The effect of alkaline treatment and mixture of HDPE-PP matrixes on the red meranti wood-plastic composites

The purpose of this study was to analyze the effect of alkaline treatment of red meranti sawdust and the composition of a mixture of high-density polyethylene (HDPE) and polypropylene (PP) plastics on the physical and mechanical properties of wood-plastic composites (WPC) products. Alkaline treatment was done by soaking sawdust in a 3% NaOH solution for 2 hours. The HDPE-PP blend as a polymer matrix has been adjusted at 100:0, 75:25, 50:50, 25:75, and 0:100 (w/w). The ratio of sawdust and plastic was 40:60 (w/w). Maleic Anhydride with a concentration of 3% was used as a coupling agent. The panels were processed by pressing (30 bar) at a temperature of 180 °C for 20 minutes to give a panel density of 0.7 g/cm3. The determination of the physical and mechanical properties of WPC was carried out according to ASTM standards. A factorial design with five replications was used for each parameter. The results showed the ranges of panel density (0.63–0.73 g/cm3), moisture content (2.82–3.58%), water absorption (13.58%-30.50%), thickness swelling (1.30–4.51%), MoE (2,229.67–3,332.91 N/mm2), MoR (4.93–10.94 N/mm2), IBS (0.39–0.54 N/mm2), and impact resistance (46.63–65.72 Joule/m). The statistical analysis showed that the wood alkaline treatment caused a significant effect on all the physical properties of the WPC, as well as IBS. The different HDPE-PP ratio strongly contributed to a significant impact on the density, water absorption, and MoR. The significant effect was also found in terms of their thickness swelling and MoE after applying combination of those treatments. Furthermore, we found that the best treatment was observed from a 100% HDPE concentration due to its appropriate mechanical performance.