The compatibilization of SBR/EVA by mercapto-modified EVA

Styrene-butadiene copolymer/ethylene-vinyl acetate copolymer (SBR/EVA) blen ds with different ratios were prepared by using a Haake internal mixer. The se blends were compatibilized with mercapto-modified EVA (EVALSH), which pr omotes bonding between the SBR phase and the EVALSH through a chemical reac tion between the mercapto groups of the reactive compatibilizing agent and the double bond of the unsaturated rubber. The presence of EVALSH resulted in an improvement of the tensile strength of the unvulcanized SBR/EVA blend s and also a more uniform dispersion of the EVA phase inside the SBR matrix for blends containing higher amount of the rubber phase. The formation of insoluble material in the blends containing EVALSH indicates reactive compa tibilization, which was confirmed by Fourier transform infrared analysis an d also by dynamic mechanical analysis. In this case, a decrease in damping properties of the SBR phase was observed as a consequence of decreasing cha in mobility. EVALSH also caused a decrease in degree of crystallinity of th e EVA phase as observed by differential scanning calorimetry analysis. (C) 2001 Elsevier Science Ltd. AH rights reserved.