Based on PP and Recycled EPDM

| DOI: 10.3933/APPLRHEOL-26-33503 | WWW.APPLIEDRHEOLOGY.ORG

Rheological Characterization of Thermoplastic Elastomers (TPE) Based on PP and Recycled EPDM

Paridokht Mahallati 1, Hojjat Mahi Hassanabadi 2, Manfred Wilhelm 3, Denis Rodrigue 1

1Department of Chemical Engineering and CERMA, Université Laval, 1065 Avenue de la Médecine, Quebec, G1V 0A6, Canada 2CRIQ, 333 rue Franquet, Quebec, G1P 4C7, Canada 3Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstrasse 18, Karlsruhe, 76131, Germany

*Corresponding author: [email protected]

Received: 12.2.2016, Final version: 28.4.2016

Abstract: The rheological behavior of thermoplastic elastomers (TPE) based on 50/50 recycled ethylenepropylene-diene monomer (r-EPDM)/polypropylene (PP) was studied to determine the effect of feeding strategy when preparing these blends using twin-screw extrusion. In particular, small and large deformation characterizations have been performed to better understand the relationships between sample preparation and final properties of the blends. It was found that small changes in blend morphology (particle size and interfacial adhesion) are better distinguished in rheological properties (melt state) under large deformation (LAOS and step shear) compared to small deformation (SAOS).

Key words: Polypropylene, recycled EPDM, thermoplastic elastomers, large deformation.

1 INTRODUCTION ods have been developed to modify PP toughness such as blending with elastomers leading to the develop - Thermoplastic elastomers (TPE) are polymer blends ment of TPE based on PP and ethylene-propylene-diene that can be processed at high temperature like thermo - monomer (EPDM). These blends have been very suc - plastics (melt processing), but have mechanical prop - cessful due to structural compatibility between both erties similar to elastomers (high elasticity) at low tem - polymers and several investigations have been pub - perature. Depending on the polymers and processing lished dealing with their morphology and mechanical methods used, different families of TPE can be pro - properties [1, 4 – 10]. Due to the growing importance of duced [1]. TPE prepared by physical melt mixing of a TPE, melt rheology of thermoplastic blends was pro - polyolefin with an elastomer gained considerable at - posed as a tool to understand the relationships be - tention because their macroscopic mechanical proper - tween structural properties (morphology), processabil - ties (impact strength, elongation at break) can be mod - ity, and mechanical behavior. Therefore, the rheological ified over a wide range by simple control of composition properties of TPE have been extensively studied, but [1 – 3]. Today, polypropylene (PP) is one of the main poly - mostly under small deformation in oscillatory shear as mer used as the matrix because of its low density, bal - these measurements correlate linear mechanical data anced mechanical properties, and processing behavior. with processing in the non-linear regime [2, 3, 7, 11 – 14]. It is also easy to modify (molecular weight distribution, Over the last decade several attempts to use recy - branching, tacticity, copolymer, etc.) to meet the re - cled rubber in TPE formulations were investigated be- quirements for several applications in terms of general cause of environmental concerns and cost reduction performances [4]. Consequently, PP is widely used in [15 – 23]. Although the mechanical properties of PP/re - automobile, household appliance, and construction in - cycled EPDM (r-EPDM) blends are well-known, very little dustry. Nevertheless, the use of PP alone is restricted attention has been paid to their rheological behavior in due to its brittleness (low impact strength), especially the melt state [24]. This information is highly important at low temperature. In the last decades, several meth - to understand their processing and relate morphology

