Rheological properties and crystalline structure of the dynamically cured EPDM and PP/HDPE ternary blends

The rheological properties and crystalline structure of the polyolefin ternary blends of EPDM/polypropylene/high density polyethylene were studied. Blends were prepared in a laboratory internal mixer by two different methods. In blend–cure process, blending and curing were performed simultaneously and EPDM was cured by dicumyl peroxide (DCP) in the presence of PP/HDPE under shear. The cure–blend was to cure EPDM alone first under shear (dynamic curing) and then mix the cured EPDM with PP and HDPE. The effect of DCP concentration, intensity of the shear mixing, and the rubber/plastic composition were studied using capillary rheometer and X-ray diffractometer. The PP-rich ternary blends showed the effect of the mechanooxidative degradation of PP by shear and peroxide. The melt viscosity increased with increasing DCP concentration in blends of EPDM-rich compositions. X-ray diffraction studies revealed that the inclusion of 25 wt % of linear EPDM in the PP/HDPE mixture for the PP-rich ternary blends changed the crystal structure of polypropylene component in the ternary blends. However, the dynamic curing did not alter the crystal structure of PP or HDPE in the blends.     

Structure and properties of dynamically cured EPDM/PP blends

The structure and properties of polyolefin blends of ethylene–propylene–diene terpolymer (EPDM) and polypropylene were studied. Blends were prepared in a laboratory internal mixer where EPDM was cured with PP under shear with dicumyl peroxide (DCP) at different shear conditions (blend–cure). Blends were also prepared for comparison from EPDM which were dynamically cured in the absence of PP and blended later (cure–blend). The effect of DCP concentration, intensity of the shear mixing, and rubber/plastic composition were studied. In blend–cure, the melt viscosity increased with increasing DCP concentration in blends of 75% EPDM and 25% PP, but it decreased with increasing DCP concentration in blends of 75% PP and 25% EPDM. In cure–blend, however, the melt viscosity increased with increasing DCP concentration for all compositions. The melt viscosity decreased with increasing intensity of the shear mixing presumably due to the formation of the smaller segregated microdomain of the crosslinked EPDM gels in both blend–cure and cure–blend materials. The crystallization rate was higher in EPDM/PP blends than in PP homopolymer. The crystallization rates for various blending conditions were also compared.     

Morphology prediction and the effect of core‐shell structure on the rheological behavior of PP/EPDM/HDPE ternary blends

In this work, the morphologies of polypropylene (PP)/ethylene‐propylene‐diene (EPDM) rubber/high density polyethylene (HDPE) 70/20/10 blends were studied and compared with the predictions of the spreading coefficient and minimum free energy models. The interfacial tension of PP/HDPE, PP/EPDM, and HDPE/EPDM blends were obtained by fitting the experimental dynamic storage modulus data to Palierne's theory. The prediction results showed core‐shell morphology (core of HDPE and shell of EPDM) in PP matrix. The PP/EPDM/HDPE blends were respectively prepared by direct extrusion and lateral injection method. Core‐shell morphology (core of HDPE and shell of EPDM) could be obtained with direct extrusion corresponding to the predicted morphology. The morphology of PP/EPDM/HDPE blends could be effectively controlled by lateral injection method. For PP/EPDM/HDPE blend prepared by lateral injection method, HDPE and EPDM phase were dispersed independently in PP matrix. It was found that the different morphology of PP/EPDM/HDPE blends prepared by two methods showed different rheological behavior. When the core‐shell morphology (core of HDPE and shell of EPDM) appeared, the EPDM shell could confine the deformation of HDPE core significantly, so the interfacial energy contribution of dispersed phase on the storage modulus of blends would be weaken in the low frequency region. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

