tear strength of the blends, some amount of unvulcanized rubber (1 part per 9 parts of the recycled EPDM rubber) was added to the mixture. The results are shown in figure 4.18.

At the same blending temperature 1400C, the tear strength did not change much with adding the unvulcanized rubber. As the temperature increases, EXACT-based blends and high

HRJ10518 content-based blend just cause minor change in tear strength. In the case of low

HRJ10518 content-based blend increases at 1650C and 1800C.

Loo [25] studied the physical properties of natural rubber with different vulcanization temperature 140-200 0C, noted that high vulcanization temperatures (for example 180-200 0C) produce vulcanizates with inferior physical properties and pointed out that less than 1 site of scission per 100 crosslinked isoprene units was established in the temperature range of 140-

200 0C. In another paper [26], loo pointed out the possibility of the crosslink destruction at elevated cure temperature. Mukhopadhyay and De [27] deduced that the deterioration in

39 properties at high cure temperature was attributed to lower state of crosslinking and changed in the vulcanizate structure.

We could see from the DSC analysis of unvulcanized rubber (figure4.19) that the start of the vulcanizing is at 1600C, the vulcanizing peak is at 1900C and full vulcanization is at 2100C.

With low content of HRJ10518, at 1650C, the increasing rubber-rubber linkage was dominant, compared to the worse rubber-EMA compatibility caused by interfacial surface deterioration at higher temperature, as a result, the tear strength increased; at 1800C, the exothermal heat of vulcanization was much higher, thus the increasing rubber-rubber linkage would be quite higher, however, the tear strength was not elevated, that is because the lower rubber-EMA compatibility caused by the higher temperature. The tear strength of the high HRJ10518 content-based and EXACT-based blends did not change due to the high content of compatibilizer. As a conclusion, this results show that a low content of compatibilizer with the addition of unvulcanized is preferred concerning the tear strength.

EMA 15%+EXACT 25% 30 EMA 15%+HRJ 20% EMA 35%+HRJ 5% 25

10 Tear strength (kN/m)

0 10/0 @ 140◦C 9/1 @ 140◦C 9/1 @ 165◦C 9/1 @ 180◦C Used rubber/unvulcanized rubber

Figure 4.18: Effect of unvulcanized rubber and blending temperature on tear strength of recycled EPDM rubber/EMA blends.

Figure 4.19: DSC analysis of unvulcanized rubber, scanning rate 10 0C /min.

IV.5 Microstructure analysis Tensile and tear surfaces of various recycled EPDM rubber/ EMA blends were studied by the use of scanning electron microscopy (SEM). Both reactive and non-reactive compatibilizers used in this study give homogeneous microstructures (Fig.4.20). However,

EXACT based blends show more plastic deformation of the matrix than the blends compatibilized by reactive agents.

It is also observed that there is a good connection between the dispersed phase and the matrix established by employing compatibilizers (Fig.4.21)

A. Fracture surface of 20wt%EMA+15wt%EXACT

B. Fracture surface of 15wt%EMA+25wt%SP C. Fracture surface of 5wt%EMA+25wt%HRJ Figure 4.20: SEM images of recycled EPDM rubber/EMA blends

A.EXACT0210

42 B. SP1045 C. HRJ10518 Figure 4.21: Phase connection of recycled EPDM rubber/EMA blends

IV.6 Comparison of the properties between LDPE/EPDM and EMA/EPDM blends

A study of the properties of LDPE/recycled EPDM rubber blends, EMA /recycled EPDM rubber blends were performed, the results are shown in Figure 22-24.

In figure 22, we can see the Comparison of the properties of the blends with recycled

EPDM rubber and LDPE or EMA compatibilized by EXACT. As the content of EXACT increased, elongation at break and tensile strength were improved in both LDPE and EMA blends, but in all the blends that were investigated, the tensile strength and elongation at break of the EMA blends are higher than in the LDPE blends. Since the tensile strength of LDPE

(25MPa) is higher than EMA (OPTENE 15MPa), it is indicated that the effect of the use of

EXACT as a compatibilizer is more effective in the case of EMA/EPDM blends. LDPE based blends have a much higher Young’s modulus compared to EMA based blends, as shown in figure 4.22. While the tear strength of the LDPE based blends was much higher than EMA based blends at high EXACT content. LDPE based blends could be selected when high tear strength and stiffness are acquired. Since the stiffness of LDPE based blends was clearly higher, the hardness should be higher, that was proved in Figure 4.22.

