Preparation of wood adhesives based on tannins and glycerol esters (triacetate)

Abstract

The use of products obtained from gluing of wood can, directly, contributes to the conservation of forest resources, from the point of view of its full use. However, the synthetic resins used in the bonding are obtained by petroleum derivatives, whose price has grown steadily in recent years as a result of the reduction of fossil resources. An alternative would be the use of compounds derived from renewable sources, such as tannins, instead of phenol. Furthermore, driven by energy policies that encourage the use of renewable sources, we are in the midst of a biodiesel production surge. One of the co-products of biodiesel production is glycerin, which corresponding itself to 10% of the total mass of the obtained oil. Glycerin, or more specifically the glycerol, may be converted to glycerol triacetate. Thus, the objective herein was to prepare environmentally friendly adhesives, using glycerol triacetate and tannins. For preparation of the wood adhesives, glycerol triacetate and H2SO4 were mixed at 80°C for one hour. After this procedure, the tannin was added and the material subjected to the curing process. Adhesives A and B were produced with 25 and 40% tannin, respectively. The analysis of the adhesives differed only in solids content and viscosity. The shear strength and rupture percentage values indicate that the prepared adhesives have great potential and can be used commercially in the future.