Photodegradation of Polymers - Physical Characteristics and Applications

Abstract

Abstract Photodegradation of polymers is generally accepted as the main factor that limits their use in outdoor applications. It is caused by the ultraviolet (UV) component of solar radiation and is a serious problem in the sunniest climates. Photo-oxidation creates free radicals that start a chain reaction that can progress quite rapidly, causing rapid deterioration of mechanical properties. The chemical and physical mechanisms of degradation and their effects on engineering properties and morphological changes (such as secondary crystallization) are discussed. Photostabilizers that can produce spectacular improvements in polymer lifetime under UV exposure are discussed. Testing for photodegradability is dealt with. It usually involves accelerated laboratory conditioning and this is difficult to calibrate against natural conditions to produce lifetime prediction. Photodegradation products are often prodegradants placing restrictions on the recyclability,which is also discussed.