Poly(vinyl alcohol) was used as base material for hydrogel preparation. The water absorption, gel fraction, and density of different gels prepared by the freezing/thawing method were studied.

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SynopsisIf wood under clear, ultraviolet-transparent coatings could be protected from photodegradation, the performance of clear finishes would be greatly enhanced. The objective of this study was to determine whether acetylation or methylation of the wood and whether reaction with phenylhydrazine or treatment with acid copper chromate would impart resistance to photodegradation by longwave UV light. Infrared (IR) and ultraviolet (UV) spectra, analysis of wood before and after irradiation, and quantitative determination of volatile degradation products were used to measure degradation. Acetylation did not protect wood, although acetyl groups themselves were resistant to photodegradation. Methylation did not protect wood either, and methylated wood yielded more methanol and formaldehyde during photodegradation. Phenylhydrazine-modified wood lost the newly introduced nitrogen and failed to protect wood also. Acid copper chromate treatment allowed some demethoxylation, hut severely curtailed the photooxidation process.

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