Synthesis, characterization and properties of palmitic acid/high density polyethylene/graphene nanoplatelets composites as form-stable phase change materials

In this work, form-stable phase change materials (FSPCM) consisting of palmitic acid (PA) and high density polyethylene (HDPE) were modified by graphene nanoplatelets (GNP). In the FSPCM, PA was used as a solid–liquid phase change material (PCM) for thermal energy storage, HDPE was a supporting material to prevent the leakage of the melted PA, and GNP were added for improving thermal conductivity and shape stabilized of the FSPCM. Thermal properties and shape stability of the composites vary with their different mixture ratios. According to the results of Fourier transformation infrared spectroscope (FT-IR) and X-ray diffractometer (XRD), the composites have advantages like stabilized chemical structure and crystalline phase. The differential scanning calorimeter (DSC) results show that the FSPCM has a constant melting temperature of around 62°C and a high latent heat of at least 155.8J/g. With the help of scanning electronic microscope (SEM), a layer structure and uniform dispersion of the PA is observed in the modified FSPCM. The thermos-gravimetric analyzer (TGA) and thermal cycling test results indicate that the modified FSPCM has a good thermal reliability, and the leakage of the PA drops significantly with the assistance of the GNP. The thermal conductivity of the FSPCM was measured by thermal conductivity meter and it increased to 0.8219W(mK)^‑1 which is nearly 2.5 times as high as that of the pure FSPCM, when the mass fraction of the GNP is 4%. It is anticipated that the modified FSPCM possess a potential application in solar energy and building heating systems.