Glutaraldehyde-modified starch as the binder for environmentally friendly plywood

Abstract

A standard resin system used in wood-based panel preparation was formaldehyde-based glue, which was believed to have fatal effects on the environment and human health due to the release of free formaldehyde. Therefore, the study's objective was to evaluate the physical and mechanical properties of experimental plywood made using glutardialdehyde-modified starch as environmentally friendly binder. Two gelatinisation methods were used: sodium hydroxide (NaOH) and hot water. Plywood was manufactured using starch modified with 10%, 20% and 30% glutardialdehyde. The physical testing found density value was around 0.34 g/cm3 to 0.38 g/cm3, moisture content was 19.34% to 23.67%, water absorption was between 24.56% to 71.60%, and thickness swelling between 1.18% to 7.27%. Plywood made using NaOH-gelatinized glutardialdehyde-modified starch binder has higher density and lower moisture content which are advantages for this composite type. In mechanical testing, it has been found that plywood made using NaOH-gelatinized glutardialdehyde modified starch binder has higher overall strength than plywood using hot water-gelatinised glutardialdehyde modified starch binder, measured by their bending strength and tensile shear strength. The MOR was found between 124.88 N/mm2 to 179.32 N/mm2, MOE between 8027.50 N/mm2 to 10603.90 N/mm2, and tensile shear strength between 651.64 N/mm2 to 1385.16 N/mm2. The highest glutardialdehyde: starch ratio, which is 30% of glutardialdehyde used based on the weight of starch, showed better overall plywood physical and mechanical properties. The results showed that glutardialdehyde-modified starch could be used as an alternative binder in plywood manufacturing.