AbstractThe chemical, physical, and mechanical changes in the surface properties of poly‐(ethylene terephthalate) film produced by ultraviolet light have been examined. Attenuated total reflection infrared spectroscopy has indicated that numerous chemical scission reactions occur in the front surface layer facing the source of irradiation, resulting in the formation of carboxylic acid endgroups. This preferential surface phtodegradation has been confirmed by examining the cross section of irradiated film by electron beam‐induced luminescence. Conventional electron microscopy revealed little changes in the surface appearance of irradiated film. However, indirect techniques were devised which indicated that changes do occur in the physical properties of the surface. These observed changes are believed to be responsible for the decrease in film tensile strength, which has been shown to be a surface phenomenon and not a bulk prope
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