Photothermal Degradation of Ethylene/Vinylacetate Copolymer

Abstract

Ethylene/vinyl acetate copolymer (EVA), which has desirable elastomeric properties, low material cost and easy processability, is being considered as a candidate encapsulation material for photovoltaic modules. However, without protection from UV irradiation, EVA is expected to undergo photodegradation similar to that encountered in polyethylene and polyvinylacetate· We have carried out photothermal degradation studies of a “stabilized” formulation of EVA in the temperature range of 25°C to lO5°C under different oxygen environments. At low temperature (25°C), slow photooxidation occurred via electronic energy transfer involving the UV absorber incorporated in the polymer. But no change in physical properties of the bulk polymer can be detected up to 1500 hours of irradiation. At elevated temperature, leaching/evaporation of additives took place leading ultimately to chemical crosslinking of the co-polymer and formation of volatile photoproducts such as acetic acid.