Chapter 9 - Degradation of Polymers

Abstract

This chapter focuses on approaches employed for the degradation of polymers. Environmental pollution by synthetic polymers, such as waste plastics and water-soluble synthetic polymers in wastewater has been recognized as a major problem. Degradation of polymers can be carried out by heat, radiation, or biochemical treatment. The radiant energy may be high-energy radiation from gamma rays, ion beams, and electrons or even low-energy radiation from ultraviolet (UV) light. UV stabilizers added to polymer products reduce the rate of degradation. Chemical degradation results from treatment with chemicals such as acids and alkalis. Biodegradation of polymers results from the use of microorganisms and enzymes. Since most of the polymers are resistant to degradation, research over the past several years has focused on developing biodegradable polymers that are degraded and ultimately catabolized to carbon dioxide and water by bacteria and fungi under natural conditions. During the degradation process, they should not generate any substances that are harmful. These polymers can be classified into three major categories: polyesters produced by microorganisms, natural polysaccharides and other biopolymers like starch, and synthetic polymers like aliphatic polymers. Another approach toward achieving biodegradability has been through the addition of biodegradable groups into the main chain during the production of industrial polymers prepared by free radical copolymerization. Two such approaches are the use of ethylene bis(mercaptoacetate) as a chain transfer agent during the copolymerization of styrene and MMA, and the preparation of copolymers of vinylic monomers with cyclic comonomers containing the biodegradable functions such as ketene acetal and cyclic disulfides.