POLYVINYL ALCOHOL

a colourless, water-soluble, flammable resin belonging to the family of organic polymers. The resin is used in sizing agents that confer resistance to oils and greases upon paper and textiles, to make films resistant to attack by solvents or oxygen, as a component of adhesives and emulsifiers, and as a starting material for the preparation of other resins. Polyvinyl alcohol is made by treating polyvinyl acetate (q.v.) with acids or alkalies, which remove the acetate groups without disrupting the long-chain structure of the molecule. If this reaction is allowed to proceed to completion, the product is highly soluble in water and insoluble in practically all organic solvents. Incomplete removal of the acetate groups yields resins less soluble in water and more soluble in certain organic liquids. The chemical properties of polyvinyl alcohol resemble those of simpler alcohols; the reactions with aldehydes are particularly useful in the preparation of additional resinous substances. Polyvinyl formal, made by the reaction with formaldehyde, and polyvinyl acetal, from acetaldehyde, are employed in making lacquers, coatings, and films; polyvinyl butyral, from butyraldehyde, is produced as a tough, clear, adhesive, and water-resistant film widely used in laminating glass to make it shatterproof (safety glass) and for similar applications.