动态硫化PP／HDPE／EPDM三元共混物的流变性能

本文采用不同的硫化剂，不同的硫化时间，对动态硫化的ＰＰ／ＨＤＰＥ／ＥＰＤＭ三元共混物的流变性能进行了研究。结果表明：１共混体系为假塑体，表现出切力变稀现象；２在低剪切应力下，以Ｍ为硫化剂的粘度与纯机械共混体系的粘度有很大差值，此差值随剪切应力的提高迅速减少；３以ＤＣＰ为硫化剂，体系的粘度低于纯机械共混体系的粘度。     

Silica‐reinforced dynamically vulcanized ethylene–propylene–diene monomer/polypropylene thermoplastic elastomers: Morphology,rheology, and dynamic mechanical properties

Attempts were made to prepare dynamically crosslinked ethylene–propylene–diene monomer/polypropylene (EPDM/PP, 60/40 w/w) blends loaded with various amounts of silica as a particulate reinforcing agent. The dispersion of silica between the two phases under mixing conditions, and also extent of interaction, as the two main factors that influence the blend morphology were studied by scanning electron microscopy. Increasing the silica concentration led to the formation of large‐size EPDM aggregates shelled by a layer of PP. Dynamic mechanical thermal analysis performed on the dynamically cured silica‐loaded blend samples showed reduction in damping behavior with increasing silica content. Higher rubbery‐like characteristics under tensile load were exhibited by the silica‐filled EPDM/PP‐cured blends. However, increasing the silica level to 50 phr led to the enhancement of interface, evidenced by increases in the tensile modulus and extensibility of the blend compared with those of the unloaded sample. Addition of a silane coupling agent (Si69) into the mix improved the mechanical properties of the blend, attributed to the strengthening of interfacial adhesion between the PP matrix and silica‐filled EPDM phase. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2000–2007, 2004     

基体性质对聚丙烯力学性能的影响

采用过氧化二异丙苯(DCP)作为降解剂,以聚丙烯(PP)为基体,以三元乙丙橡胶(EPDM)为增韧剂,研究了EPDM对降解PP/EPDM共混物力学性能的影响,并利用扫描电子显微镜(SEM)对共混体系微观形貌进行了表征。熔体质量流动速率结果表明:随着EPDM质量分数从10%增加到30%时,对应共混物的熔体质量流动速率明显下降,从14.8 g/10 min下降到10.8 g/10 min。随着EPDM用量的增加,共混物的冲击强度明显增大,从30.06J/m增长到90.26 J/m,拉伸强度有所减小。SEM照片显示,随着EPDM用量的增加,共混物中分散相的尺寸明显增大。因为EPDM含量的增加,导致分散的橡胶粒子产生"聚并",从而分散相的相区尺寸增大。     

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     

Influence of coalescence and interfacial tension on the morphology of PP/HDPE compatibilized blends

In this paper, the compatibilization of polypropylene (PP)/high-density polyethylene (HDPE) blend was studied through morphological and interfacial tension analysis. Three types of compatibilizers were tested: ethylene-propylene-diene copolymer (EPDM), ethylene-vinylacetate copolymer (EVA) and styrene-ethylene/butylene-styrene triblock copolymer (SEBS). The morphology of the blends was studied by scanning electron microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the compatibilizer concentration added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA or SEBS. The relative role of interfacial tension reduction and coalescence reduction to particle size reduction was also addressed. It was observed that the role of coalescence reduction is small, mainly for PP/HDPE (90/10) blends compatibilized by EPDM, EVA or SEBS. The results indicated that the role of coalescence reduction to particle size reduction is lower for blends for which interfacial tension between its components is low at compatibilizer saturation.     

