An experimental study on castor oil-based flexible PU foam coated with silica hydrogel for acoustic and fire resistance applications

This research explores the production of flexible polyurethane foam using castor oil with varying densities, treated via dip coating with sodium silicate and hydrochloric acid to form a protective silica hydrogel. This treatment enhances the foam’s acoustic and fire resistance properties. The sound absorption coefficient (SAC) is measured using an impedance tube per ASTM E 1050-12, and the noise reduction coefficient (NRC) is calculated. Specimen S5 shows superior performance with an NRC of 0.336 for coated and 0.283 for non-coated conditions, a significant 19% improvement. TGA revealed that non-coated foam showed initial sublimation at 240 °C and substantial degradation with a 75% weight loss at 400 °C, while coated samples like S5 began to decay at 300 °C, showing only a 25% weight reduction at 400 °C. These results highlight the influence of foam density on acoustic enhancement, making the foam ideal for automotive interiors by providing a quieter and safer environment for passengers.