Influence of different hot-pressing conditions on the performance of eco-friendly jabon plywood bonded with citric acid adhesive

The citric acid (CA)-based adhesive, as a new environment-friendly adhesive, has been developed and used for the manufacturing of plywood to resolve the problem of formaldehyde-based adhesive for human health. The effects of pressing time and temperature on physical and mechanical properties of plywood were examined. Three-layer plywood panels were bonded using CA adhesive with a 134 g/m2 of single glue spread on White jabon wood veneer. The plywood panels were hot-pressed at 5 MPa with three different pressing temperatures, 180°C, 190°C, 200°C, for 10 min, and also different pressing times, 4, 7, 10 min at 190°C. The physical and mechanical properties, such as moisture content, delamination, and shear strength, were evaluated according to JAS 233:2003. The results show that the plywood with pressing temperature of 190°C for 10 min had lower delamination and greater tensile shear strength than those of other plywood panels. Moreover, some properties of the plywood fulfilled the requirement of JAS 233:2003. Based on the FTIR analysis, citric acid plays an important role in the formation of ester linkages (R-COO-R) via esterification between carboxyl groups of citric acid and hydroxyl groups of White jabon wood veneer, resulting excellent properties of plywood.