PP／HDPE／EPDM三元共混材料的微观形态结构及增韧机理分析

本文用ＳＥＭ对ＰＰ／ＨＤＰＥ／ＥＰＤＭ三元共混材料的微观形态进行了考察,结果发现,ＥＰＤＭ和ＨＤＰＥ在ＰＰ基体中形成了特定的壳核结构,这一微观结构是共混物强度和韧性兼优的内在原因。在对三元洪混材料的银纹,剪切带考察的基础上,将ＨＤＰＥ和ＥＰＤ协同增韧ＰＰ的增韧机理作了阐述。     

Morphology and mechanical properties of biaxially oriented films of polypropylene and HDPE blends

Biaxially oriented films of blends of high-density polyethylene (HDPE) with polypropylene (PP) homopolymer and PP copolymers prepared by twin-screw extrusion and lab-stretcher have been investigated by scanning electron microscopy (SEM), polarized microscopy, differential-scanning calorimeter, and universal testing machine. Three different kinds of PP copolymers were used: (i) ethylene–propylene (EP) random copolymer; (ii) ethylene–propylene (EP) block copolymer; (iii) ethylene–propylene–buttylene (EPB) terpolymer. In the SEM study of the morphology of films of HDPE with various PP blends, phase separation is observed between the PP phase and the HDPE phase for all blends and compositions. In all blends, HDPE serves to reduce the average spherulites size, probably acting as a nucleating agent for PP. The reduction of spherulite size appeared most significantly in the blend of EPB terpolymer and HDPE. A large increase of crystallization temperature was found in the blend of EPB terpolymer and HDPE compared with the unblended EPB terpolymer. For the blend of EPB terpolymer and HDPE, the improvement of tensile strength and modulus is observed with an increase of HDPE content, and this can be considered as a result of the role of HDPE in reducing average spherulite size. © 1994 John Wiley & Sons, Inc.     

Effects of blend composition and dynamic vulcanization on the morphology and dynamic viscoelastic properties of PP/EPDM blends

The morphology and dynamic viscoelastic properties of isotactic polypropylene (PP) blended with oil-free/oil-extended ethylene–propylene–diene (EPDM) rubbers were studied. Unvulcanized and dynamically vulcanized blends with the compositions PP/EPDM = 50/50 and = 30/70 were investigated. The morphology was observed by phase contrasted atomic force microscopy. The dynamic viscoelastic properties were determined with a rheometer of plate–plate configuration. It was shown that the rheological behavior was strongly affected by both the composition and the morphology of the blends. Significant improvement in the flowability of the dynamically vulcanized blends was observed when oil-extended EPDM was used instead of the oil-free version. It was demonstrated that the rheological properties are mostly controlled by the elastomer phase at low frequencies, while in the high-frequency range the influence of PP becomes dominant. The peculiarities in the rheological behavior of the thermoplastic elastomers (uncured blends, TPE) and thermoplastic dynamic vulcanizates (TPV, dynamically cured blends) containing oil-extended EPDMs were traced to a limited compatibility between the PP and EPDM components in the melt. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚烯烃改性PET的研究

通过PET与PP、HDPE、EPDM挤出共混，注射模塑制得试样。经DTA、SEM和力学性能测试，表征了共混体系的热行为、结构形态和力学性能。结果表明，在PET/PP(EPDM、HDPE)共混体系中，加入少量的PP-g-MI(EPDM-g-MAH、PE-g-MI)，可较好地改善PEt与PP(EPDM、HDPE)之间的相容性，使分散相在PET基体连续相中分散均匀，分散相尺寸减小，增加了两相间界面的粘结力；同时对PET的结晶有较强的促进作用，使其冷结晶温度降低，改善了PET的加工性能；并且能大幅度提高共混物的冲击强度。     

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.     

