Fabrication of a form-stable phase change material with green fatty acid and recycled silica nanoparticles from spent lead-acid battery separators with enhanced thermal conductivity

Massive amounts of spent lead-acid battery separators with 50 wt % silica nanoparticles (SiNPs) can be recycled for further use. One compelling application is form-stable phase change materials (FSPCMs). This study proposes a novel tertiary eutectic mixture of green and non-toxic lauric acid, palmitic acid, and paraffin, and recycled SiNPs to find a sustainable approach to deal with industrial wastes and energy consumption. Fatty acids and paraffin are promising for thermal energy storage in buildings. However, they lack sufficient thermal conductivity, mechanical strength, and suffer from leakage. To give mechanical strength, high-density polyethylene (HDPE) was added and sintered. Microstructural analysis showed that PCM could fill scaffold voids up to 75 wt % without leaking. Thermal analyses showed a low phase change point of 33.1 degrees C and a high heat capacity of 53.9-104.4 J/g, suitable for building applications. Thermal conductivity increased by 300 %, thanks to PbO inclusion of recycled SiNPs.