The kinetics of the photodegradation were examined, and the quantum yield of the various processes involved were evaluated in an effort to improve light stability. The photodegradation was monitored by changes in the ultraviolet and infrared absorption spectra, oxygen uptake, and volatile products measurements. These highly cross-linked networks were much more resistant to weathering than related linear polymers. Atmospheric oxygen had a markedly detrimental effect on the durability. Pyrex-filtered light reduced the rate of photooxidation. A benzotriazole ultraviolet absorber enhanced light stability. -- AATA