Recycling of commingled plastics waste containing polypropylene,polyethylene, and paper

Polymer waste recycling is a major technical problem, because large amounts of synthetic polymers are produced every day and polymeric wastes are gathered from municipal solid wastes. There are a few polyolefins, such as polyethylene (PE) and polypropylene (PP) with huge amounts of paper in the waste materials. In order to recycle the commingled plastics waste that contains paper, hydrolytic treatment is needed prior to conventional processing. In this project, the optimum conditions of hydrolytic treatment of paper and the mechanical properties and morphological state of different compositions of PP high‐density PE (HDPE) blends with paper were studied. Ethylene‐propylene‐diene copolymer (EPDM) was added to improve the mechanical properties of blends. The results show that the hydrolytic treatment of paper improves the mechanical properties, such as the tensile strength and modulus of the PP/HDPE/paper composites relative to the untreated samples, and up to 30% paper can be added to commingled PP and HDPE blends. The EPDM was used as an impact modifier. The plastics waste containing paper can be used in applications such as artificial wood. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2573–2577, 2001     

The Effects of Dynamic Vulcanization by Dicumyl Peroxide (DCP) and N,N-m-Phenylene Bismaleimide (HVA-2) on the Properties of Polypropylene (PP)/Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Blends

ABSTRACT

This paper discusses some properties of the polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends, such as tensile properties, heat resistance, gel content, and morphology. Dicumyl peroxide (DCP) and N,N-m-phenylene bismaleimide (HVA-2) and their combination were applied in PP/EPDM/NR blends as cross-link agents. In terms of tensile properties, the combination of DCP with HVA-2 shows the highest tensile strength and elongation at break in all PP/EPDM/NR blend ratios compared to similar blends, except with DCP or HVA-2 alone. The addition of HVA-2 produced blends with good heat resistance, while the combination of DCP with HVA-2 shows the highest gel content dealing with the cross-links formation. SEM micrographs from the surfaces extraction of the blends support that the cross-links have occurred during dynamic vulcanization process.     

Application of phase dispersion–crosslinking synergism on recycling commingled plastic wastes

A tetra‐component blend, consisting of low‐density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), was studied as a model system of commingled plastic wastes (LDPE/PVC/PP/PS, mass ratio: 70/10/10/10). Effects of chlorinated polyethylene (CPE), ethylene–propylene–diene monomer (EPDM), styrene–butadiene–styrene (SBS), and their mixture (CPE/EPDM/SBS, mass ratio: 2/2/2) on the mechanical properties and morphology of the system were investigated. With addition of several elastomers and their mixture, the tensile strength of the blends decreased slightly, although both the elongation at break and the impact strength increased. Among these elastomers, EPDM exhibited the most significant impact modification effect for the tetra‐component blends. SBS and the mixture have a good phase‐dispersion effect for the tetra‐component blend. By adding a crosslinking agent [dicumyl peroxide (DCP)], the mechanical properties of the tetra‐component blends also increased. When either SBS or the mixture was added to the blend together with DCP, the probability that the crosslinking agent (DCP) would be at the interface improved because of the phase‐dispersion effect of SBS. Therefore, more co‐crosslinked products will form between LDPE and other components. Accordingly, remarkable improvement of the interfacial adhesion and hence the mechanical properties of the tetra‐component blends occurred. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2947–2952, 2001     

Synchronous toughening and reinforcing of polypropylene with ultrahigh‐molecular‐weight polyethylene via melt blending: Mechanical properties,morphology, and rheology

Blending systems based on polypropylene (PP) and ultrahigh‐molecular‐weight polyethylene (UHMWPE) were prepared via a melt extrusion by the four‐screw and the twin‐screw extruders, respectively. The mechanical evaluation demonstrated that the synchronous toughening and reinforcing effects could be achieved from the combination of the PP and the UHMWPE, in which the toughness and the tensile properties could be improved with increasing the UHMWPE content, and achieved optimal values at a weight ratio of PP/UHMWPE (85/15). EPDM can be used as a compatibilizer to improve the compatibility and the interfacial adhesion between the PP and the UHMWPE. This resulted in more effective toughening and reinforcing effects. In contrast, for the PP/UHMWPE blends prepared by the normal twin‐screw extruder, the poor dispersion capacity for the UHMWPE resulted in a deterioration of all mechanical parameters. Morphological observation revealed that the UHMWPE domain was well distributed as tiny particles in the PP matrix, which was confirmed by the differential scanning calorimetry analysis. The toughening effect was attributed to the energy dissipation caused by these rigid tiny particles that detached from the matrix to initiate the local matrix shear yield and formed the void. Rheological investigation demonstrated that there was an interesting composition dependence of viscosity, for which the melt viscosities of the PP/UHMWPE blends decreased when 5 wt % UHMWPE was added, and then began to increase as the UHMWPE content continued to increase. However, this dependence on composition became weaker because of the compatibilization of the EPDM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3498–3509, 2006     

