Adhesion Theories in Wood Adhesive Bonding

Investigating the theories or mechanisms responsible for wood adhesive bonding has been an important aspect of wood science and technology research over the past century. Understanding the nature of adhesion in wood and wood-based composites is of importance because of the fact that wood is adhesively bonded in over 80 percent of its applications. For wood bonding, studying adhesion theories requires an understanding of wood material characteristics, surface science, polymer characteristics, and the interactions between polymers and surfaces. Th state-of-the-art categorizes adhesion theories or mechanisms into seven models or areas. Thse are: mechanical interlocking; electronic or electrostatic theory; adsorption (thermodynamic) or wetting theory; diffsion theory; chemical (covalent) bonding theory; acid-base theory; and theory of weak boundary layers. Th goal of this paper is to provide a concise, critical, state-of-the-art review on adhesion theories in wood adhesive bonding with an emphasis on factors inflencing bond creation in woodbased material applications. Over 200 papers were reviewed and information is presented with recommendations for future studies on wood adhesion.