engleski

Influence of the Physical State on the Ultraviolet Degradation of Poly(Vinyl Alcohol)

The course of photodegradation, photocrosslinking and photooxidation reactions of poly(vinyl alcohol), PVA, was studied both in solutions and in the form of solid film. The influence of the irradiation dose as well as the molecular mass and degree of hydrolysis of PVA was established. Changes produced by irradiation were followed by determining the viscosity changes and by spectrophotometric measurements. It was found that the intensities of photodegradation, photocrosslinking and photooxidation depend on the physical state of PVA. Dissolved PVA undergose crosslinking reactions and the formation of polymeric gels is readily observed if a sufficient irradiation dose has been applied. The PVA samples of high molecular mass as well as those of low degrees of hydrolysis are highly susceptible to gel formation. The oxidation of PVA is not observed until the gel is formed. Under a sufficient irradiation dose the films are oxidized to such an extent that carbonyl groups and double bonds appear in the polymeric chains. The degradation of PVA is more pronounced in high molecular mass samples as well as on samples with lower degrees of hydrolysis.

poly(vinyl alcohol); photocrosslinking; molecular mass; physical state; photodegradation; photocrosslinking; oxidation

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