The photochemistry of polyurethanes has been of interest to academics and in the area of coatings. Relatively little workhas been done on polyurethane foams, apart from numerous patents or a few papers teaching means to minimize the surfaceyellowing, has been reported for polyurethane foams. It is generally accepted that exposure to visible light has minimalimpact on the physical properties of foam. The application of modern statistical methods to some recent observations inseveral labs has demonstrated that exposure to light can affect the variability of some physical property test results.Increasing exposure time and/or light intensity during the storage of foam samples under ambient laboratory conditionsincreases the amount of permanent set induced in some compression set tests. Variability resulted from uncontrolled lightexposure of cut samples prior to being compressed. Other foam properties are not substantively affected. All types offlexible foam can react in a similar manner. This paper will describe the experiments and data which demonstrate the abovephenomena, some theories about the mechanism of the effect and recommendations to decrease the variability of foamtesting.
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