Properties of dynamically vulcanized ethylene–propylene–diene copolymer/polypropylene blends

In this study, vulcanized thermoplastic elastomers were produced through the formation of crosslinks with peroxide for different ratios of ethylene–propylene–diene copolymer to polypropylene. Mixing was performed with a twin‐screw extruder. Afterward, the yield, tensile strength, elastic modulus, elongation, Izod impact strength, hardness, melt flow index, Vicat softening point, heat deflection temperature, and density of the crosslinks were determined. The thermal transition temperatures and microstructure were determined with differential scanning calorimetry and scanning electron microscopy, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3895–3902, 2007     

Carbon black‐reinforced dynamically cured EPDM/PP thermoplastic elastomers. I. Morphology,rheology, and dynamic mechanical properties

The structure development, rheological behavior, and viscoelastic properties of carbon black‐filled dynamically vulcanized thermoplastic elastomers based on the ethylene–propylene–diene terpolymer (EPDM) and polypropylene (PP) with the ratio range of 50/50 to 80/20 were studied and compared with similar but unfilled samples. Two‐phase morphology was observed at all ratios for the dynamically cured samples in which rubber particles are dispersed in the thermoplastic matrix. Carbon black distribution in each phase and damping behavior was found to be dependent upon the mixing condition and route of carbon black feeding. However, carbon black tends to stay mainly in the rubber phase, which leads to increase in the viscosity difference and, therefore, increase in the rubber particle size. Tensile strength and rupture energy increased with carbon black loading. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1127–1137, 2000     

Preparation and properties of peroxide dynamically vulcanized polypropylene/ethylene‐propylene‐diene monomer/zinc dimethacrylate thermoplastic olefin

Attempts were made to prepare the polypropylene (PP) /ethylene‐propylene‐diene monomer (EPDM) blends with zinc dimethacrylate (ZDMA) via peroxide dynamic vulcanization. PP was melt‐mixed with EPDM and ZDMA at different compositions (PP/EPDM/ZDMA, i.e., 70/30/0, 70/30/3, 70/30/6, and 70/30/9, w/w/w) using an internal mixer at 50 rpm rotor speed. The addition of ZDMA improved the rheological properties of the resulting materials in the melt state. The morphological studies revealed that the addition of ZDMA led to an improvement of size reduction and distribution uniformity for crosslinked EPDM phase. ZDMA showed a positive effect on the mechanical properties of the PP/EPDM/ZDMA composites, particularly on the toughness and extensibility. With the incorporation of ZDMA, the izod impact strength and the elongation of PP/EPDM/ZDMA composites increased from 41 kJ/m² to 72 kJ/m² and 110% to 495%, respectively. The crystallization behaviors analysis indicated that the addition of ZDMA promoted the nucleation process of PP but the crystallinity of the PP phase was decreased at the meantime. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Thermoplastic elastomers based on high‐density polyethylene,ethylene–propylene–diene terpolymer,and ground tire rubber dynamically vulcanized with dicumyl peroxide

Thermoplastic vulcanizates (TPVs) based on high‐density polyethylene (HDPE), ethylene–propylene–diene terpolymer (EPDM), and ground tire rubber (GTR) were dynamically vulcanized with dicumyl peroxide (DCP). The polymer blend was composed of 40% HDPE, 30% EPDM, and 30% GTR, and the concentration of DCP was varied from 0.3 to 3.6 parts per hundred rubber (phr). The properties of the TPVs were determined by evaluation of the gel fraction content and the mechanical properties. In addition, IR spectroscopy and differential scanning calorimetry analysis were performed as a function of the DCP content. Decreases in the Young's modulus of the blends and the crystallinity of HDPE were observed when the content of DCP was greater than 1.8 phr. The results regarding the gel content indicate that the presence of DCP promoted the crosslinking of the thermoplastic matrix, and optimal properties were obtained with 1.5% DCP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39901.     

