Thermal and acoustic insulation properties of wood plastic composites (WPCs) for interior housing applications

The thermal and acoustic insulation properties of low-cost wood plastic composites (WPCs) made from waste biomass of Acacia saligna and recycled low-density polyethylene (rLDPE) were studied. The WPCs were processed at three different blending ratios (50, 60, 70 wt% of wood), with two wood particle sizes (0.3 and 0.5 mm), at different hot press times (10 and 30 min) and temperatures (150 and 180 °C) to obtain boards with optimum mechanical, physical, thermal, and acoustic insulation properties for application in social housing in South Africa. A heat flow meter (HFM) apparatus and an acoustic impedance tube were designed and built to measure the thermal conductivity (k-value) and sound transmission loss (STL) properties of the WPCs. Boards from larger sized particles had lower conductivity values. The boards that were pressed at 70 wt% biomass ratio and at the lower press temperature and time had the lowest heat conductivity value (0.044 W/m‧K) which can be attributed to higher incidence of lattice defects and vacancies due to a higher proportion of thermally modified biomass. The boards pressed at 50 wt% biomass at 150 °C for 10 min possessed a higher mass/stiffness ratio which resulted in improved STL via reflection and absorption of acoustic energy in the mid-frequencies (500–2000) Hz. Boards produced with 60 wt% biomass exhibited the best noise attenuation level (8–14 dB) and thermal conductivity (0.048–0.056 W/m‧k), making them the most suited for use as insulation boards to improve living conditions in social houses in South Africa.