400 8

350 7

300 6

250 5

200 4

150 3 Elongation at break (%) break Elongationat Tensile strength (MPa) strength Tensile EMA15% 100 2 LDPE15%

50 EMA15% 1 LDPE15% 0 0 EXACT5% EXACT15% EXACT25% EXACT5% EXACT15% EXACT25%

70 35

60 30

50 25 EMA15% 40 LDPE15% 20

30 15 EMA15%

Tear strength (kN/m) LDPE15%

Young's Modulus (MPa) Modulus Young's 20 10

10 5

0 0 E XA CT5% E XA CT15% E XA CT25% EXACT5% EXACT15% EXACT25%

100

40 Hardness shore A 30 EMA15% 20 LDPE15% 10

0 EXACT5% EXACT15% EXACT25%

Figure 4.22: Mechanical properties of the blends: EMA/EPDM/EXACT and LDPE/EPDM/EXACT

The properties of the blends with recycled EPDM rubber and LDPE or EMA using HRJ as compatibilizer were shown in figure 4.23. The tensile stress of LDPE based blends have the same tendency as EMA based blends with increasing amount of HRJ, while the elongation at break and tear strength of LDPE based blends were decreased by adding more reactive

44 compatibilizer HRJ. At high the content of HRJ, the Young’s modulus of this kinds of blends were too high compared to the rubber like material. In the future work there should be focus on the lower content of HRJ concerning LDPE based blends. The hardness of the two kinds of blends did not change much as increasing the content of HRJ.

350 8

300 7

6 250

5 200 4 150 3

100 Tensile strength (MPa) Elongation (MPa) break at 2 EMA15% EMA15% 50 LDPE15% 1 LDPE15%

0 0 HRJ 5% HRJ 15% HRJ 25% HRJ 5% HRJ 15% HRJ 25%

250 30

25 200 EMA15% EMA15% LDPE15% LDPE15% 20

150 15

100 10 Tear strength (MPa) Young's Modulus(MPa)

50 5

0 0 HRJ 5% HRJ 15% HRJ 25% HRJ 5% HRJ 15% HRJ 25%

100

40 Hardness shore A shore Hardness 30

20 EMA15% LDPE15% 10

0 HRJ 5% HRJ 15% HRJ 25%

Figure 4.23: Mechanical properties of the blends: EMA/EPDM/DRM and LDPE/EPDM/HRJ

45 500 8 450 7

) 400 6 350

eak (% 5 300 250 4 200 3 150 2

Elongation at br 100 Tensile strength (MPa) Tensile strength 1 50 0 0

% % % % % 5 5 5 5 5 15% 5% 1 1 J J T T J C R R CT HRJ C H H A A + A X X + XACT15% %+ E % % EX E %+HR + E 5 5 5 + 3 3 35 % % A E %+ E 0 0 P 0 P 2 2 M D 2 MA3 D A E E L E L M P E D DPE20%+ L EMA L

The rest is EPDM rubber The rest is EPDM rubber

120 25

100 20

80 15

60 10 40

Tear strength (kN/m) strength Tear 5 Young's20 Modulus (MPa)

0 0 % % 15 5% 5 RJ5% H RJ HRJ H + %+ +EXACT 35 +EXACT15% 5% % A % A3 EM LDPE35%+ EM LDPE35%+HRJ5% EMA20%+EXACT15% EMA20 LDPE20 LDPE20%+EXACT15% The rest is EPDM rubber The rest is EPDM rubber

100 90 80 70 60 50 40 30 Hardness shore A 20 10 0

% % % 5 5 5 T1 T15% RJ C RJ H AC H EX 5%+ 5%+ 3 %+ 3 0 DPE EMA L MA2 DPE20%+EXA E L The rest is EPDM rubber Figure 4.24: Mechanical properties of the blends: EMA/EPDM and LDPE/EPDM ( the blends with HRJ contain 4wt% additives)