© Appl. Rheol. 26 (2016) 33503 | DOI: 10.3933/ApplRheol-26-33503 | 1 | Figure 1: Typical morphology of the samples studied: P-E (left) and E-P (right). to macroscopic properties. From our previous works on ity, and interfacial adhesion. To this end, small and large PP/r-EPDM blends [18, 19], it was found that coupling deformation characterizations were performed to get a agent addition is not necessary for this system due to complete understanding of the differences ob served in good interaction between both phases as confirmed by mechanical properties by other means than morpholog - mechanical and morphological analyses. This was ob- ical analysis (optical, scanning electron, and transmis - tained through optimization of the processing condi - sion microscopy) which is very tedious. In particular, tions (flow rate, screw speed, temperature profile, screw nonlinear oscillatory and large deformation have been design, etc.) and feeding strategy in a twin-screw ex- recently used to study the behavior of different materi - truder. It was found that the optimum properties were als like silica (SiO 2) suspensions [25], bituminous binders obtained when r-EPDM was introduced in zone 1, while [26] and polypropylene/multiwall carbon nanotube PP was introduced in zone 4 of a twin-screw extruder (MWCNT) composites [27]. having a total of 10 zones. In this case, feeding the r- EPDM first led to smaller rubber particles (around 200 μm) and higher elongation at break (155 %) compared to 2 EXPERIMENTAL the reverse case of feeding the PP first (300 μm and 86 % elongation at break). 2.1 MATERIALS In order to differentiate between the processing conditions tested, it is proposed to use rheological mea - Polypropylene (PP) and recycled ethylene-propylene-di - surements in the melt state instead of the usual me - ene monomer (r-EPDM) rubber were used in this work. chanical properties in the solid state (tension, flexion, The polypropylene (melt flow rate = 2.80 g/10 min impact, etc.). It is expected that the matrix contribution (230 °C and 2.16 kg), melt temperature = 160 °C and den - is less important in the melt state leading to a higher sity = 0.9 g/cm 3) was supplied by LyondellBasell (USA) contribution (higher sensitivity) of the blend morphol - under the trade name of Montell PF814. The r-EPDM (av - ogy in terms of the dispersed phase size, dispersion qual - erage initial particle size = 480 μm and density = 1.29 g/cm 3) was supplied by Royal Mat Inc. (Canada). More information on the materials, methods, and char - acterizations (morphological and mechanical proper - Sample code Main fee d (zone 1) Side fee d (zone 4) PP PP – ties) can be found elsewhere [18, 19]. P-E PP r- EPDM E-P r- EPDM PP 2.2 BLEND PREPARATION

Table 1: Sample codes and feeding sequences used for sample PP/r-EPDM (50/50) blends were produced in a co-rotat - produced via twin-screw extrusion. The blends are 50/50 % wt. ing twin-screw extruder (Leistritz ZSE-27, Germany) with a screw diameter of 27 mm and a L/D ratio of 40

Tensil e Tensil e Elonga tion a t Flexural Charpy impact (total of 10 zones). The extruder was operated with a Sample modu lus stre ngth bre ak modu lus stre ngth flat temperature profile of 180 °C (all the zones) at 150 (MPa) (MPa) (%) (MPa) (J/m) PP 412 ± 22 32.3 ± 0.4 792 ± 117 1500 ± 170 38 ± 4 rpm with a flow rate of 6 kg/h and a 3 mm circular die. P-E 149 ± 9 15.8 ± 0.4 85 ± 12 687 ± 9 76 ± 7 E-P 147 ± 2 14.5 ± 0.5 154 ± 13 559 ± 12 162 ± 13 The main feed hopper was at the beginning of the ex - truder (zone 1) and a secondary feeder (side-stuffer) was Table 2: Mechanical properties of the samples presented in placed at zone 4. An injection molding machine (Nissei Table 1. The blends are 50/50 % wt. PS60E9ASE, Japan) was used with a linear screw tem -

© Appl. Rheol. 26 (2016) 33503 | DOI: 10.3933/ApplRheol-26-33503 | 2 | Figure 2: Storage G' and loss G" moduli of the samples at Figure 3: Absolute value of the complex shear viscosity for the 180°C. samples at 180°C. perature profile between 180 and 200 °C from the rear to the injection nozzle with a mold temperature of 30 °C. More details on sample preparation and charac - terization can be found elsewhere [18]. Two feeding se - quences were selected as reported in Table 1. In all cases, 25 mm diameter discs were cut from the molded sam - ples for the rheological characterizations. For a base of comparison, Figure 1 presents typical micrographs of the blends, while Table 2 reports on the mechanical properties.

