Adhesives in the Wood Industry

Abstract

Adhesive bonding is the key factor in how to utilize wood material for the production of increased-value wood products. Manufacturing wood-based composites depends on forming high-performance bonds between wood adherends. The quality of wood bonding—and hence the properties of wood-based panels—are determined to a great extent by the type and performance of the adhesive. The evidence for a high capability toward innovation in the wood-based panels and the adhesive industry is shown by the considerable diversity of types of adhesives used for the production of wood-based panels. Further on, adhesive bonding of wood continues to be one of the most challenging areas of research in wood science, due to the highly variable and complex nature of wood as a raw material. Wood adhesives technology, hence, is an advanced science merging adhesive preparation and formulation with a variety of application technologies. As in all applications of adhesives, cohesion and adhesion are the main features to be followed, in combination with proper application technology and press conditions, irrespective of the applied temperature. Though extensive information is available on adhesives and adhesion, basic research on the adhesion behavior of wood, including the evaluation of the formed microstructure of the bondline as the main performance parameter within the produced bonded products, still needs to be promoted. This is to be seen as a fundamental approach as well as an application to industrial bonding processes in a great variety of modes, from laminated wood preparation in the carpenter’s shop to industrial production of wood-based panels of several thousand cubic meters per day. Aspects such as surface properties of wood related to bondability, adhesive characteristics concerning wetting and penetration, formation of the interphase of wood and adhesive, interfacial reactions between the wood surface and the adhesive, chemical curing or physical solidification of the adhesive, behavior of the adhesive in the formed bondline, and the microstructure and properties of the bondline as the basis for the performance of wood-based composites are the main features of bonding.