polyvinylalcohol

Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer obtained by hydrolysis of polyvinyl acetate. Its repeating unit is -CH2-CHOH-, and the degree of hydrolysis can vary widely (typically 87–99%). The hydrolysis level governs solubility and physical properties: highly hydrolyzed grades are more water soluble, while lower hydrolysis yields partial acetylation and different solubility behavior.

Production and structure

PVA is produced by converting polyvinyl acetate to polyvinyl alcohol under alkaline conditions, often using methanol as a solvent and sodium hydroxide as a catalyst. The resulting material can be tailored by controlling molecular weight and hydrolysis degree, producing a range of viscosities and film-forming abilities suitable for different applications.

Properties

PVA exhibits strong film-forming, adhesive, and binding properties with good transparency and mechanical strength. It is inherently water-soluble (especially highly hydrolyzed grades) and thermally stable enough for many processing methods, though it is not generally melt-processed like polyolefins. The polymer is typically non-toxic and can form blends and crosslinked networks (for example, using borax) to modify solubility and stiffness.

Applications

Common uses include papermaking and paper coatings, textile sizing, adhesives and binders for wood, ceramics, and coatings, and as a protective colloid in emulsions. It is also used in cosmetics and in certain food-contact coatings. In additive manufacturing, PVA serves as a water-soluble support material for some 3D printing processes. Its compatibility with water and moderate chemical resistance make it versatile for various coatings and binders.

Safety and environmental aspects

PVA is regarded as low-toxicity and relatively environmentally benign under normal use. It is water-soluble and biodegradable under appropriate microbial conditions, though rates vary with grade and environmental conditions.