2.3 RHEOLOGICAL CHARACTERIZATION

Transient rheological tests (step shear) were performed on a strain-controlled TA Instruments rheometer (ARES) under a nitrogen atmosphere. All the measurements Figure 4: Polypropylene strain sweep tests at different tem - were done with a parallel plate geometry (25 mm in di - peratures ( w = 1 rad/s). ameter) with different shear rates (0.01, 0.03, 0.1, 0.3, 0.6, and 1 s -1 ) at 180 °C. Strain sweep tests were done at different temperatures (180, 200, and 220 °C) with a fre - shows that increasing temperature increases wc indi - quency of 1 rad/s between 1 and 200 % strain amplitude. cating shorter relaxation time for all the samples. Ad - Small amplitude oscillatory shear (SAOS) were done at ditionally, wc values for PP samples are higher than PP/r- different temperatures (180, 200, and 220 °C) in the fre - EPDM blends at the same temperature. For both blends, quency range of 0.05 – 400 rad/s at a controlled strain the values of wc (measured at small deformation) are amplitude of 5 % (linear viscoelastic regime). Large am - similar over the temperature range and Table 4 pre - plitude oscillatory shear (LAOS) tests were performed sents the temperature shift factors aT for a reference on a TA Instruments (ARES G2) in a strain-controlled temperature of 180°C [30]. It is clear that the addition mode by conducting experiments at different frequen - of r-EPDM into PP decreases the aT values indicating cies and 180 °C. The obtained stress was then converted that the blends are more sensitive to temperature than from a time to a frequency domain using FT-rheology the neat matrix, but the values are different for both (Fourier-Transform rheology). More details can be ob - systems indicating an effect of sample preparation tained elsewhere [28, 29]. (morphology difference). Since blend processing is per - formed in the melt state, both viscosity and elasticity (moduli) are important parameters to control. Figure 2 3 RESULTS AND DISCUSSION shows the shear storage G’ and loss G” moduli of the different samples at 180 °C under small deformation. First, small amplitude oscillatory data are analyzed to The G’ and G” values for PP/r-EPDM blends are higher obtain the cross-over frequency wc where G’ = G” , and than PP due to the presence of the dispersed phase and the elastic limit ge which represents the deformation the presence of an interface between both phases. On where the linear behavior ends, for PP and PP/r-EPDM the other hand, there is no significant differences be - at different temperatures (180, 200, and 220 °C). Table 3 tween the G’ and G” curves for both TPE blends. As pre -

© Appl. Rheol. 26 (2016) 33503 | DOI: 10.3933/ApplRheol-26-33503 | 3 | Figure 5: Strain sweep tests at 180°C for the different samples Figure 6: Stress-time curves for PP at different shear rates and (w = 1 rad/s). 180°C.

Figure 7: Stress-time curves for P-E at different shear rates Figure 8: Stress-time curves for E-P at different shear rates and 180°C. and 180°C. sented in Figure 3, the absolute value of the complex r-EPDM contribution. As reported in our previous study viscosity | h*| at 180 °C gives similar trends. It is clear that [18], feeding the r-EPDM before PP in the extruder pro - |h*| increased with r-EPDM addition since the recycled duced smaller particle sizes which also improved the rubber particles are partially crosslinked. adhesion between the matrix and the dispersed phase Figure 4 (strain sweep tests) shows the shear mod - leading to larger interfacial area. Comparing the results uli ( G’ and G” ) for PP at different temperatures, while of Figures 7 and 8, different behaviors between both the values at 180 °C for the different samples are shown blends can be seen, especially when the shear rate is in Figure 5. It is observed that G’ and G’’ values for PP/r- higher than 0.1 s -1 : P-E samples (Figure 7) have a behav - EPDM blends are higher than PP over the whole fre - ior similar to neat PP, while E-P samples have a two-step quency range because of higher interaction between deformation behavior where the second step occurs on - both phases. Nevertheless, the values of the elastic lim - ly when the shear rate is above 0.1 s -1 . In all cases, the its ge of the blends (Table 3) indicate that a difference corresponding critical total deformation (shear rate exists between small and large deformation behaviors multiply by the time) is about 3.5 and constant critical as reported by Filipe et al. [31]. Another way to apply dif - deformation for the overshoot, independent of the ferent deformation on a sample is via stress-time shear rate applied, has been reported before [32, 33]. curves (shear step) and the results for PP and PP/r-EPDM These trends point again to large deformation being samples at different shear rates (180 °C) are presented more sensitive than small deformation to small differ - in Figures 6 to 8. At low shear rates, the stress curves ence in morphology (particle size here) between both did not show any overshoots, while at higher shear samples. rates (above 0.6 s -1 ) all the samples had an overshoot To better quantify the differences between both before reaching a steady state. Again, the stress values TPE samples at high deformation, LAOS was performed for PP/r-EPDM blends are higher than neat PP due to to detect any increased nonlinearity by the incorpora -

