Waste-derived PVC leather and footwear composite panels: fabrication and characterization for building insulation

Growing industrial waste from artificial leather production and footwear produced caused serious disposal problems in India. At the same time, buildings in hot climates needed insulation materials that would help reduce the cooling energy requirements, while being cost effective and eco-friendly. In this paper, a sustainable insulation panel was prepared with waste artificial leather scrap, footwear scrap, and crumb rubber as the main raw materials. The goal was to develop an insulation material that would be inexpensive and high performing, as an alternative to commercial products such as polyurethane foam. Fifteen different compositions for inner core were fabricated and glued with a PU/MDI resin. Glass Fiber Reinforced Gypsum (GFRG) sheets were used as the outer layers of the sandwich panel. All samples were tested for density, compressive strength, thermal conductivity, internal bonding and noise absorption. Multi-criteria decision making of the TOPSIS method was used to prioritize the samples according to the performances. Microstructural inspection was consistent with the performance data. Of all the formulations, the LSIP-15 sample (100 percent artificial leather scrap, 30 percent footwear rubber and 10 percent crumb rubber) worked the best. It exhibited density of 0.746 (g/$${cm}^{3}$$), compressive strength of 6.23 (mega Pascal) and 0.695 (internal bonding) and noise reduction coefficient of 0.32. Its thermal conductivity was up to 0.052 W/mK, which was 31% less than typical commercial PU foam panels (0.076 W/mK) and over three times less than traditional GFRG walls. A theoretical analysis using FEA to evaluate its heat resistance confirmed that the thermal resistance of a three-layer GFRG-LSIP-15-GFRG panel was far better than that of a normal wall system. The results confirmed foam as air voids reduced heat transfer and leather fibers increased mechanical strength, and crumb rubber enhanced acoustic damping. The present research showed a new way of using industrial wastes in energy efficient building applications. The proposed panel provided lower thermal conductivity, similar strength and sound insulation to many commercial materials, while relieving the burden on landfills and reducing the number of raw materials. The work had great potential for low-cost insulation in educational and residential buildings, particularly for developing regions where a circular economy approach to construction is coming. The proposed panels were made using waste artificial leather, footwear scraps, and crumb rubber collected from Indian SMEs. The best sample (LSIP-15) had good strength, low heat transfer, and reduced noise. The three-layer insulation panel stopped more than three times the heat compared to a normal wall. The panels worked like PU foam but were cheaper and more eco-friendly for buildings.