关键词: 聚乙烯醇, 流变性能, 结构异质性, 力学性能, 耐水性能

Abstract:

There is structural heterogeneity in polyvinyl alcohol (PVA) films prepared by solvent evaporation. In this study, PVA with molecular weights (M_w) of 27000, 47000, 75000 and 98000 were used for experiments. It was focused on the process of formation, structure and properties of PVA films, and the influence of polymerization degree (DP) on the rheological properties, structural homogeneity, hygroscopic and water-resistant properties of the PVA films, as well as its mechanical properties and optical properties were investigated. The results showed that with the increase of DP, the required concentration for liquid-solid transformation of PVA aqueous solution decreased and the structural heterogeneity of PVA films in the longitudinal section also decreased. Besides, the contact angle of PVA film increased with the increase of DP, which was attributed to the decrease of surface roughness. PVA-1 (M_w≈27000), the lowest DP, had the highest sensitivity to moisture and the worst water resistance. Both the DP and the moisture content indicated the significant impact on the mechanical properties of PVA film. When the moisture content reached to 5%, the yield point just disappeared, resulting in the obvious stress whitening phenomenon during the tensile process. It was attributed to the water in the PVA film which was treated as a stress concentration point during loading, resulting in micropores formation.

Key words: polyvinyl alcohol, rheological property, structural heterogeneity, mechanical property, water resistance