Nowadays, oil palm trunk (OPT) has become one of the potential alternatives as a supply for the wood-based industry due to the abundance of OPT waste in Malaysia. The poor properties of OPT contribute to the OPT plywood with low strength compared with commercial wood composite. There are many recent studies related to quality improvement using thermosetting, especially with formaldehyde-based resins such as urea formaldehyde (UF) and phenol formaldehyde (PF). However, there are very limited studies related to palm trunk plywood using thermoplastic impregnation and formaldehyde-free adhesive. Concerning to formaldehyde effects, it can be avoided by replacing with a thermoplastic adhesive, such as acrylonitrile butadiene styrene (ABS). Free soaking impregnation technique was conducted in this study because of the simple and economical process. In order to improve properties of thermoplastic palm trunk lumber, the physical properties of oil palm wood based on zoning (peripheral, central, and inner zone) were investigated. The inner zone contains a high moisture content of the OPT lumber in green condition and low in density of OPT lumber in dry condition due to the distribution of parenchyma tissue was gradually increased from the peripheral zone to the inner zone. After dried, OPT lumber at the inner zone had a cavity and mostly occurred the defects such as warping, twisting, cupping, others. Therefore, OPT lumbers from the peripheral and middle zones in this study were selected to treat with ABS resin content. A preliminary study was conducted to palm trunk lumber treated with different ABS resin content and soaking time. However, single OPT lumber treated with the different soaking time not been greatly influential to the physical and mechanical properties of thermoplastic palm trunk lumbers were observed fluctuate with increase soaking time. The variation of anatomical of OPT lumber may effect the results of the physical and mechanical properties. Thus, OPT lumbers treated within 15 minutes of soaking time seen enough to produce thermoplastic palm trunk plywood. Thermoplastic palm trunk plywood was conducted by different orientation of plies (parallel and perpendicular of OPT grain). Parallel-ply thermoplastic palm trunk plywood shows greater values of flexural and compression strength compared to commercial wood composites. While the cross-ply thermoplastic palm trunk plywood shows a lower value compared to commercial wood composites. This might be related to the different grain direction between two plies of thermoplastic palm trunk lumber caused lower bonding. In this study, 10% ABS parallel-ply thermoplastic palm trunk plywood shows the potential among 5% to 15% of ABS resin contents that affect the greater flexural strength and elasticity, and compression strength compared to commercial wood composites. ABS resin is thermoplastic polymer that allows ABS repeated melted and cooled compare to thermoset resin that cannot be recycled, reformed and cooled compare to thermoset resin that cannot be recycled, remolded upon heating. So, it can be processed in liquid state (which is during impregnation) and solid state (after drying process. Overall, the results showed that ABS resin is considered as one alternative resin to improve properties of palm trunk as well it is free formaldehyde resin.