三元乙丙橡胶/聚丙烯动态硫化热塑性弹性体的相态结构

用扫描电镜研究了三元乙丙橡胶(EPDM)聚/丙烯(PP)动态硫化热塑性弹性体(TPV)相态结构的形成过程,探讨了交联密度、制备工艺、螺杆转速对EPDM/PP TPV相态结构的影响。结果表明,采用以酚醛树脂为硫化剂的动态硫化工艺制备的EPDM/PP TPV,其相态结构实现了由EPDM和PP组成的双连续相到以EPDM为分散相、PP为连续相的转变;当硫化剂用量为7份时,橡胶相硫化速率和交联密度最大;当螺杆转速为180 r/m in时,反应性挤出工艺较之密炼机工艺制备的EPDM/PP TPV的橡胶粒子更细小、分散更均匀。     

Structure and properties of peroxide dynamically vulcanized polypropylene/ethylene–propylene–diene/zinc dimethacrylate composites

Peroxide dynamically vulcanized thermoplastic olefin (TPO) based on polypropylene (PP)/ethylene–propylene–diene (EPDM) loaded with zinc dimethacrylate (ZDMA) was prepared. The addition of ZDMA improved the complex viscosity of the resulting materials in the melt state significantly, as determined from oscillatory rheology analyses. Dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM) examinations were performed to evaluate the structure of the PP/EPDM/ZDMA composite. Atomic force microscope (AFM) and scanning electron microscopy (SEM) were used to study the morphology. The degree of crystallinity was evaluated using X‐ray diffraction method (XRD). The results revealed that incorporation of ZDMA resulted in a size reduction of the rubber droplets and improved the compatibility between rubber and PP phases. The nanoparticles of the polymerized ZDMA (PZDMA) served as an effective nucleating agent for the crystallization of PP. The rheological properties and mechanical properties were improved by ZDMA. Particularly, the izod impact strength of the PP/EPDM/ZDMA (80/20/6, w/w) composite is nearly 2 times higher than the PP/EPDM (80/20, w/w) and 12 times higher than the PP; besides, the elongation at break of the PP/EPDM/ZDMA (80/20/6, w/w) is 3 times higher than that of the PP/EPDM (80/20, w/w) and 6 times higher than the PP. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Mechanical and morphological properties of white rice husk ash filled polypropylene/ethylene‐propylene‐diene terpolymer thermoplastic elastomer composites

The performance of white rice husk ash (WRHA) as filler for polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) thermoplastic elastomer (TPE) composites was investigated. The composites with different filler loadings were prepared in a Brabender plasticorder internal mixer. Both unvulcanized and dynamically vulcanized composites were prepared. Mixing and vulcanization processes of the composites were monitored through the typical Brabender torque‐time curves. The mechanical properties and morphology of the composites were also studied. The Brabender torque curves revealed that the dynamic vulcanization process employed was successful and incorporation of filler has no adverse effect on the processibility of the composites. Incorporation of WRHA improves the tensile modulus and flexural modulus and lowers tensile strength, elongation at break, tear strength, and toughness of both types of composites. Dynamic vulcanization significantly enhances the mechanical and TPE properties of the composites. Dynamic mechanical analysis (DMA) study revealed the existence of two phases in both types of composites. It further shows that neither dynamic vulcanization nor filler agglomeration has played a prominent role in the compatibility of the composites. Thermogravimetric investigation shows that dynamic vulcanization or WRHA loading has not adversely affected the thermal stability of the composites. The scanning electron micrographs provide evidence for the tendency to form filler agglomerates with increasing filler loading, better filler dispersion of dynamically vulcanized composites over unvulcanized composites, and effective vulcanization of elastomer phase of the composites in the presence of filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 438–453, 2002     

Structure and mechanical properties of nanodispersed fibrous silicate‐reinforced ethylene–propylene–diene monomer nanocomposites

In this study, ethylene–propylene–diene monomer (EPDM)/fibrillar silicate (FS) nanocomposites were successfully prepared by mechanically blending EPDM with FS, which was modified by silane coupling agent KH570 containing methacryloxy group. The effects of silane content and modified FS on the dispersion of FS and mechanical properties of the composites were investigated. The impact of water in FS on mechanical properties of the composites was also evaluated. The results showed that modified FS could be dissociated into nanofibers dispersing evenly in the EPDM matrix by increasing substantially the loading of silane through the mechanical blending. The optimum loading level of silane coupling agent was up to 24 phr/100 phr FS. Silane KH570 could improve the dispersion of FS and strengthen nanofibers–rubber interfacial adhesion even at the loading of as high as 50 phr FS, making FS to exhibit excellent reinforcement to EPDM. Too much FS could not be completely dissociated into nanofibers, slowing down further improvement. The EPDM/FS composites exhibited the similar stress–strain behavior and obvious mechanical anisotropy with short microfiber‐reinforced rubber composites. With the increase in silane coupling agent and modified FS, the number of nanofibers increased because of the exfoliation of FS microparticles; thus, the mechanical behaviors would become more obvious. It was suggested that the free water in FS should be removed before mechanically blending EPDM with FS because it obviously affected the tensile properties of the composites. Regardless of whether FS was dried or modified, the EPDM/FS composites changed little in tensile strength after soaked in hot water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties of thermoplastic elastomers based on silicone rubber and an ethylene–octene copolymer by dynamic vulcanization

