Sustainable Polymer Acoustic Composites from Waste Cotton, Coffee Husk, and Sawdust for Functional Applications

Abstract

Acoustics and thermal insulation materials are essential for improving energy efficiency and reducing environmental impact. This study explores the development of composite materials from waste cotton fiber, coffee husk, and sawdust, focusing on their thermal conductivity and sound insulation properties. Various sample compositions were prepared and tested for ceiling insulation applications, with weight ratios determined using a simplex lattice design. The results highlight the superior performance of these waste-derived composites compared to traditional insulation materials, offering a sustainable and effective alternative. The optimal composite composition, containing 33.33% cotton fiber, 33.33% coffee husk, and 33.33% sawdust, achieved the highest thermal insulation value of 0.052% and a thermal conductivity of 0.048 W/mK. Sound absorption coefficients (SAC) were measured using the impedance tube method (ASTM E1050) across frequencies from 1600 to 5000 Hz. The CFS4 composite demonstrated outstanding high-frequency sound absorption, particularly above 2500 Hz, while the increased thickness of the CFS6 composite enhanced sound absorption at medium and low frequencies. With sound absorption coefficients exceeding 82.0%, these materials exhibit exceptional acoustic properties. Moreover, thicker composites were found to improve thermal insulation significantly. These findings position the developed waste composites as a promising, eco-friendly solution for thermal and acoustic insulation in sustainable construction.