IMPROVING THE PROPERTIES OF A POLY (ACRYLONITRILE-CO-BUTADIENE)/NATURAL RUBBER BLEND BY INTRODUCING INTERFACIAL CROSSLINKS USING BISMALEIMIDE DURING THE INITIAL PHASE OF ACCELERATED SULFUR CURING

ABSTRACT To develop a technologically compatible blend of natural rubber (NR) and acrylonitrile-co-butadiene rubber (NBR) is always a challenge due to their polarity mismatch. As a result, the physico-mechanical properties of their blends will be generally poor. To address this issue, an attempt was made to increase the uniform distribution of crosslinks across the blend phases at the time of molding at 170 °C. A cure composition consisting of sulfur (S) and a delayed-action accelerator (N-cyclohexyl-2-benzothiazole sulfenamide: CBS) has been designed to co-crosslink both phases of the blend simultaneously. The tensile properties, particularly the tensile strength (TS) of the blend cured by this method were superior (approximately 371% greater) than the TS of the blend cured using a combination of S/CBS and an ultrafast accelerator (Tetramethylthiuram disulfide, TMTD). A bifunctional maleimide (Maleide F) was also employed in conjunction with S/CBS in the curing recipe to further improve the distribution of sulfidic crosslinks by reducing the interfacial tension between the NR and NBR phases via Alder-ene reaction.