Ethylene-propylene Rubber Phase Research Articles

The orientation of the dispersed phase and crystals in an injection-molded impact polypropylene copolymer

The orientation of the dispersed phase and crystals in the injection-molded bar of an impact polypropylene copolymer (IPC) containing isotactic polypropylene (iPP), ethylene-propylene rubber (EPR) and a β-nucleating agent (β-NA) were studied simultaneously. In the IPC, iPP and EPR act as the matrix and dispersed phase, respectively. The EPR is amorphous and the iPP is crystallizable in α- and β-crystalline forms in the presence of the β-NA. The orientation and orientation distribution for both of the EPR phase and the iPP crystals, as well as the crystallization behavior of iPP, were investigated by two-dimensional wide-angle X-ray diffraction (2D-WAXD), two-dimensional small-angle X-ray scattering (2D-SAXS), scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The results of the experiment show that orientation exists for both the EPR phase and the iPP crystals. But their orientation distribution manifests an opposite tendency. The EPR phase was observed to be highly oriented in the core layer but the orientation of the iPP crystals was weakened gradually from skin to core. The difference in the orientation behavior between the EPR phase and the iPP crystals reflects the distinct response of the micrometer-scale EPR particles and nanometer-scale iPP chains upon the flow field and temperature gradient in the mold. The diffraction geometry of the β-crystals has also been discussed in detail. The observations in this study may shed light on the study in the structure and property relationship for the IPC injection-molded products.

Morphological analysis of high-impact polypropylene using X-ray microCT and AFM

Detailed visualization and understanding of high-impact polypropylene (hiPP) particle morphology and its evolution on the scale of entire particles is important for obtaining the required mechanical and optical properties of this material and for the quantitative description of mass transport in hiPP particles. Shape and size of hiPP particles as well as the spatial distribution of pores, PP homopolymer and ethylene-propylene rubber (EPR) phases in individual particles is visualized by micro-computed tomography (microCT) and atomic force microscopy (AFM) techniques. The morphology of each hiPP particle depends on many factors including catalyst system, the initial pore structure of porous catalyst and homopolymer particles, reactor conditions and particle history. These factors affect the required content, the constitution and the spatial distribution of EPR phase. To understand particle morphology and its evolution in a quantitative way we need a high-quality morphology data. The presented results include the AFM visualization of rubber layer on the surface of hiPP particles, the microCT visualization of not only porous homopolymer PP particles but also of large rubber domains in hiPP particles and the AFM mapping of the fine networked structure of EPR rubber and pores in hiPP particles.

Effect of Ethylene‐Propylene Copolymer Composition on Morphology and Surface Properties of Impact Poly(propylene) Copolymer

AbstractSummary: Impact poly(propylene) copolymers (IPC) having various ethylene‐propylene rubber (EPR) compositions were prepared using a high activity Ziegler‐Natta catalyst. EPR composition was characterized by temperature rising elution fractionation (TREF) analysis and FT‐IR spectroscopy. Effect of EPR composition on the morphology and surface properties of IPC was investigated by scanning electron microscopy (SEM), 3D profiler, and gloss meter. Composition and amount of amorphous and crystalline EPR were quantified by TREF and found to be dependent on the ethylene content in EPR. From the SEM result, it was found EPR composition has a strong influence on its shape and size. IPCs containing propylene‐rich EPR exhibited a finer dispersion of EPR phase. The surface roughness decreased with decreasing ethylene content in EPR. The comparison of EPR composition and morphology and surface properties exhibited strong correlations.

Characterization of impact polypropylene copolymers by solvent fractionation

The compositional heterogeneity of two impact polypropylene copolymers (IPCs) was studied by a combinatory investigation of temperature rising elution fractionation (TREF) and solvent fractionation. The chain structures and composition of fractions obtained from solvent fractionation were examined in detail. The TREF results shows that there are much more E-P segmented copolymer and more uniform distribution of ethylene sequence in IPC-1, which is responsible for its better comprehensive mechanical performance. The fractions from hexane and heptane are ethylene-propylene rubber phase and E-P block copolymers respectively. The result of solvent fractionation method also shows that custom hexane or heptane extractions can not extract the E-P copolymer completely.

