Using silicagel industrial wastes to synthesize polyethylene glycol/silica-hydroxyl form-stable phase change materials for thermal energy storage applications

Abstract

Polyethylene glycol form-stable phase change materials (PEG FSPCMs) have received much attention in recent years for thermal energy storage applications due to their remarkable thermal properties. However, the conventional synthesis of PEG FSPCMs usually employed chemical grade regents as starting materials, which is unlikely suitable for large-scale industrial preparation of PCMs. In the present work, silicagel industrial wastes were employed as starting materials for the first time to synthesize a polyethylene glycol/silica-hydroxyl compound (PEG/SHC) form-stable phase change material using a facile sol-gel method. The morphology and chemical compatibility were characterized using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The thermal energy storage performance was evaluated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermal constants analysis, respectively. The results indicated that the PEG was encapsulated in the SHC matrix through a physical interaction, and the weight fraction of PEG in the FSPCM could be as high as 80% with no significant leaking liquid observed. The thermal energy storage capacity in this FSPCM was found to be (59.38–132.4) J/g and (63.56–133.4) J/g in the melting and crystallization process, respectively, as the loaded PEG weight fraction ranging from 50% to 80%. The thermal conductivity of the FSPCM enhanced by the SHC matrix was determined to be as high as 30% compared with that of the pure PEG. Additionally, the FSPCM synthesized in this method could maintain a stable thermal property during the heating/cooling cycles. On the basis of these results, it was demonstrated that the sol-gel method developed in this work could not only obtain PEG based FSPCMs with good performance for thermal energy storage, but also propose an effective way of producing economic benefits by reusing silicagel industrial wastes.