Halloysite-Decorated Mechanically Robust Polyurethane Nanocomposite Foams for Acoustic Relevance

Noise pollution affects human health and the environment. In this study, halloysite nanoclay (HNC) was employed as a bio-nanofiller with different ratios (1–5 wt %) to improve the thermal, mechanical, and sound absorption capabilities of the flexible polyurethane (FPU) foam. FPU/HNC composites were characterized using X-ray diffraction, Fourier transform infrared, and field emission scanning electron microscopy techniques. In addition, porosity, apparent density, and sol fraction for FPU/HNC composites were investigated. Compared with the unfilled FPU foam, the results of the FPU/HNC 1% sample showed that the density achieved a maximum value of 38.17 Kg/m3, while the porosity was reduced to 83.48%. Moreover, the sol fraction reached the highest value of 13.4% for the FPU/HNC 5% sample. Furthermore, thermogravimetric analysis revealed that adding 1 wt % HNC improved thermal stability than the unfilled FPU. Nevertheless, the DSC measurement proved that HNC increased the glass transition temperature (Tg) for the composites' soft segments. Intriguingly, the mechanical measurements exposed that the compressive and tensile strength of the FPU/HNC 1% sample was enhanced to 158.93 and 154.45%; at the same time, the elongation at break dropped to 124.04%. Nevertheless, the sound absorption measurements (20 mm thickness) showed a slight shift to the mid-frequency range (315–1600 Hz) for FPU/HNC composites than the unfilled FPU.