The effect of electron beam irradiation on dynamic shear rheological behavior of a poly (propylene-co-ethylene) heterophasic copolymer

In this study the effect of electron beam irradiation on rheological properties of a poly (propylene-co-ethylene) heterophasic copolymer is evaluated. Using dynamic viscoelastic measurement in the linear viscoelastic range of deformation, it is observed that the complex viscosity and dynamic modulus of polypropylenes were decreased by increasing the irradiation dose. Polypropylene heterophasic copolymers consist of ethylene propylene rubber phase dispersed in polypropylene homopolymer matrix. The high energy electron beams simultaneously affect both isotactic polypropylene (iPP) matrix and ethylene propylene dispersed phase. The molecular chains of polypropylene homopolymer phase breakdown to smaller species, those are prone to degradation and branching as well. Increase in the melt flow rate behavior and shifting the cross-over point to higher frequencies and increase in melt strength are due to this phenomenon. At the same time, the ethylene propylene phase of the polypropylene copolymer cross-links due to irradiation, and a significant effect on the rheological behavior of samples are observed. The mathematical modeling of complex viscosity behavior revealed the conformity of experimental data with modified Carreau equation. Copyright © 2010 John Wiley & Sons, Ltd.

Rheological, thermal, and morphological properties of blends based on poly(propylene), ethylene propylene rubber, and ethylene‐1‐octene copolymer that could result from end of life vehicles: Effect of maleic anhydride grafted poly(propylene)

AbstractThe objective of this work is to study the properties of blends that could result from the recycling of end‐of‐life vehicles (ELV). While ethylene propylene rubber (EPR) and ethylene propylene diene monomer (EPDM) have been used extensively as elastomeric additives in poly(propylene) (PP), they can be substituted by ethylene‐1‐octene copolymer (EOC). As a consequence, the matter resulting from the sorting of ELV might be more complex and made of PP, EPR, and EOC. The effect of incorporating EOC [that is a polyethylene elastomer (PEE)] and maleic anhydride grafted polypropylene (PP‐g‐MAH) on the rheological, thermal, and morphological properties of PP/EPR blends has been investigated. Blends of various compositions (with and without compatibilizer) were prepared using a corotating twin‐screw extruder. The results were compared to the ones presented by a commercial (PP/EPR) blend. The EPR phase is dispersed in the form of spherical particles in (PP/EPR). The EOC phase is dispersed in the form of aggregated particles. Dynamic viscoelastic and differential scanning calorimetry properties of (PP/EPR)/EOC blends shows the incompatibility of the components even in presence of PP‐g‐MAH copolymer. POLYM. ENG. SCI., 47:1009–1015, 2007. © 2007 Society of Plastics Engineers

Morphologies and Rheological Properties of Ethylene-Propylene Block Copolymers

Ethylene-propylene block copolymer (EPBC) is mainly composed of two component polymers, polypropylene (PP) and ethylene-propylene rubber (EPR). The dependence of morphologies as well as dynamic moduli of EPBC on the molecular characteristics of the components were investigated for four EPBC samples. From the results of the temperature dependence of dynamic moduli and the morphologies, it was suggested that the samples have heterogeneous structure composed of a dispersed EPR phase and a PP matrix phase in which a part of the EPR component dissolves. The concentration of dissolved EPR in the matrix increases with increasing propylene content of the EPR component. For the melts of the EPBC samples containing the EPR component of higher than about 70 wt% propylene contents, a secondary plateau was observed in the long time region on the dynamic viscoelasticity curves. To clarify the origin of this slow relaxation, the dynamic viscoelasticity were compared with three theories: Palierne's emulsion model, the thermal diffusional model and the blending rule. The comparison suggested that the blending rule can well explain the secondary plateau behavior originated from the existence of the high molecular weight EPR dissolved in the PP matrix.

