Poly(viny1 chloride)/Styrene-Butadiene Rubber Blends Prepared by Dynamic Vulcanization with Nitrile Rubber as the Compatibilizer S.-H. ZHU,' C.- zyxwvutsrq M. CHAN,',* zyxwvutsrqp and Y. X. ZHANCZ zyxwvuts 'Department of Chemical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; and 'Department of Applied Chemistry, Shanghai jiao Tong University, Shanghai 200240, People's Republic of China SYNOPSIS zyxwvutsrqponm A new kind of thermoplastic elastomer is obtained by dynamic curing of PVC/SBR blends. A compatibilizer is necessary, and of three tested-NBR and two ABSs-NBR-18 is the best. Sulfur and Dicumyl peroxide were chosen as the two different curing agents for the blends. The curing agent and its concentration have a dramatic effect on the mechanical properties. Di(2-ethyl hexy1)phthalate was used as the plasticizer for PVC. Variations in the PVC and di(2-ethyl hexy1)phthalate concentrations can produce materials having a wide range of hardness and strength to meet the needs of different applications. The effects of processing parameters such as blending time and processing temperature and the effect of filler in the blend on the mechanical properties were also investigated. The material, after processing five times, showed no significant changes in physical properties. zyxw 0 1995 John Wiley & Sons, Inc. INTRODUCTION Thermoplastic elastomers (TPEs) are a new class of thermoplastics of which the properties can be more easily tailored-more so than block copoly- mers-by simply changing the ratio of the rubber to plastic in the blend.'-'' These materials are phase-separated systems in which one phase is rubbery at room temperature and the other is hard and solid. They possess the elasticity of a rubber and the thermoplasticity of a plastic, yet retain unique features of its components such as better ultraviolet and ozone resistance, solvent resistance, and high deformation temperature compared to elastomers. As a result, many commercial TPEs have been developed for various applications. Gen- erally, it is easy to combine a rubber and a plastic of similar polarities and solubility parameters to produce a useful thermoplastic elastomer such as polypropylene (PP ) /ethylene-propylene-diene copolymer (EPDM ) , ~~~~~~ ~ ~~ * To whom correspondence should be addressed. Journal of Applied Polymer Science, Vol. 58,621-631 (1995) 0 1995 John Wiley & Sons, Inc. zyxwvutsrqponm CCC 0021-8995/95/030621-11 epoxidized natural rubber and poly (vinyl chloride), lo poly (vinyl chloride ) ( PVC ) /acrylonitrile-butadiene rubber (NBR) , ''J' and nylon/NBR.13 On the other hand, it is difficult to produce a TPE using a plastic and an elastomer having different polarities and sol- ubility parameters because of the high interfacial ten- sion. This problem can be resolved by the use of a compatibilizer to improve the interfacial adhesion be- tween the two phase^.'^^'^ One of the well-known miscible polymer blends is PVC/NBR. PVC/NBR blends have been used since 1940 in applications such as sealants, gaskets, valve disks, coatings for electric wires and cables, soles, hoses, footwear, and artificial leather, due to low cost and desirable properties such as ultraviolet and ozone resistance, tear resistance, thermal aging, and solvent resistance. Modifications of 70/30 (weight ratio) PVC/NBR blends using natural rubber (NR) and styrene-bu- tadiene rubber (SBR) have been attempted by George et a1.16Their results show that replacement of NBR by NR up to 15% (by weight) improves mechanical properties and decreases the cost of the blend. If SBR is used, NBR up to 30% can be re- zy 62 1