Comparative analysis of delayed‐onset peroxide crosslinking formulations

Strategies for affecting the onset and yield of peroxide‐initiated polymer crosslinking formulations are demonstrated and discussed in terms of underlying reaction mechanisms. Rheological studies of linear low density polyethylene (LLDPE) crosslinking by dicumyl peroxide show that conventional antioxidants such as 3,5‐di‐tert‐4‐butylhydroxytoluene and 2,2,6,6‐tetramethyl‐1‐piperidinyloxy, as well as reported scorch protectants such as 2,4‐diphenyl‐4‐methyl pentene and 1,1‐diphenylethylene, lower crosslinking rates while suppressing the ultimate state of cure. In contrast, the acrylated nitroxyl, 4‐acryloyloxy‐2,2,6,6‐tetramethylpiperidine‐N‐oxyl (AOTEMPO) is shown to suppress the onset of LLDPE crosslinking entirely, while having little effect on the thermoset's final storage modulus. Moreover, AOTEMPO proved capable of quenching allylic macroradical intermediates in cis‐1,4‐polyisoprene cure formulations, whereas other classes of scorch protecting additives had little effect on crosslinking dynamics and yields. POLYM. ENG. SCI., 54:2645–2653, 2014.