The compatibilization of SBR/EVA by mercapto-modified EVA

Styrene–butadiene copolymer/ethylene–vinyl acetate copolymer (SBR/EVA) blends with different ratios were prepared by using a Haake internal mixer. These blends were compatibilized with mercapto-modified EVA (EVALSH), which promotes bonding between the SBR phase and the EVALSH through a chemical reaction 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 blends 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 compatibilization, which was confirmed by Fourier transform infrared analysis and also by dynamic mechanical analysis. In this case, a decrease in damping properties of the SBR phase was observed as a consequence of decreasing chain mobility. EVALSH also caused a decrease in degree of crystallinity of the EVA phase as observed by differential scanning calorimetry analysis.