ABSTRACT This article discusses some properties such as tensile properties, chemical and oil resistance, gel content, crystallinity, and morphology of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends. Dicumyl peroxide (DCP) was applied as a crosslinking agent. In terms of tensile properties, peroxide vulcanized blend shows higher tensile strength and tensile modulus (stress at 100% elongation, M100) as compared with the unvulcanized blend. The elongation at break of the peroxide vulcanized blend is higher for the blend with NR rich content compared with the EPDM rich content. The improvements in chemical and oil resistance as well as gel content of peroxide vulcanized blends have also proved the formation of crosslinks in the rubber phase. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the crosslinks have occurred during dynamic vulcanization. Dynamical vulcanization with DCP has decreased the percent crystallinity of blends that can be attributed to the formation of crosslinks in the rubber. 相似文献
The effects of glass bead filler content and surface treatment of the glass with a silane coupling agent on the room temperature impact fracture behavior of polypropylene (PP)/ethylene‐propylene‐diene monomer copolymer (EPDM)/glass bead(GB) ternary composites were determined. The volume fraction of EPDM was kept constant at 10%. The impact fracture energy and impact strength of the composites increased with increasing volume fraction of glass beads (?g). Surface pretreatment of the glass beads had an insignificant effect on the impact behavior. For a fixed filler content, the best impact strength was achieved when untreated glass beads and a maleic anhydride modified EPDM were used. The impact strength exhibited a maximum value at ?g=15%. Morphology/impact property relationships and an explanation of the toughening mechanisms were developed by comparing the impact properties with scanning electron micrographs of fracture surfaces. 相似文献
Reactive blending of the rubber EPDM (a terpolymer consisting of ethylene, propylene and a diene) and the thermoplastic material SAN (a copolymer of styrene and acrylonitrile) is reinvestigated with special attention to EPDM/SAN blends with a 50/50 blend ratio. A resin cure system based on a low molecular weight phenol formaldehyde condensate, which primarily consists of dimethylolphenol and stannous dichloride, is used for compatibilization of EPDM and SAN, as well as for crosslinking of the EPDM phase. The amounts of phenolic resin and SnCl2 · 2H2O as well as the EPDM grade and the EPDM/SAN blend ratio are varied. The blends are characterized by stress‐strain measurements, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Unreacted EPDM, unreacted SAN and gel plus graft copolymer are quantitatively determined by fractionation of the blends with a binary solvent mixture which exhibits phase separation at room temperature. Blends prepared from EPDM grades that are amorphous and have a high molar mass exhibit high levels of gel and rather poor mechanical properties. With these blends, gel formation is favored over the formation of EPDM/SAN graft copolymers. Even with low levels of the resin cure system, the formation of gel cannot be avoided. It is therefore not possible to prepare graft copolymers without some gelling. Blends prepared from an EPDM grade with high crystallinity and a low Mooney viscosity exhibit substantially better mechanical properties than blends based on amorphous and higher viscosity EPDM grades. TEM and SEM micrographs reveal good dispersion of the two polymers, as well as good interfacial adhesion between the EPDM and the SAN phase. This electron microscopic evidence, in combination with low gel contents, supports the view that the tendency towards graft copolymer formation and gelling strongly depends on the EPDM grade used. Variation of the EPDM/SAN blend ratio between 5–90 wt.‐% results in blends which cover the product range from toughened thermoplastics to thermoplastic elastomers.
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. 相似文献
The effects of dynamic vulcanization on the process development and some properties, such as tensile properties, swelling index, gel content, crystallinity, and morphology, of the polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends were investigated. Dynamically vulcanized blends show higher stabilization torque than unvulcanized blends. In terms of tensile properties, the tensile strength and tensile modulus (stress at 100% elongation, M100) of the vulcanized blends have been found to increase as compared with the unvulcanized blends, whereas the elongation at break is higher in the blend with richer EPDM content. These results can be attributed to the formation of cross-linking in the rubber phase. The formation of cross-links in the rubber phase has also been proved by swelling index and gel content. The percentage of crystallinity of the blends is decreased by dynamic vulcanization. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the cross-links occurred during dynamic vulcanization. 相似文献
The mechanical properties and crystal morphological structures of dynamically photocrosslinked polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) blends have been studied by mechanical tests, wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Dynamically photocrosslinking of PP/EPDM blends can improve the mechanical propertiess considerably, especially the notched Izod impact strength at low temperature. Data obtained from mechanical tests show that the notched Izod impact strength of a dynamically photocrosslinked sample with 30% EPDM at ?20°C is about six times that of an uncrosslinked sample with the same EPDM component. The results from the WAXD, SEM, and DSC measurements reveal the enhanced mechanism of impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (i) the β‐type crystal structure of PP is formed and the interplanar distance of β‐type crystal increases slightly with an increase in the EPDM component; (ii) the droplet size of the EPDM phase in the photocrosslinked PP/EPDM blends is obviously reduced and the droplet number is increased with an increase in the EPDM component during the dynamical photocrosslinking process; (iii) the graft copolymer of PP‐g‐EPDM is formed at the interface between PP and EPDM components. All the above changes from the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of PP/EPDM blends at low temperatures. 相似文献