ABSTRACT
The deterioration of a polymeric material depends on how and to what extent it interacts with its surroundings. Outdoor uses of plastic products include buildings and construction, agriculture and horticulture, automobiles and airplanes, solar heating equipment, and packaging. It has been estimated that roughly half the annual tonnage of polymer is employed outdoors (1), where performance is often limited by weathering. Degradation of plastics during outdoor exposure is influenced to varying degrees by all natural meteorological phenomena. Heat, radiation (ultraviolet and infrared), rain, humidity, atmospheric contaminants, thermal cycling, and oxygen content of air, all contribute to the degradation of plastics subjected to outdoor exposure. None of these factors are constant in anyone location, and weather conditions vary widely with location. The useful lifetime of plastics needs to be predicted for planning their maintenance and replacement. To attain maximum accuracy in predicting the useful lifetime of an outdoor exposed plastic, all components of the anticipated exposure environment must be considered. This is best accomplished by conducting exposure trials in that environment (2).
