Increasing the strength and water resistance of materials based on poly-vinyl alcohol with boric acid

Polyvinyl alcohol (PVA) is a promising polymer for the production of materials with desired properties, primarily water solubility and biodegradability. The main reason for limiting the use of film materials based on PVA is the lack of a mechanism for regulating the rate of their dissolution. Purpose of work: evaluation of the strength characteristics and water resistance of PVA films and PVA:MC composites when crosslinked with boric acid, depending on the amount of borate introduced into the polymer matrix. The objects of the study were 8 experimental samples: No. 1 - a film of unmodified PVA grade KurarayPoval 3-83, plasticized with glycerin, obtained by pouring from a 5% solution; No. 2-4 - PVA films modified with boric acid in various amounts, obtained similarly to sample No. 1; No. 5 - a plate of PVA:MC composite (50:50 wt.%), obtained by liquid-phase combination of PVA unmodified with boric acid and microcellulose dispersion, followed by dehydration in air; No. 6-8 - plates of the PVA:MC composite (50:50 wt.%), obtained on the basis of PVA modified with various amounts of boric acid, similarly to sample No. 5. As a result of the study, it was found that the modification ("crosslinking") of PVA grade KurarayPoval 3-83 with boric acid is accompanied by an increase in the viscosity of PVA (which manifests itself in the clouding of the films during dehydration), an increase in strength indicators in proportion to the amount of borate ion introduced into the PVA polymer matrix, but at At the same time, the water resistance of the modified PVA films increases to a certain limit of the borate content (in particular, with the introduction of 0.075 and 0.15 ml of boric acid per 1 ml of PVA, the films did not dissolve within 1 week of exposure to water at t = 20 °C, but with the introduction of 0.30 ml of boric acid per 1 ml of PVA, the film dissolved in 3 hours of exposure, for comparison, unmodified PVA of the specified brand dissolves in water at n.o. for 10 minutes).