butyral

Butyral, in a polymer context, most commonly refers to polyvinyl butyral (PVB), a resin formed by acetalizing polyvinyl alcohol with butyraldehyde. PVB is widely used as an interlayer resin in laminated safety glass, where it bonds glass surfaces and helps absorb impact while maintaining clarity.

Production of PVB involves several steps. Polyvinyl acetate is first hydrolyzed to polyvinyl alcohol, and then partially reacted with butyraldehyde in the presence of an acid catalyst to form acetal linkages along the polymer chain. The resulting material is a flexible thermoplastic that is typically formulated with plasticizers to tailor properties such as toughness, softness, and peel strength for specific applications.

Key properties of butyral resins include high optical clarity, good adhesion to glass, and the ability to absorb and dissipate energy during impact. The performance of PVB films can be adjusted with plasticizers and process conditions, producing sheets or films that are cast or extruded for lamination. PVB remains transparent over a range of temperatures and provides some acoustic damping, which is advantageous in glazing applications.

Primary applications are laminated safety glass for automobile windshields and architectural glazing, where the interlayer helps hold glass fragments together when broken and reduces injury risk. Additional uses include decorative laminates and certain specialty coatings and adhesive systems where a transparent, tough interlayer is desired.

The term butyral derives from butyraldehyde, the aldehyde used to form the acetal linkage in polyvinyl butyral. It is part of the polyvinyl acetal family of polymers.