Characterization of photodegradation of polybutadiene and polyisoprene:: chronology of crosslinking and chain-scission

Photodegradation of polybutadiene, styrene-butadiene copolymer, natural and synthetic polyisoprene was studied, under accelerated photo-oxidative conditions, using FT-IR spectroscopy, densitometry and thermoporosimetry. The behaviours of these elastomers were compared with respect to their ability to generate oxidized species, leading to chain-scissions, and in contrast their ability to undergo crosslinking reactions. It was found that the polybutadiene-based elastomers are more sensitive to crosslinking phenomena than polyisoprene. It was observed that polybutadiene undergoes crosslinking reactions early and before the formation of oxidized products, whereas polyisoprene has an induction period (10-20 h) during which no crosslinking is detected despite the formation of carbonyl groups. (c) 2004 Elsevier Ltd. All rights reserved.