46 A

90 78,175 80 68,860 ) 70 60 50 40 30 23,245 21,789

Compresstion set (% 20 10 0

% 5 1 T

Blue reference material Black reference material

65%+LDPE20%+EXACT15% M

EPDM65%+EMA20%+EXAC EPD

80 72,656 70 63,759 ) 60

40 33,771 33,496 30

20 Compresstion (% set 10

l ia ial % % 15 mater ACT ce EX ren rence mater e fe %+ ref e 20 ck ue r PE Bl Bla LD 5%+ 6 M D EPDM65%+EMA20%+EXACT15 EP

Figure 4.25: Comparison of compression set under different temperature: A 55 0C B Room

temperature 23 0C

47 We chose the two best combinations: 20wt% thermoplastics + 15wt%EXACT and 35wt% thermoplastics + 5wt% HRJ. The thermoplastics are LDPE and EMA, see figure 4.24. We could see that the tensile strength, and the tear strength of the LDPE based blends are less compared to EMA based blends, the hardness is a little higher. However, compared to EMA based blends, the elongation at break is much lower while the Young’s modulus is much higher, compared to the reference material. The problems of LDPE based blends are to increase the elongation at break and to decrease the stiffness.

Comparison of compression set is shown in figure 4.25. Both EMA and LDPE based blends have higher compression set compared to the reference material at 55 0C and room temperature. Sutanto and co-workers [28] pointed out that the higher compression set of the revulcanizate was the consequence of its lower crosslink density compared to that of the virgin rubber. Except for the lower crosslink density caused by processing, the adding of thermoplastics LDPE and EMA was also the reason due to the higher compression set. LDPE based blends contributed to a lower compression set than EMA based blends, about 10%.

48 V. CONCLUSIONS

• EXACT 0210 is a more appropriate non-reactive compatibilizer than EVA and Kraton-

• The total weight of thermoplastic and compatibilizer should be higher than 15wt% to

achieve a blend strong enough to be test.

• A critical volume of compatibilizer for each type of compatibilizer. In the case of

15wt% EMA /EPDM blends, it was 25 wt% in reactive and non-reactive compatibilizer,

respectively.

• EXACT 0210 would be a good choice if high elongation at break is desired and reactive

compatibilizers will be selected when high stiffness is needed.

• HRJ-10518 is better than SP-1045 in terms of compatibilizing capabilities because of

the structure of their molecular structure. SP-1045 possessed a more complex structure

with ether group in molecule while HRJ-10518 did not. It was, thus, easier for HRJ-

10518 to reach interfacial surface and react with un-saturated sites at high content.

• Talcum did not enhance the anti-agglomeration. In fact, talcum destroyed the interfacial

surface causing deterioration in tensile properties of the blends.

• Pressing pressure during the production of the test samples can be minimized without

any adverse effect on mechanical properties of recycled EPDM rubber and EMA blends

• Recycled rubber mixed with non-vulcanized rubber and incorporated into the mixing

chamber at vulcanizing temperature; With low content of HRJ10518, at 1650C, the

increasing rubber-rubber linkage was dominant, the tear strength increased. At 1800C,

the tear strength was not increased due to the worse compatibility of rubber-EMA at the

49 higher temperature. On the other hand, the tear strength of the high HRJ10518 content-

based blend and high EXACT content based blend did not change because the

compatibilization reached the equilibrium with unvulcanized rubber and higher

temperature.

• Both reactive and non-reactive compatibilizers gave homogeneous microstructures.

• EXACT containing blends show more plastic deformation of the matrix than the blends

compatibilized by reactive agents.

• Good connection between the dispersed phase and the matrix was established by

employing compatibilizers according to SEM investigation.

• Tensile strength, tear strength of the LDPE based blends are less, the hardness is higher,

the elongation at break is much lower and the Young’s modulus is much higher than the

EMA based blends.