Thermoplastic vulcanizates (TPVs) are a special class of thermoplastic elastomers that are generally produced by the simultaneous mixing and crosslinking of a rubber with a thermoplastic polymer at an elevated temperature. Novel peroxide‐cured TPVs based on blends of silicone rubber and the thermoplastic Engage (an ethylene–octene copolymer) have been developed. These TPVs exhibit very good overall mechanical and electrical properties. With an increasing concentration of dicumyl peroxide, the tensile strength, modulus, and hardness of the TPVs increase, whereas the elongation at break decreases. Significant correlations have been obtained from oscillating disc rheometer torque values with various physical properties, such as the modulus and tension set of the TPVs. The aging characteristics and recyclability of the silicone‐based TPVs are also excellent. Scanning electron microscopy photomicrographs of the TPVs have confirmed a dispersed phase morphology. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermoplastic elastomers based on recycled high‐density polyethylene,ethylene–propylene–diene monomer rubber,and ground tire rubber

High‐performance thermoplastic elastomers (TPEs), based on recycled high‐density polyethylene (HDPE^R), olefinic type ethylene–propylene–diene monomer rubber (EPDM), and ground tire rubber (GTR) treated with bitumen, were prepared by using dynamic vulcanization technology, and their structure–property relationships were investigated. It was established that special pretreatment of GTR by bitumen confers outstanding mechanical properties on the resulting TPEs. TPEs, containing GTR pretreated by bitumen, exhibit thermal behavior similar to that of the HDPE^R/EPDM basic blend in the temperature region up to about 340°C. Rheological measurements showed that bitumen acts as an effective plasticizer for the GTR‐containing TPEs. SEM, DSC, and DMTA results revealed improved adhesion between the particles of GTR treated by bitumen and the surrounding thermoplastic matrix, compared to that of the untreated GTR particles. It was concluded that bitumen acts as an effective devulcanizing agent in the GTR treatment stage. In the following steps of TPE production, bitumen acts simultaneously as a curing agent for the rubber components (EPDM/GTR) and as a compatibilizer for the blend components. GTR‐containing TPEs, prepared by extrusion technology, were reprocessed (by passing through the extruder six times) without any observable changes in their tensile properties, thermal stability, and melt viscosity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 659–671, 2005     

In situ reactive compatibilization and reinforcement of peroxide dynamically vulcanized polypropylene/ethylene‐propylene‐diene monomer tpv by zinc dimethacrylate

This work demonstrates an approach of in situ reactive compatibilization between polypropylene (PP) and ethylene‐propylene‐diene monomer (EPDM) by using ZDMA as a compatibilizer and, simultaneously, as a very strong reinforcing agent. With 7phr ZDMA in the PP/EPDM (30/70, w/w) thermoplastic vulcanizate (TPV), the tensile strength and elongation at break were increased from 5.3 MPa and 222% up to 11.2 MPa and 396%, respectively. Increasing the PP concentration further improved mechanical properties of the TPVs with ZDMA. This tremendous reinforcing as well as the compatibilization effect of the ZDMA was understood by polymerization of ZDMA and ZDMA reacting with EPDM and PP during peroxide induced dynamic vulcanization. A peculiar nano‐composite structure that the crosslinked rubber particles were “bonded” by a transition zone which containing numerous of nano‐particles with dimensions of about 20–30 nm was observed from transmission electron microscopy (TEM). Scanning electron microscopy (SEM) results showed that increase of PP/EPDM ratio reduced the size of crosslinked EPDM particles. Moreover, we found that the ZDMA reinforced EPDM particles resulted in a higher tan δ peak temperature for EPDM phase and built “filler‐filler”‐like networking in the PP melt. POLYM. COMPOS. 34:1357–1366, 2013. © 2013 Society of Plastics Engineers     

Dynamic mechanical analysis of ethylene–propylene–diene monomer rubber and styrene–butadiene rubber blends

