Adhesives

Abstract

The American Society for Testing and Materials (ASTM) defines an adhesive as a substance capable of holding mate­ rials together by surface attachment (1). The mechanisms by which a liquid adhesive makes intimate contact with a surface, undergoing physical and chemical changes to bond surfaces together, is highly complex and understood only in part. Nonetheless, adhesives appropriately selected for compatability with adherend and service conditions can be used to great advantage in building construction. Adhesives increase strength and stiffness of building com­ ponents, uniformly transfer and distribute stresses, and combine dissimilar materials that could not be joined oth­ erwise. Applications in building construction vary widely in structural capabilities, from huge glued-laminated beams that support roof loads to nonstructural applica­ tions where adhesives support only wall coverings and decorative trim. Within the last 45 years, age-old animal and vegetable adhesives have essentially been replaced by chemically synthesized adhesives that enable the user to bond practically all materials from microchips to jet aircraft. The construction industry is the largest user of adhesives, but by far the largest proportion is used to manufacture building materials such as plywood, particle board, gypsum board, hard board, doors, sandwich panels, glass-fiber insulation, and various factory-laminated prod­ ucts. The amount of adhesive used in the construction industry to assemble building materials at construction sites and in small shops is unknown, but it is this latter group of adhesives and their applications that this article addresses. Mechanisms of adhesive bonding and the na­ tures of bonding surfaces and polymers that are common to most adhesive applications are also discussed.