Gel Formation in Polyvinyl Alcohol Film by Heat Treatment after Exposure to Ultra-violet Light

The physical properties of polyvinyl alcohol are found to be changed by exposure to ultra-violet light followed by heat treatment as in the case of high energy radiations. When polyvinyl alcohol is irradiated in air by ultra-violet light, carbonyl groups are produced. The heat treatment of irradiated polyvinyl alcohol above 120°C in a silicone oil bath produces crosslinkages between molecular chains.