Development of Wood-Based Materials Bonded with Citric Acid

The development of biobased adhesives without harmful chemical agents is very important for the future. In this study, citric acid was used as a wood adhesive. Citric acid (2-hydroxy-1,2,3-propanetricarboxylic acid) is a very safe substance, and it is commercially produced by the fermentation of glucose or glucose- and sucrose-containing materials. This article shows the bonding properties of citric acid in wood-based moldings and particleboards. In wood-based molding, wood and bark powders were used as elements. Citric acid powder was mixed with wood or bark powders, and the mixture was hot pressed at 200 degrees C for 10 minutes. The wood-based moldings had good mechanical properties and excellent water resistance. When wood powder was used as an element, the specific modulus of rupture and modulus of elasticity values were 38.1 kN.m/kg and 4.9 MN.m/kg, respectively. In the case of particleboard, sucrose was used in addition to citric acid; both were dissolved in a water solution and used as an adhesive. Particleboard was manufactured at 200 degrees C for 10 minutes. The board had good mechanical properties and water resistance. When bonded with a 25/75 ratio of citric acid and sucrose, the mechanical properties of the board were comparable to the 18 type JIS A 5908 standard. We conclude that citric acid could be used as a bioadhesive for wood.