Upcycled textile and agricultural waste for thermal and acoustic insulation solutions

This study investigates a novel combination of materials, incorporating pantyhose and rice husk, to develop sustainable insulation panel candidates, an approach that has not been previously explored in the literature. Pantyhose, composed primarily of polyamide and elastane, are frequently discarded due to their short lifespan, while rice husks are a common agricultural by-product. Pantyhose waste was processed into fibers and formed into web structures using a carding machine. Two production methods were employed to create insulation panels: needle punching and hot pressing. For needle-punched panels, the fiber composition and number of layers (2-plied and 4-plied) were varied. Composite panels were produced in the same plies via hot pressing, incorporating polypropylene fibers as binders (10% wt.) and rice husks in powder or granule form (20% wt.). Key performance tests included sound absorption, thermal conductivity, air permeability, fiber composition, thickness, and density. Results showed that composite panels exhibited superior sound absorption, with the addition of rice husk powder further enhancing performance; the best-performing sample (C-4P-PW) reached a sound absorption coefficient of 0.74 at 2500 Hz. Conversely, needle-punched panels provided better thermal insulation, with sample N-2P-FB achieving the lowest thermal conductivity of 0.038 W m⁻¹ K⁻¹ due to its porous structure. This study highlights the potential of combining textile and agricultural waste to develop eco-friendly insulation materials, which are considered promising candidate materials pending further validation for building applications.