© Appl. Rheol. 26 (2016) 33503 | DOI: 10.3933/ApplRheol-26-33503 | 4 | Figure 9: I3/1 as a function of strain amplitude for the sam - Figure 10: I3/1 as a function of strain amplitude for the sam - ples at 0.5 Hz. ples at 1 Hz. tion of r-EPDM particles into the PP matrix [29, 34]. The 4 CONCLUSIONS response was analyzed by FT-rheology which is a very reliable technique for nonlinear stress data analysis The rheological properties of a polymer blend in the melt [35]. It has been shown that the relative intensity of the state are controlling the final structure of these blends third harmonic to its first one I3/1 from FT-rheology and therefore controlling their processability and per for- quantifies the transition from the linear to nonlinear mance. Since most polymer processing methods are per- response [33]. The values of I3/1 can also be used to com - formed at high shear rate/deformation, it is important to pare different samples and the trends can indicate mor - determine the rheological behavior of the systems under phological differences in multiphase systems [36, 37]. similar non-linear conditions. Consequently, the rheolog - For our samples, the values of I3/1 as a function of strain ical behavior must be investigated over a wide range of amplitude at different excitation frequency (0.5 and deformation, frequency, and temperature. In this work, 1 Hz) are presented in Figures 9 and 10. According to the rheological behavior of PP and PP/r-EPDM blends was these curves, not only blending PP with recycled rub - studied. Using rheological characterizations under small bers increased the nonlinearity of the system (higher and large deformation, significant differences were ob - I3/1 values for P-E and E-P blends), but also different served for TPE blends having similar composition (50/50), trends in the curves were obtained. For P-E samples, a but processed differently (component feeding order in a broad peak around g = 1 is usually related to the inter - twinscrew extruder) leading to small changes in their fi - face deformation created between both phases in a nal morphology. Although their small deformation be - mul ti component system. This bump seems to increase havior was similar (SAOS), significant differences were in intensity with increasing frequency (comparison be- observed under large deformation (step shear tests and tween Figures 9 and 10). As P-E samples have larger par - LAOS combined with FT-rheology in the non-linear ticle sizes and lower adhesion with the matrix (lower regime). These differences were not only attributed to mechanical properties) [18], this bump can be associat - small differences in the dispersed phase particle size, but ed with lower compatibility between the phases in the also to the interaction level (compatibility) between both blends indicating that LAOS combined with FT-rheolo - phases. Even if small differences were observed in the sol - gy is a powerful tool to differentiate between samples id state [18], melt rheology was more sensitive to these having similar rheological behavior at small deforma - differences. This is especially the case under large defor - tion. As this is a first step, further investigations are mation as LAOS is more sensitive to particle size/geom - needed in the future. etry, while step shear is more sensitive is more sensitive to interfacial interactions [31]. Nevertheless, more work needs to be done to completely understand the relation - Sample (°C) wc (rad/s) ge (%) PP (180 ) 12 74 ships between all the parameters involved and the char - PP (200 ) 23 76 acterization performed, as well as to get simple models PP (220 ) 46 86 P-E (180 ) 6.3 8.1 for process design, control, and optimization [38]. P-E (200 ) 9.4 6.1 P-E (220 ) 36 3.3 Sample aT (200 °C) aT (220 °C) E-P (180 ) 5.7 8.4 PP 0.65 0.44 E-P (200 ) 11 10 P-E 0.50 0.07 E-P (220 ) 25 11 E-P 0.60 0.27

Table 3: Cross-over frequency wc and elastic limit Table 4: Shift factor a T for the different samples ge values for the samples at different temperatures. (T REF = 180 °C).

