LIQUID RUBBER AS A REACTIVE SOFTENER FOR 1-CHLOROBUTADIENE-BUTADIENE RUBBER

Blending of hydroxyl-terminated liquid butadiene rubber (HT-BR) with 1 -chlorobutadiene-butadiene rubber (CB-BR) was carried out in the prese nce of isopropylidenedicyclohexyl diisocianate (IPCI) or sulfur as a c uring agent. It was found that the HT-BR/CB-BR blend displayed a good plasticity, i.e., its Mooney viscosity became lower than that of CB-BR , which brought about a good processability. The HT-BR fraction (E(S)) from the HT-BR/CB-BR blend vulcanizates, which was prepared by the IP CI-cured system, was evaluated to be ca. 20% by the equilibrium swelli ng test in benzene. The E(S) of the sulfur-cured blend was ca. 70%. Th is result shows that HT-BR acted as a reactive softener when it was co mpounded with CB-BR by curing with the diisocyanate. The tensile stren gth of the IPCI vulcanizate was exceedingly higher than that of sulfur -cured vulcanizate at all blend ratios of HT-BR to CB-BR. (C) 1996 Joh n Wiley & Sons, Inc.