DCP用量对动态硫化POE/PP热塑性弹性体性能的影响

研究了过氧化二异丙苯(DCP)用量对动态硫化乙烯一辛烯共聚物聚丙烯(POE/PP)体系的物理性能以及PP结晶形态和POE相态结构的影响。结果表明:随DCP用量的增加,POE/PP体系的交联密度增大,而断裂伸长率、永久变形和拉伸强度下降。过量DCP的加人会导致PP降解,使体系的熔体流动速率随DCP用量的增加呈上升趋势。DSC分析表明,随着DCP用量的增加,POE/PP体系结晶度下降。微观分析得出,DCP对POE/PP体系相态结构影响显著,当DCP用量为1份时交联POE以较小的颗粒均匀分布于PP连续相中。     

Mechanical properties,morphological structure,and thermal behavior of dynamically photocrosslinked PP/EPDM blends

A dynamically photocrosslinked polypropylene (PP)/ethylene–propylene–diene (EPDM) rubber thermoplastic elastomer was prepared by simultaneously exposing the elastomer to UV light while melt‐mixing in the presence of a photoinitiator as well as a crosslinking agent. The effects of dynamic photocrosslinking and blend composition on the mechanical properties, morphological structure, and thermal behavior of PP/EPDM blends were investigated. The results showed that after photocrosslinking, tensile strength, modulus of elasticity, and elongation at break were improved greatly. Moreover, the notched Izod impact strength was obviously enhanced compared with corresponding uncrosslinked blend. Scanning electron microscopy (SEM) morphological analysis showed that for uncrosslinked PP/EPDM blends, the cavitation of EPDM particles was the main toughening mechanism; whereas for dynamically photocrosslinked blends, shear yielding of matrix became the main energy absorption mechanism. The DSC curves showed that for each dynamically photocrosslinked PP/EPDM blend, there was a new smaller melting peak at about 152°C together with a main melting peak at about 166°C. Dynamic mechanical thermal analysis (DMTA) indicated that the compatibility between EPDM and PP was improved by dynamic photocrosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3371–3380, 2004     

Synergetic toughness and morphology of poly(propylene)/nylon 11/maleated ethylene‐propylene diene copolymer blends

Polypropylene (PP)/nylon 11/maleated ethylene‐propylene‐diene rubber (EPDM‐g‐MAH) ternary polymer blends were prepared via melt blending in a corotating twin‐screw extruder. The effect of nylon 11 and EPDM‐g‐MAH on the phase morphology and mechanical properties was investigated. Scanning electron microscopy observation revealed that there was apparent phase separation for PP/EPDM‐g‐MAH binary blends at the level of 10 wt % maleated elastomer. For the PP/nylon 11/EPDM‐g‐MAH ternary blends, the dispersed phase morphology of the maleated elastomer was hardly affected by the addition of nylon 11, whereas the reduced dispersed phase domains of nylon 11 were observed with the increasing maleated elastomer loading. Furthermore, a core‐shell structure, in which nylon 11 as a rigid core was surrounded by a soft EPDM‐g‐MAH shell, was formed in the case of 10 wt % nylon 11 and higher EPDM‐g‐MAH concentration. In general, the results of mechanical property measurement showed that the ternary blends exhibited inferior tensile strength in comparison with the PP matrix, but superior toughness. Especially low‐temperature impact strength was obtained. The toughening mechanism was discussed with reference to the phase morphology. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008