Crosslink density distributions in NR BR blends: Effect of cure temperature and time

Crosslink distributions in gum natural rubber (NR)/cis-poly(butadiene) (BR) blend vulcanizates have been studied previously for cure states ranging from times shortly after the onset of cure to over-cure at 150 and 175 degrees C, respectively. The effects of lower cure temperatures on the crosslink distributions through the cure in NR/BR blend vulcanizates are considered here. The results of this and the previous work indicate that at temperatures above 140 degrees C the BR phase in gum NR/BR blends begins curing before and at a faster initial rate than the NR phase. Below 140 degrees C it is the NR phase which attains high crosslink densities first and maintains this increased level over BR until over-cure. The effect of cure temperature on crosslink distribution at maximum state of cure is also presented.