This article describes the processes involved in photochemical aging and weathering of polymeric materials. It explains how solar radiation, especially in the UV range, combines with atmospheric oxygen, driving photooxidation and the development of unstable photoproducts that cause various types of damage when they decompose, including the scission of carbon bonds and polymer chains. The article illustrates some of the degradation reactions that occur in different polymers and presents an overview of the strategies used to prevent such reactions or otherwise mitigate their effects.

This article describes weathering and environmental factors that contribute to degradation in plastics, including temperature variations, moisture, sunlight, oxidation, microbiologic attack, and other environmental elements. It presents a general overview of aging factors, their effects on plastic materials, and the accelerated test methods that can be used to estimate the reaction of a plastic component during actual use. The article focuses on the determination of service temperature as it indicates the ability of a material to retain a certain property, when exposed to elevated temperatures for an extended period of time. It concludes by describing various degradation processes, namely, thermal degradation, thermal oxidative degradation, photooxidative degradation, environmental corrosion, and chemical corrosion and discussing the ways of detecting these degradation processes.