• Compression set of the blends containing the recycled EPDM rubber/EMA and the

recycled EPDM rubber/LDPE is high compared to the reference materials.

50 VI. FUTURE WORK

• Studies on the blends of recycled EPDM rubber and LDPE should be carried out in

detail; especially it should be concentrated on reducing the stiffness and increasing

elongation at break of the blends by changing blend ratio, amount and the kinds of

compatibilizer.

• Instead of EMA and LDPE, the investigation on recycled EPDM rubber with PP, PA

and EBA using appropriate compatibilizer should be pay attention to.

• Vulcanized properties of the blends should be studied by DSC or rheometer [24].

• The melt index of EXACT used in this thesis is 10 dg/min, while the EXACT with melt

index 1 has better tensile strength (35MPa compared to 17MPa), so EXACT 0201 or

EXACT8201 should be studied in order to increase the mechanical properties.

• Agglomeration occurs with the process of forming TPEs. Appropriate anti-

agglomeration agent(s) should be studied and applied to the blends to improve the

mechanical properties.

• Compression set represented the elastic recovery ability of the rubber, so to reduce the

value is very necessary to make the blends rubber like.

51 VII. REFERENCES

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52 11. Yan Li, Yong Zhang, Yinxi Zhang, Morphology and mechanical properties of HDPE/SRP/elastomer composites: effect of elastomerpolarity, Polymer Testing 2004, 23: 83-90

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master thesis 2008, Luleå

53 20. B. D. Favis, Polymer Communications: Phase size/interface relationships in polymer

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54 29. An Introduction to Rubber Technology, By: Ciesielski, Andrew, 1999 Rapra

55 Appendix A1. Low density polyethylene data sheet

56 Appendix A2. EMA copolymer data sheet

58 Appendix B. EXACT 0210 data sheet

59 Appendix C. SP-1045 & HRJ -10518 data sheet

61 Appendix D. SAMPLE LIST (wt%) EXACT HRJ- ADDITIVE ID Rubber EMA SP-1045 0210 10518 S 1 85.0 10 5 0 0 0

2 82.5 10 7.5 0 0 0

3 80.0 10 10 0 0 0

4 77.5 10 12.5 0 0 0

5 75.0 10 15 0 0 0

6 80.0 15 5 0 0 0

7 77.5 15 7.5 0 0 0

8 75.0 15 10 0 0 0

9 72.5 15 12.5 0 0 0

10 70.0 15 15 0 0 0

11 65.0 15 20 0 0 0

12 60.0 15 25 0 0 0

13 55.0 15 30 0 0 0

14 75.0 20 5 0 0 0

15 70.0 20 10 0 0 0

16 65.0 20 15 0 0 0

17 60.0 20 20 0 0 0

18 76.0 15 0 0 5 4

19 73.5 15 0 0 7.5 4

20 71.0 15 0 0 10 4

21 68.5 15 0 0 12.5 4

22 66.0 15 0 0 15 4

23 61.0 15 0 0 20 4

24 56.0 15 0 0 25 4

25 51.0 15 0 0 30 4

26 76.0 15 0 5 0 4

27 73.5 15 0 7.5 0 4

28 71.0 15 0 10 0 4

29 68.5 15 0 12.5 0 4

30 66.0 15 0 15 0 4

31 61.0 15 0 20 0 4

32 56.0 15 0 25 0 4

33 51.0 15 0 30 0 5

EXACT HRJ- ADDITIVE ID Rubber LDPE 0210 SP-1045 10518 S

34 80 15 5 0 0 0

35 70 15 15 0 0 0

36 60 15 25 0 0 0

37 76 15 0 5 4

38 66 15 0 15 4

39 56 15 0 25 4

40 65.0 20 15 0 0 0

41 56 35 0 0 5 4

63 Appendix E. Price Index list of materials (reference value only)

Material Price Index

Low density polyethylene 1

Ethylene and Methyl Acrylate copolymer 3.2

Kraton G 5.4-5.9

EXACT-0210 1.6

HRJ-10518 6.6

SP-1045 5.5

The Price of Low density polyethylene: 1180USD/ ton, June-November, 2008.