Agricultural silica-reinforced rigid polyurethane foam for high-performance and sustainable insulation materials

The demand for sustainable materials in building construction is rising due to the increasing global energy consumption and the need for energy-efficient buildings. Rigid polyurethane foam (RPUF) is widely used as an insulating material, but its thermal performance can be further enhanced through sustainable modifications. This study explores the incorporation of silica nanofillers extracted from agricultural waste as a strategy to improve the thermal insulation and mechanical properties of RPUF. Silica was extracted from rice husk, bamboo leaf, and corn cob. Silica derived from rice husk was further incorporated into RPUF formulations as the most promising reinforcing silica source. The thermal conductivity test revealed that RPUF containing 0.25 wt% silica (FSR_0.25) exhibited the lowest thermal conductivity (0.023 W/m⋅K), representing a 9.45 % improvement over neat RPUF (FSR₀) attributed to the nucleation effect of silica incorporation. Mechanical testing showed that the reinforcement of silica also increased the compressive strength of FSR_0.25, achieving 0.26 MPa in both parallel and perpendicular directions relative to the foam rise. Scanning electron microscopy and thermogravimetric analysis further confirmed the enhanced thermal performance of FSR_0.25. These findings demonstrate that reinforcing RPUF with silica, specifically from rice husk, optimally enhances both its thermal insulation and mechanical properties, offering a sustainable approach while addressing energy efficiency and environmental concerns.