Experimental investigation of enhanced form-stable phase change material based on stearic acid/expanded graphite/SEBS composite

Phase change materials (PCMs) are the materials that can absorb and release energy during their phase transition. The materials have become ubiquitous but still face challenges. The inevitable transition from solid phase to liquid phase in these materials during operation limits their utility in application areas that require leak-proof properties like orthopaedic mattresses or gel packs, or applications requiring self-load-bearing capabilities (such as ceiling tiles and building walls). Entrapment of PCM in porous matrices is one of the promising methods of capturing the PCM and limiting the flow of materials in the liquid phase. The present study discusses the preparation of exfoliated graphite from commercially available intercalated graphite. The process of exfoliating the intercalated graphite has been holistically characterized using x-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The graphite with a surface area of 47.37 cc/g with a purity of 99% was found to have a maximum absorption of 80% (w/w) stearic acid as PCM. In addition, this paper investigates two synthetic routes to prepare the shape-stabilized PCM. The blends are characterized and compared along six indicators: transition point, latent heat capacity, thermal conductivity, exudation behavior, FTIR, and SEM. Composite 1 refers to stearic acid absorbed in the exfoliated graphite. Composite 2 refers to the stearic acid absorbed in exfoliated graphite which is further treated with an elastomer SEBS. The leak test performed on both blends signifies that SEBS is an essential ingredient. The PCM composition optimized in this study can unlock various thermal applications with critical requirements where direct exposure of chemicals to the user is unacceptable. Further, the study itself is envisaged to serve as a framework to develop enhanced shape-stabilized PCMs with tuneable thermal conductivity and extended operation life in application areas where leakage in liquid phase is a concern.