The chemical effects of photo-oxidation on isoprene rubber

✍ Scribed by M.A. Rodrigues; M.-A. De Paoli

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 600 KB
• Volume: 21
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(85)90058-8

✦ Synopsis

There has been a detailed study of the non-volatile products of the photo-oxidation of two kinds of cis-1,4-polyisoprene, viz. natural and synthetic (98% cis), by irradiating films in the solid state under ambient conditions. I.R., ~H-and 13C-NMR and chemical methods indicated the formation of the following functional groups: hydroperoxides, alcohols, ketones, aldehydes, epoxides and carboxylic acids. There is also evidence for the formation of esters and cthcrs. Viscomctric measurements showed that chain-scission predominates over cross-linking for irradiation of toluene solutions of the rubbers. Photo-oxidation kinetic measurements for films containing singlet oxygen quenchers, such as 1.2diazabicyclo[2,2,2]octane and diphenyl-p-isobenzofuran, showed that singlet oxygen is not responsible for the initiation of the environmental photo-oxidation of cis-1.4-polyisoprene. Increasing the number of successive coagulation steps, in the purification of natural rubber, decreased its stability, confirming the presence of an intrinsic natural stabilizer. Synthetic isoprene rubber showed less stability than natural rubber.