The effects of blend ratio, crosslinking systems, and fillers on the viscoelastic response of ethylene–propylene–diene monomer (EPDM)/styrene–butadiene rubber (SBR) blends were studied as functions of frequency, temperature, and cure systems. The storage modulus decreased with increasing SBR content. The loss modulus and loss tangent results showed that the EPDM/SBR blend vulcanizate containing 80 wt % EPDM had the highest compatibility. Among the different cure systems studied, the dicumyl peroxide cured blends exhibited the highest storage modulus. The reinforcing fillers were found to reduce the loss tangent peak height. The blend containing 40 wt % EPDM showed partial miscibility. The dispersed EPDM phase suppressed the glass‐transition temperature of the matrix phase. The dynamic mechanical response of rubbery region was dominated by SBR in the EPDM–SBR blend. The morphology of the blend was studied by means of scanning electron microscopy. The blend containing 80 wt % EPDM had small domains of SBR particles dispersed uniformly throughout the EPDM matrix, which helped to toughen the matrix and prevent crack propagation; this led to enhanced blend compatibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Study of polypropylene/ethylene‐propylene‐diene monomer blends reinforced with sisal fibers

Thermoplastics reinforced with natural fibers have attracted much attention from researchers because of their advantages, especially regarding environmental aspects. However, poor impact strength, particularly at low temperatures, limits the application of some thermoplastics, such as polypropylene (PP). To minimize this drawback, impact modifiers have been used, including the terpolymer of ethylene‐propylene‐diene (EPDM). In this work, PP/EPDM/sisal composites of distinct compositions were investigated focusing on the effect of the alkali (NaOH) treatment of the vegetable fiber on the composites properties regarding physical, mechanical, thermal, and morphological behavior. The results indicated that flow rate decreases at higher fiber content due to flow hindering by the presence of the fibers. The addition of the fiber, in general, increased Young's modulus and strength (tensile and flexural), whereas impact strength increased for higher EPDM content. The alkali treatment was considered generally efficient in terms of mechanical properties, even though this was not found in the dynamic mechanical analysis. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Dynamic mechanical properties of polypropylene‐g‐maleic anhydride and ethylene–propylene–diene terpolymer blends: Effect of blend preparation methods

In this work, we attempted two different ways of processing to improve interfacial adhesion of polypropylene (PP) and ethylene–propylene–diene terpolymer (EPDM) by introducing maleic anhydride (MAH); In one way, the in situ grafting and dynamic vulcanization (ISGV) were performed simultaneously from PP and EPDM with MAH in the presence of dicumyl peroxide (DCP) in an intensive mixer. In another way, PP was first grafted with MAH and then the PP‐g‐MAH was blended with EPDM in the intensive mixer in the presence of DCP by the dynamic vulcanization (DV). It was found that the glass transition temperatures (T_gs) of both PP and EPDM phases were shifted to higher temperature as the EPDM content increased for the blends prepared by both IGSV and DV methods, mainly due to the crosslinking of EPDM. The higher T_gs and larger storage moduli were observed for the blends prepared by the ISGV method than those prepared by the DV method, while the morphology showed that the size reduction of dispersed particles in latter blends was larger than that of the former blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2777–2784, 2000     

Effect of dynamic crosslinking on tensile yield behavior of polypropylene/ethylene‐propylene‐diene rubber blends

Tensile yield behavior of the blends of polypropylene (PP) with ethylene‐propylene‐diene rubber (EPDM) is studied in blend composition range 0–40 wt % EPDM rubber. These blends were prepared in a laboratory internal mixer by simultaneous blending and dynamic vulcanization. Vulcanization was performed with dimethylol phenolic resin. For comparison, unvulcanized PP/EPDM blends were also prepared. In comparison to the unvulcanized blends, dynamically vulcanized blends showed higher yield stress and modulus. The increase of interfacial adhesion caused by production of three‐dimensional network is considered to be the most important factor in the improvement. It permits the interaction of the stress concentrate zone developed at the rubber particles and causes shear yielding of the PP matrix. Systematic changes with varying blend composition were found in stress‐strain behavior in the yield region, viz., in yield stress, yield strain, width of yield peak, and work of yield. Analysis of yield stress data on the basis of the various expressions of first power and two‐thirds power laws of blend compositions dependence and the porosity model led to consistent results from all expression about the variation of stress concentration effect in both unvulcanized and vulcanized blend systems. Shapes and sizes of dispersed rubber phase (EPDM) domains at various blend compositions were studied by scanning electron microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2104–2121, 2000     

SBR/PP动态硫化热塑性弹性体的制备及其力学性能的研究

研究了聚丙烯（PP）牌号、橡塑比、硫化体系和不同填料对丁苯橡胶／聚丙烯（SBR／PP）动态硫化热塑性弹性体力学性能的影响。研究结果表明：选用牌号为EPC-30R—H的PP与SBR共混，橡塑比为70／30（质量比），硫磺的用量为1．25份左右（或DCP的用量为1．5份左右），沉淀白炭黑用量为30份，而滑石粉用量为30份时，共混物的综合力学性能较好。     

