Effect of Rice Husk Powder on the Composition and Characteristics of Rigid Polyurethane Foam Based on Cardanol Resin

The growing demand for a greener environment has led to an increased interest in sustainable and eco-friendly materials, processes, and products. This trend has prompted researchers in the polyurethane (PU) industry to explore bio-based materials for manufacturing composite products with improved properties and applications. Recent findings discovered an inexpensive, biodegradable, and abundantly available agricultural by-product obtained from cashew nutshell liquid called cardanol. It has enormous potential as a raw material for preparing resins for different industrial applications. Therefore, this work aims to study the possibility of preparing polyurethane foam (PUF) composites from cardanol-based polyol. In this study, a novel polyol resin was prepared by reaction of glutaraldehyde with cardanol, and its structure was verified by Fourier transform infrared spectral analysis. Then, the PUF biocomposites were prepared via the reaction of cardanol polyol with 1,6-hexamethylene diisocyanate in the presence of rice husk (RH) as a reinforcing biobased filler at different concentrations (5-30 wt%). The mechanical properties, density, and water absorption of the green viscoelastic PUF/RH composites were investigated. The results revealed that the addition of RH fibers to the prepared PUF improved significantly the compressive strength and water absorption resistance of the prepared bio composites. Moreover, the result of this research is considered an added value in exploiting agricultural waste (cardanol and RH fibers) as renewable and sustainable resources of raw materials in various industries and environmental protection.