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Volatile decomposition products of ultraviolet‐irradiated polyethylene, nylon, Mylar, and Acrilan have been analyzed. The principal decomposition products of polyethylene are hydrogen and methane. Besides hydrogen and methane, carbon monoxide occurs in considerable amounts in the decomposition products of the other polymers. There is a considerable difference in the relative abundances of methane and hydrogen in the decomposition products, depending on whether irradiation was performed in a vacuum or in nitrogen. Decomposition products of ultraviolet‐irradiated nylon include all of the primary amines from methyl through hexyl. Mechanisms consistent with the observed results of photolysis are proposed.

Ultraviolet irradiation of polyethylen, nylon, Mylar, and Acrilan produces higher scission‐to‐crosslinking ratios when irradiation is performed in a nitrogen atmosphere than it does when irradiation is in a vacuum. Irradiation of polyethylene in nitrogen causes a sharp decrease in molecular weight while irradiation of Acrilan in vacuum causes an equally notable increase in molecular weight.

Polyethylene, Teflon, nylon, Mylar, and Acrilan have been irradiated in vacuo and in an atmosphere of nitrogen with narrow bands of ultraviolet radiation centered at 244, 314, and 369 μ and with monochromatic ultraviolet light of wavelength 253.7 μ. The physical properties of all these polymers are ultimately degraded by ultraviolet light of any of these wavelengths, but the shorter wavelengths are much the more effective in producing changes. The degradation of polyethylene, nylon, Mylar, and Acrilan is faster when irradiation is in an inert atmosphere of nitrogen than it is when irradiation is in vacuo. Teflon, however, degrades more rapidly in vacuo than in a nitrogen atmosphere.

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