Influences of gamma irradiation on structure, thermal stability and thermal energy storage properties of form stable phase change materials

Form stable phase change materials (PCMs) were prepared from high density polyethylene (HDPE), poly(ethylene-co-vinyl acetate) (EVA), organophilic montmorillonite (OMT) and paraffin. The influences of gamma irradiation on the structure, thermal stability and thermal energy storage properties of form stable PCMs were studied by X-ray diffraction (XRD), scanning electronic microscopy (SEM), thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC). The XRD results indicated that the morphological structure of intercalation for form stable PCMs would not be appreciably varied by gamma irradiation. The SEM images showed that the intermolecular cross-linking induced by gamma irradiation made the three-dimensional network structure more compact and the interface more illegible. The results of TGA analyses indicated that the thermal stability of form stable PCMs after gamma irradiation was higher than that of the corresponding PCMs before gamma irradiation, and the enhancement slightly decreased for form stable PCMs with the increase in OMT amount as compared to the HDPE-EVA/paraffin blend, indicating that the nanodispersion of OMT resulted in superior irradiation resistant properties. The DSC results showed that the formation of intermolecular cross-linking led to increases in the transition temperature T-t and the melting temperature T-m and a decrease in latent heat for form stable PCMs.