Investigation of eco-friendly plywood bonded with citric acid - starch based adhesive

Concerning the environmental issues, the eco-friendly panel product has been developed by using natural based adhesive to ensure safe product application for human health. In this study, Paraserienthes falcataria veneer and citric acid - starch were used in the manufacturing of plywood. The 30 wt% concentration of citric acid - starch-based adhesive was prepared and it was spread to each veneer with 150 g/m(2) of glue spread. The plywood was constructed by 3 layers of veneers. The dimension of each veneer was 30 x 30 x 0.2 (cm). The effect of composition ratio between citric acid (CA) and starch (St) as natural sources of adhesive on delamination and shear strength of the plywood was investigated. The plywood was produced under pressing conditions of 180 degrees C for 10 min with 5 MPa of pressure. The variation of compositions ratio (CA:St) were 90:10, 80:20, 70:30, 60:40, 50:50. The research results showed that the plywood with 50 wt% additional of starch had the lowest delamination and highest shear strength. The shear strength of plywood satisfied Standard National Indonesia (SNI) of plywood for general use. Infrared (IR) spectral analysis demonstrated the presence of ester linkage, indicating that the carboxyl groups of citric acid reacted with the hydroxyl groups of the wood veneer. Therefore, 50:50 of composition ration between CA and St was effective composition ratio in the manufacturing of eco-friendly plywood.