Local thermal degradation behavior of heterophasic polypropylene copolymers

Polypropylene (PP) impact copolymer is one of the heterophasic PP systems that is improved by rubber modification. Because the copolymer is a complicated polymer blend, which mainly consists of PP and ethylene–propylene rubber (EPR) components, the degradation behavior has hardly been studied. In this study, the thermal degradation of the copolymer was studied through direct observation by atomic force microscopy, which is a powerful tool for observing a local domain in a polymer blend. The degradation behavior was visually captured by the mapping of topological changes. Although the EPR phase was hardly degraded, the neighboring PP matrix was degraded selectively. The degradation behavior of the copolymer was found to be heterogeneous. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1831–1835, 2006

Study of local oxidative degradation in polypropylene impact copolymer by energy dispersive X-ray system

In this study, the thermal oxidative degradation of a polypropylene (PP) impact copolymer was examined using a transmission electron microscope equipped with an energy dispersive X-ray system (TEM/EDX). The oxidative behavior was visually captured by oxygen line analysis. The oxidation resistance of the ethylene-propylene rubber (EPR) phase was considerably higher than that of the PP matrix, indicating that the degradation behavior of the PP impact copolymer was heterogeneous. It was found that the higher resistance of the EPR phase originated from its primary structure by 13C-NMR measurement.

Effects of molecular weight of SEBS triblock copolymer on the morphology, impact strength, and rheological property of syndiotactic polystyrene/ethylene–propylene rubber blends

The effects of molecular weight of atactic polystyrene-b-poly(ethylene-co-butylene)-b-atactic polystyrene [SEBS] triblock copolymers on the morphology, impact strength, and rheological property of syndiotactic polystyrene (sPS)/ethylene–propylene rubber (EPR) blends are examined. From the morphological analysis, it is observed that the size of dispersed EPR phase in sPS/EPR/SEBS blends decreases and the particle size distribution becomes narrower with increasing amounts of SEBS in the blends. It is found that the low molecular weight SEBS is more effective in increasing the impact strength of sPS/EPR blend than the high molecular weight SEBS. The SEM micrographs after impact test show that the sPS/EPR blends compatibilized by the low molecular weight SEBS have a good adhesion between the sPS matrix and dispersed EPR particles, whereas the sPS/EPR blends compatibilized by the high molecular weight SEBS exhibit a poor adhesion between phases. Although the complex viscosity of low molecular weight SEBS is much lower than that of high molecular weight SEBS, the complex viscosity of the sPS/EPR blends compatibilized by the low molecular weight SEBS is higher than that of the sPS/EPR blends compatibilized by the high molecular weight SEBS. It is suggested from these results that the blocks in the low molecular weight SEBS penetrate into the corresponding phase more easily than the blocks in the high molecular weight SEBS.

Fracture toughness of multiphase polypropylene composites containing rubbery and particulate inclusions

The fracture toughness of binary and ternary phase polypropylene (PP) composites containing ethylene–propylene rubber (EPR) and glass beads, has been studied using the J-integral method at 23 and − 20 °C. For determining Jc, analysis of the stress-whitening zone was found to be more meaningful than the commonly used blunting line approach. Functionalized EPR was found to be more effective toughening additive for PP than EPR, in both binary and ternary phase compositions. Crack growth mechanisms were examined by scanning electron microscopy. In rubber-modified blends, cavitation and shear yielding were found to be the primary toughening mechanisms, while in ternary phase composites particle–matrix debonding played a major role.

Influence of heterogeneous textures of polypropylene/ethylene–propylene–rubber blends on dynamic viscoelastic properties in the solid

Heterogeneous textures in phase separated, solid polypropylene (PP)/ethylene–propylene–rubber (EPR) blends were investigated in relation to their dynamic viscoelastic properties. The glass transition temperature (Tg) of amorphous PP phase in PP/EPR blend quenched from molten state varies with propylene content of EPR as well as EPR content in blend. The Tg depends on the concentration of EPR dissolved in the amorphous PP phase. On the other hand, the Tg of EPR phase in PP/EPR blend is about the same as that of pure EPR. This fact means that PP molecules were not dissolved in EPR phase. For the same blending composition, the EPR concentration in matrix PP phase was larger for EPR having more propylene units. When the same EPR was used, the EPR concentration in the matrix was larger for blends with larger EPR content. The EPR concentration in the amorphous PP phase of PP/EPR blend in solid state is about the same as that in molten state, indicating that the EPR concentration in solid state was essentially determined by the EPR concentration in molten state.