© Appl. Rheol. 26 (2016) 33503 | DOI: 10.3933/ApplRheol-26-33503 | 5 | ACKNOWLEDGEMENTS ylene-vinyl acetate copolymer blends, J. Appl. Polym. Sci. 49 (1993) 901 – 912. [13] Kuriakose B, De SK: Studies on the melt flow behavior of The authors acknowledge the financial support of the Nat - thermoplastic elastomers from polypropylene-natural ural Sciences and Research Council of Canada (NSERC). Al - rubber blends, Polym. Eng. Sci. 25 (1985) 630 – 634. so, the technical support of Mr. Yann Giroux for the exper - [14] Prut E, Medintseva T, Dreval V: Mechanical and rheolog - iment is appreciated. Finally, many thanks go to the group ical behavior of unvulcanized and dynamically vulcan - of Manfred Wilhelm at the Karlsruhe Institute of Technol - ized i-PP/EPDM blends, Macromol. Symp. 233 (2006) ogy (KIT) for a student exchange sponsored by FRQNT 78 – 85. [15] Grigoryeva OP, Fainleib AM, Tolstov AL, Starostenko OM, (Fonds de recherche du Québec – Nature et Technologies). Lievana E, Karger-Kocsis J: Thermoplastic elastomers based on recycled high-density polyethylene, ethylene– propylene–diene monomer rubber, and ground tire rub - REFERENCES ber, J. Appl. Polym. Sci. 95 (2005) 659 – 671. [16] Karger-Kocsis J, Mészáros L, Bárány T: Ground tyre rub - [1] Katbab AA, Nazockdast H, Bazgir S: Carbon black-rein - ber (GTR) in thermoplastics, thermosets, and rubbers, J. forced dynamically cured EPDM/PP thermoplastic elas - Mater. Sci. 48 (2013) 1 – 38. tomers. I. Morphology, rheology, and dynamic mechan - [17] Lee SH, Balasubramanian M, Kim JK: Dynamic reaction ical properties, J. Appl. Polym. Sci. 75 (2000) 1127 – 1137. inside co-rotating twin screw extruder. II. Waste ground [2] George J, Ramamurthy K, Varughese KT, Thomas S: Melt rubber tire powder/polypropylene blends, J. Appl. Polym. rheology and morphology of thermoplastic elastomers Sci. 106 (2007) 3209 – 3219. from polyethylene/nitrile-rubber blends: The effect of [18] Mahallati P, Rodrigue D: Effect of feeding strategy on the blend ratio, reactive compatibilization, and dynamic vul - mechanical properties of PP/recycled EPDM/PP-G-MA canization, J. Polym. Sci. B Polym. Phys. 38 (2000) blends, Int. Polym. Proc. 29 (2014) 280 – 286. 1104 – 1122. [19] Mahallati P, Rodrigue D: Effect of feeding strategy on the [3] Prut EV, Erina NA, Karger-Kocsis J, Medintseva TI: Effects properties of PP/recycled EPDM blends, Int. Polym. Proc. of blend composition and dynamic vulcanization on the 30 (2015) 276 – 283. morphology and dynamic viscoelastic properties of [20] Naskar AK, De SK, Bhowmick AK: Thermoplastic elasto - PP/EPDM blends, J. Appl. Polym. Sci. 109 (2008) 1212 – 1220. meric composition based on maleic anhydride-grafted [4] Tchomakov KP, Favis BD, Huneault MA, Champagne MF, ground rubber tire, J. Appl. Polym. Sci. 84 (2002) 370 – 378. Tofan F: Mechanical properties and morphology of [21] Nevatia P, Banerjee TS, Dutta B, Jha A, Naskar AK, Bhow - ternary PP/EPDM/PE blends, Can. J. Chem. Eng. 83 (2005) mick AK: Thermoplastic elastomers from reclaimed rub - 300 – 309. ber and waste plastics, J. Appl. Polym. Sci. 83 (2002) [5] Da Silva ALN, Tavares MIB, Politano DP, Coutinho FMB, 2035 – 2042. Rocha MCG: Polymer blends based on polyolefin elas - [22] Shanmugharaj AM, Kim JK, Ryu SH: UV Surface modifi - tomer and polypropylene, J. Appl. Polym. Sci. 66 (1997) cation of waste tire powder: characterization and its in - 2005 – 2014. fluence on the properties of polypropylene/waste pow - [6] Duvdevani I, Agarwal PK, Lundberg RD: Blends of EPDM der composite, Polym. Test. 24 (2005) 739 – 745. and sulfonated ethylene-propylene-diene (EPDM) rub - [23] Xin ZX, Zhang ZX, Pal K, Lu BX, Deng X, Lee SH, Kim JK: ber with polypropylene: Structure, physical, and rheo - Effects of formulation and processing parameters on the logical properties, Polym. Eng. Sci. 22 (1982) 499 – 506. morphology of extruded polypropylene-(waste ground [7] Gong L, Yin B, Li LP, Yang MB: Morphology and properties rubber tire powder) foams, J. Vinyl. Addit. Technol. 15 of PP/EPDM binary blends and PP/EPDM/nano-CaCO 3 (2009) 266 – 274. ternary blends, J. Appl. Polym. Sci. 123 (2012) 510 – 519. [24] Kim JK, Lee SH, Hwang SH: Experimental investigation [8] Inoue T: Selective crosslinking in polymer blends. II. Its of the morphology development and mechanical prop - effect on impact strength and other mechanical proper - erties of waste ethylene propylene diene monomer/ ties of polypropylene/unsaturated elastomer blends, J. po ly propylene blend in modular intermeshing corotat - Appl. Polym. Sci. 54 (1994) 723 – 733. ing twin-screw extruder, J. Appl. Polym. Sci. 85 (2002) [9] Inoue T, Suzuki T: Selective crosslinking reaction in poly - 2276 – 2282. mer blends. IV. The effects on the impact behavior of [25] Ilyin S, Kulichikhin V, Malkin A: Characterization of ma - PP/EPDM blends (2), J. Appl. Polym. Sci. 59 (1996) terial viscoelasticity at large deformations, Appl. Rheol. 1443 – 1450. 24 (2014) 13653. [10] Ma CG, Zhang MQ, Rong MZ: Morphology prediction of [26] Bueno M, Garcia A, Partl M: Applications of strain-rate ternary polypropylene composites containing elasto- frequency superposition for bituminous binders, Appl. mer and calcium carbonate nanoparticles filler, J. Appl. Rheol. 25 (2015) 65980. Polym. Sci. 103 (2007) 1578 – 1584. [27] Fernandez M, Huegun A, Munoz ME, Anton S: Nonlinear [11] Jain AK, Gupta NK, Nagpal AK: Effect of dynamic cross- oscillatory shear flow as a tool to characterize irradiated linking on melt rheological properties of polypropyle - polypropylene/MWCNT nanocomposites, Appl. Rheol. ne/ethylene-propylene-diene rubber blends, J. Appl. 25 (2015) 45154. Polym. Sci. 77 (2000) 1488 – 1505. [28] Mahi Hassanabadi H, Wilhelm M, Rodrigue D: A rheolog - [12] Koshy AT, Kuriakose B, Thomas S, Premalatha CK, Vargh - ical criterion to determine the percolation threshold in po - ese S: Melt rheology and elasticity of natural rubber-eth - ly mer nano-composites, Rheol. Acta. 53 (2014) 869 – 882.

