Continuous Devulcanization by Shear Flow Stage Reaction Control Technology for Rubber Recycling, Part 7: Morphology and Mechanical Properties of Polypropylene/Reclaimed EPDM Rubber Blend

Blend of polypropylene and reclaimed EPDM (ethylene-propylene-diene terpolymer) rubber was studied as one of the method of recycling of the reclaimed rubber. The reclaimed EPDM rubber was obtained from vulcanized rubber by devulcanization using shear flow stage reactor proposed in our previous paper. The dispersion of the reclaimed rubber in polypropylene resin matrix strongly depended on the degree of residual crosslinking density of the reclaimed rubber. The optimum value of the residual crosslinking density of the reclaimed rubber for fine dispersion was about one tenth of that of the original vulcanized EPDM rubber used. The size of reclaimed rubber particle in polypropylene matrix became sub-micron. The value was as same as that of rubber particle in blend which was made of polypropylene and new raw EPDM rubber. Izod impact strength of the blend increased with decreasing of residual crosslinking density of the reclaimed rubber. Maximum izod impact strength of the blend was about two times of that of polypropylene/raw EPDM rubber blend. It was found that the reclaimed EPDM rubber which has a suitable residual crosslinking density and carbon black as a filler is effective as a impact modifier of polypropylene resin comparing with raw EPDM rubber.