Effect of dynamic crosslinking on impact strength and other mechanical properties of polypropylene/ethylene‐propylene‐diene rubber blends

The deformation and fracture behavior of several dynamic vulcanizate blends of isotactic polypropylene with ethylene‐propylene‐diene rubber (EPDM) was examined and compared with those of uncrosslinked blends of PP/EPDM. These blends were prepared by melt mixing in an internal mixer at 190°C in a composition range of 10–40 wt % EPDM rubber. The variation in yield stress, the strength of fibrils of the craze, and the number density of the EPDM rubber domains (morphology fixation) that are dominant factors for enhancing interfacial adhesion and toughness in dynamic vulcanizate blends were evaluated. The ductility and toughness of these materials were explained in light of the composition between crack formation and the degree of plastic deformation through crazing and shear yielding. The physicomechanical properties including the hardness, yield stress, Young's modulus, percentage elongation, impact strength, flexural strength, and flexural modulus of dynamic vulcanized blends were found to be consistent and displayed higher values compared with uncrosslinked blends. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM rubber were also considered to contribute to the improvement in the impact strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2089–2103, 2000     

The synergistic effect of aluminum hypophosphide and nanosilica on flame‐retarded ethylene–propylene–diene monomer rubber

The influence of aluminum hypophosphide (AlHPi) and nanosilica on the flame‐retardant and mechanical property of ethylene–propylene–diene monomer (EPDM) rubber was evaluated by limiting oxygen index, and the value of tensile strength and elongation at break. The results show that the introduction of nanosilica into the EPDM/AlHPi blends can not only further improve the flame‐retardant property but also improve the tensile strength and elongation at break significantly, showing a synergistic effect between AlHPi and nanosilica. The flame‐retardant mechanism was further studied by X‐ray diffraction (XRD), thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), and scanning electron microscope (SEM). The results of XRD and TG–DSC indicate that AlHPi will melt along with oxidation at about 337°C, which is helpful to full contact with nanosilica and to enhance the interaction between them; and will further recrystallize above 540°C, which is benefited to enhance the mechanical strength of char layer. The char morphological study by SEM shows that the char layer for the sample with both AlHPi and nanosilica is strong, more uniform and dense, and the scale of the holes in the char layer is smaller compared with the char layer of samples with AlHPi or nanosilica alone. The TG–DSC results show that the sample with both AlHPi and nanosilica has the weakest weight loss rate and heat release rate, compared with the samples with either of them, which is another evidence of the synergistic flame retardant effect between AlHPi and nanosilica. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal and mechanical properties of silicon rubber/cis‐polybutadiene rubber/ethylene–propylene–diene monomer blends

Considering the properties of silicon rubber, ethylene–propylene–diene monomer (EPDM), and cis‐polybutadiene rubber (BR), a blend made by a new method was proposed in this article; this blend had thermal resistance and good mechanical properties. The morphology of the blend was studied by SEM, and it was found that the adhesion between the phases of BR, EPDM, and polysiloxanes (silicon rubber) could be enhanced, and the compatibility and covulcanization were good. The influence of the mass ratio of peroxide and silica on the mechanical properties and thermal resistance of the blend was studied. The results showed that the mechanical properties and thermal resistance of the blend were improved when silicon rubber/BR/EPDM was 20/30/50, dicumyl peroxide/sulfur was 2.5/2.5, and the amount of silica was 80 phr. The integral properties of rubber blend had more advantages than did the three rubbers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4462–4467, 2006     

动态硫化溴化丁基橡胶/三元共聚尼龙热塑性弹性体力学性能的影响因素

采用动态硫化法制备了溴化丁基橡胶/三元共聚尼龙热塑性弹性体(BIIR/CO-PA TPV),考察了硫化体系、增容剂、橡塑比、硫化温度、返炼次数对BIIR/CO-PA TPV力学性能的影响,并对TPV脆断面的微观形貌进行了观察。结果表明,无论采用过氧化二异丙苯还是ZnO为硫化体系,BIIR混炼胶的硫化效果均较好。添加增容剂可以改善BIIR与CO-PA的相容性,提高TPV的力学性能;马来酸酐接枝乙烯-辛烯共聚物与氯化聚乙烯的增容效果相当。橡塑比(质量比)为7∶3~6∶4、硫化温度为180℃时,制备的TPV力学性能最好。随着返炼次数的增加,TPV的力学性能降低。