© Appl. Rheol. 26 (2016) 33503 | DOI: 10.3933/ApplRheol-26-33503 | 6 | [29] Wilhelm M: Fourier-transform rheology, Macromol. amplitude oscillatory shear (LAOS), Prog. Polym. Sci. 36 Mater. Eng. 287 (2002) 83 – 105. (2011) 1697 – 1753. [30] Morrison FA: Understanding rheology, Oxford Universi - [35] Mahi Hassanabadi H, Abbasi M, Wilhelm M, Rodrigue D: ty Press, Oxford (2001). Validity of the modified molecular stress function theory [31] Filipe S, Maia JM, Duarte A, Leal CR, Cidade MT: Influence to predict the rheological properties of polymer of type of compatibilizer on the rheological, and me- nanocomposites, J. Rheol. 57 (2013) 881 – 899. chanical behavior of LCP/TP blends under, different sta - [36] Rheinheimer K, Grosso M, Wilhelm M: Fourier-transform tionary and nonstationary shear conditions, J. Appl. rheology as a universal non-linear mechanical charac - Polym. Sci. 98 (2005) 694 – 703. terization of droplet size and interfacial tension of dilute [32] Lazkano JM, Peña JJ, Muñoz ME, Santamaría A: Role of monodisperse emulsions, J. Coll. Interf. Sci. 360 (2011) drop let deformation on the transient rheological re - 818 – 825. sponse of a polypropylene/liquid-crystal-polymer blend, [37] Salehiyan R, Song HY, Hyun K: Nonlinear behavior of J. Rheol. 46 (2002) 959 – 976. PP/PS blends with and without clay under large ampli - [33] Macaubas PHP, Demarquette NR, Dealy JM: Nonlinear vis - tude oscillatory shear (LAOS) flow, Korea-Australia Rhe - coelasticity of PP/PS/SEBS blends, Rheol. Acta. 44(2005) ol. J. 27 (2015) 95 – 103. 295 – 312. [38] Maani A, Blais B, Heuzey MC, Carreau P: Rheological and [34] Hyun K, Wilhelm M, Klein CO, Cho KS, Nam JG, Ahn KH, morphological properties of reactively compatibilized Lee SJ, Ewoldt RH, McKinley GH: A review of nonlinear thermoplastic olefin (TPO) blends, J. Rheol. 56 (2012) oscillatory shear tests: Analysis and application of large 625 – 647.