Utilization of devulcanized waste rubber tire in development of heat insulation composite

This study aims to investigate the possibility of recycling devulcanized rubber tires for their use as fillers for thermoplastic thermal insulators. A devulcanized rubber tire was ground into powder and then mixed with polystyrene in different proportions (0–50 wt%) using a melt extruder. The mixture was then transferred to a hot press for fabricating the final sample. The effect of devulcanized rubber tire content on the physical, thermal, and mechanical properties of devulcanized rubber tire–polystyrene composites was investigated. Thermal conductivity measurements were verified using series and parallel conduction models and the Hashin and Shtrikman model. Composites with less than 40 wt% devulcanized rubber tire content exhibited superior properties, with thermal conductivity ranging from 0.0502 to 0.07084 W/(m⋅K), density from 462.8 to 482.32 kg/m³, compressive strength from 11.66 to 7.47 MPa, and flexural strength from 40.4 to 19.26 MPa. Moreover, alkaline treatment of the devulcanized rubber tire further improved the mechanical properties and thermal stability of the composite. The results are supported by characterization techniques such as scanning electron microscopy, thermogravimetric analysis, and Fourier-transform infrared spectroscopy. The chemical treatment was found to enhance the coherence between treated devulcanized rubber tire and polystyrene. The novel devulcanized rubber tire–polystyrene composite can be used as an alternative insulation material because of its superior properties compared with those of conventional insulation materials. Furthermore, the environmental and economic implications of using devulcanized rubber tire–polystyrene composites as a new insulation material are discussed herein.