The properties of the adhesive's primary component determine the effectiveness of the bond. The superior characteristics of resorcinol resin adhesives-such as high bond strength, water resistance, and durability against aging-are inherent to the resorcinol resin itself. Conversely, soy protein adhesives lack high strength and water resistance but are odorless; these are intrinsic traits of soy protein. The proportions of the various components in an adhesive must be balanced correctly. If the resin content is too low, bond strength suffers; however, an adhesive consisting entirely of resin without fillers is neither economical nor necessarily the strongest.
To achieve a strong bond, an adhesive must be capable of wetting and diffusing into the wood; however, excessive wettability causes the adhesive to soak deeply into the wood, resulting in a starved bond line and high adhesive consumption. Wettability is closely linked to viscosity: higher viscosity results in poorer wettability. Since both strong acids and strong alkalis damage wood, the adhesive must maintain an appropriate pH level. Adhesives with an excessively short pot life are prone to gelling or pre-curing, leading to poor bonding, whereas curing speeds that are too slow result in wasted time. Furthermore, curing conditions and the degree of cure directly impact the quality of the bond.
