"Carboxylated nitrile rubber with high strength and toughness based on metal coordination bonds from tetravalent zirconium cation and carboxyl group"

Based on the coordination interaction between carboxyl group of carboxylated nitrile rubber (XNBR) and Zr4+ from ZrOCl2·H2O, after XNBR was blended with ZrOCl2·H2O, sulfur and other cu-ring agents followed by hot-pressing, XNBR with high strength and toughness was prepared. The results showed that Zr4+-carboxyl group metal coordination bonds formed in the XNBR network crosslinked with sulfur. The tensile strength, modulus at 300% and fracture energy of the vulcanizates were significantly improved with the increase in the addition amount of ZrOCl2·H2O, and when the mole ratio of Zr4+ to carboxyl group of XNBR was 1/8, tensile strength, modulus at 300%, and fracture energy of the vulcanizate were 250%, 400% and 250% of the vulcanizate without Zr4+. The reason was mainly that when the vulcanizate was stretched, Zr4+-carboxyl group metal coordination bond as weak bond would break prior to the covalent bond, and during this process enormous energy was dissipated and therefore tensile strength and toughness of the vulcanizate improved.