The Structure And Properties Of EPDM/PP-TPV

The ethylene–propylene–diene terpolymer/polypropylene thermoplastic vulcanizate(EPDM/PP-TPV) was prepared in two-step process. The influence of technological conditions and formulation composition on dynamic vulcanization rate and mechanical performance of EPDM/PP-TPV was investigated. The impact of LEPDM on the dynamic vulcanization rate of EPDM/PP-TPV was studied by researching the vulcanizing kinetics. The dynamic rheological behavior of EPDM/PP-TPV was investigated in small strain rate region, the phase separation behavior and phase inversion phenomenon were studied by rotational rheometer. This article focuses on the influence of naphthenic oil, ratio of rubber to plastic, and rotational speed on the morphology structure and rheological property of EPDM/PP-TPV. All research results of this paper are described as follows.The dynamic vulcanization process of EPDM/PP-TPV contains two first-order kinetics reactions. The reaction activation energy of thermal curing process and flat curing process were 54.157 k J/mol and 62.959 k J/mol when LEPDM was not added. The reaction activation energy of thermal curing process and flat curing process were improved to be 116.934 k J/mol and 138.556 k J/mol when the content of LEPDM was 50 wt.%. The dynamic vulcanization process was significantly delayed after the addition of LEPDM.It is very significant to control the dynamic vulcanization rate of EPDM/PP-TPV to expand the sulfide window, then the study of phase behavior in the process of dynamic vulcanization can be achieved. The results showed that dynamic vulcanization rate of EPDM/PP-TPV increased because of growing temperature, improving rotational speed and declining content of naphthenic oil. The optimum technological conditions was determined by establish relationships between dynamic vulcanization rate and mechanical properties of EPDM/PP-TPV. The optimum technological conditions was as following:the temperature is 190 ℃, the rotational speed is 50 r?min-1, the content of naphthenic oil is 30 wt%, the content of DCP is 0.4 wt.%, and the ratio of rubber to plastic is 70/30, in this condition, the tensile strength of EPDM/PP-TPV was 14.36 MPa, the elongation at break was 468 %, the tear strength was 63.57 N/m, and the shore A hardness was 91 HA.In order to study the compatibility between EPDM and PP, the phase separation behavior of EPDM/PP-TPV was investigated with rotational rheometer. The results showed that phase separation phenomenon was observed when the content of EPDM was 10 wt.%, the co-continuous structure of EPDM/PP-TPV was formed when the content of EPDM was 70 wt.%.Morphology structure of EPDM/PP-TPV was investigated with scanning electron microscope and rotational rheometer. The results showed that morphology structure of EPDM/PP-TPV was strongly influenced by the content of naphthenic oil. The ratio of rubber to plastic had obvious regulating effect on the morphology structure of EPDM/PP blends, however, no severe regulating effect was observed in dynamic vulcanization system. The rotational speed had no significant effect on the phase distributions of EPDM/PP-TPV, crosslinked EPDM particles reached a minimum when the rotational speed was 50 r?min-1.The crystallization temperature and crystallinity of EPDM/PP-TPV decreased because of growing content of EPDM. In the process of the crystallization of PP, molecular chain of EPDM was not involved in the crystallization process, EPDM just play the role of heterogeneous nucleation. The crystal type of PP was not changed, both α-type crystals.The oil-resistant property of EPDM was much less than PP, the thermal aging property of EPDM was much better than PP. With the content of EPDM increased, the oil-resistant property of EPDM/PP-TPV reduced, and the thermal aging property of EPDM/PP-TPV improved. With the content of DCP increased, the oil-resistant property of EPDM/PP-TPV improved, and the thermal aging property of EPDM/PP-TPV reduced, the oil-resistant property of EPDM/PP-TPV tended to be stable when the content of DCP exceeded 0.4 wt.%. Appropriate rotational speed optimized the dispersion degree of the system, the oil-resistant property and the thermal aging property of EPDM/PP-TPV were optimized when the rotational speed was 50 r?min-1.