Wood-plastic composites as insulative panel from waste expanded polystyrene: Optimizing thermal conductivity and mechanical behaviour

The primary aim of this research is to upcycle waste EPS into functional wood-plastic composites (WPCs) for building insulation applications. Post-consumer EPS was dissolved in equal proportion of mixed solvent of acetone and ethyl acetate and reinforcing it with bamboo pulp fibre mixture. Composite panels with varying EPS content (40-70 wt%) and fiber -pulp ration (30:70 and 40:60) were fabricated using compression molding. Additionally, foaming agent sodium bicarbonate was added in concentration of 2.5 %, 5% and 7.5% in 60% EPS composite to evaluate the pore size effect on thermal and mechanical properties. Thermal load modelling for a single room was also performed to analyze the required energy consumption. Mechanical testing revealed that the sample containing 60 wt% EPS exhibited a better flexural strength of 22 MPa, and compressive strength of 24.68 MPa, and thermal conductivity of 0.216 W/m-K. WPCs with 60% EPS with 2.5% pore foaming agent showed controlled pore formation, resulting in the lowest thermal conductivity of 0.116 W/m-K, which is 7.2% less than that of without foaming agent. The 60% EPS formulation with controlled porosity has emerged as a balanced solution, offering adequate mechanical integrity while significantly lowering the thermal conductivity. This study suggests that utilizing EPS to fabricate WPCs can simultaneously address two critical sustainability challenges: diverting EPS waste from landfills, and reducing building energy demands through reduced thermal conductivity.