PHOTOOXIDATION OF POLYBUTADIENE AT LONG WAVELENGTHS (LAMBDA-GREATER-THAN-300NM)

Polybutadiene (BR) films were exposed to radiation of long wavelength (lambda>300 nm). Products resulting from the photooxidation of BR have been identified using various techniques such as FTIR and UV spectros copy, and chemical derivatisation reactions. The decrease of permeabil ity to oxygen of BR films during irradiation makes it necessary to stu dy the vacuum photothermal decomposition of hydroperoxides that are th e primary oxidation products. Results show that two successive steps a re involved in the transformation of BR films on irradiation. In the f irst stage, when oxygen can diffuse through the irradiated film, photo oxidation reactions occur implying the formation of hydroperoxides, al pha,beta-unsaturated species and final saturated carboxylic acid group s. In the second stage, when the diffusion of oxygen through the surfa ce layer is no longer possible because of crosslinking, photolysis rea ctions of photooxidation products account for the formation of the fin al products observed. (C) 1996 Elsevier Science Limited.