THE USE OF EVA-CONTAINING MERCAPTO GROUPS IN NATURAL-RUBBER EVA BLENDS .2. THE EFFECT OF CURING SYSTEM ON MECHANICAL AND THERMAL-PROPERTIESOF THE BLENDS

Natural rubber (NR)-poly(ethylene-co-vinyl acetate) (EVA) blends have been studied by incorporation of mercapto-modified EVA (EVASH) combine d with dicumyl peroxide (DCP) as a curing agent. The mechanical, therm al, and morphological properties of NR-EVA blends as functions of blen d composition and compatibilizer and/or curative additions were invest igated. An EVASH-DCP combined system leads to the greatest improvement in tensile strength when EVA is dispersed within the NR matrix. Highe r performance on Shore A hardness was also achieved with this combined system. For blends characterized by NR domains dispersed in the EVA m atrix, the efficiency of pure DCP in improving the tensile strength is higher. Morphological observations and selective extraction experimen ts indicate the cross-linking of NR phase in both systems. A cross-lin king of the EVA phase is also suggested by DCP or an EVASH-DCP combine d system, based on the decreasing degree of crystallinity of this phas e. (C) 1996 John Wiley & Sons, Inc.