Acoustic, Thermal, Mechanical, and Fire Behavior of Multifunctional Rock Wool–Leather Waste Composites for Interior Building Systems Publisher



Alizadeh F ; Sheikhmozafari MJ ; Soltani P ; Samaei SE ; Mirzaei R ; Taban E
Source: Journal of Building Engineering Published:2026

Abstract

This study investigates the development of multifunctional insulation panels based on rock wool (RW), recycled leather waste (LW), and their 50:50 hybrid composite (RW–LW) for interior building applications. A total of 24 panel configurations were fabricated by varying material composition, thickness (20–50 mm), and bulk density (300–400 kg/m3). All specimens were initially screened in terms of normal-incidence sound absorption and thermal conductivity, after which the best-performing panel from each material category was selected for further moisture absorption, flammability, and flexural characterization. In addition, the acoustic response of the selected optimized panels was analyzed using the Delany–Bazley (DB) and Johnson–Champoux–Allard (JCA) models. The results showed that both material composition and physical configuration strongly influenced performance. Among the investigated formulations, the RW–LW hybrid panel with a thickness of 30 mm and a bulk density of 400 kg/m3 exhibited the most balanced overall behavior, achieving a Noise Reduction Coefficient (NRC) of 0.64, a Sound Absorption Average (SAA) of 0.63, and a thermal conductivity of 0.061 W/m·K. FESEM observations indicated that the hybrid structure combined the finer mineral-fiber framework of RW with the rougher and more heterogeneous morphology of LW, which contributed to enhanced acoustic dissipation, particularly in the mid-frequency range. Across the analyzed frequency range below 3000 Hz, the JCA model provided closer agreement with the measured absorption spectra than the DB model, indicating that a more physically detailed framework is better suited to these heterogeneous fibrous composites. Thermal results showed that pure RW panels provided the lowest effective thermal conductivity, pure LW panels the highest, and hybrid panels an intermediate response. The selected optimized panels also satisfied the IEC 60695-11-10 HB criterion under the adopted small-scale test conditions, with flame resistance following the order RW > RW–LW > LW. Flexural testing showed that the hybrid panel exhibited the highest bending strength (1.8 MPa), followed by LW (1.6 MPa) and RW (1.3 MPa). However, the high-water uptake observed under full-immersion conditions indicates that practical use would require appropriate moisture-control measures for interior applications. Overall, the results demonstrate that hybridization of rock wool with recycled leather waste can produce an eco-efficient insulation panel with a favorable combination of acoustic performance, thermal insulation, mechanical integrity, and material-level flame resistance, while simultaneously valorizing two industrial waste streams. © 2026 Elsevier Ltd