Properties of Polyvinyl Acetal

The adhesive strength of polyvinyl acetal/phenolic adhesives cannot properly be considered without having regard to component ratio. It is, for example, commonly believed that increasing the acetal ratio (beyond some arbitrary limit) decreases tensile shear strength at elevated temperatures. To a certain extent this is true, but the presence of residual solvents, the inherent properties of the phenolic resin together with completeness of its cure, are other parameters that must be taken into consideration.

Polyvinyl Acetal/Phenolic Resin Adhesives

The term phenolic resin means a resin derived from formaldehyde and phenol itself. The most important polyvinyl acetals are the butyral and formal. The name polyvinyl acetal is more specifically applied to the product of reaction with acetaldehyde, but this acetal is not important as a component in two polymer adhesives.

Adhesives based on a mixture of a phenolic resin and polyvinyl formal or butyral were develop during the Second World War, the formal system largely in England as the method of bonding and the adhesive known as Redux, and the butyral system largely in America under three or four proprietary names.