Flexible composite phase change material with improved hydrophobicity and thermal conductivity characters for thermal management

Phase change materials (PCMs) are increasingly popularized in the field of passive thermal management. However, several inherent defects such as strong rigidity, weak hydrophobicity and poor thermal conductivity have seriously hindered their widespread development. This work introduces a novel composite PCM with thermally-induced flexibility as well as enhanced hydrophobic and thermally conductive abilities, which is synthetized by physical melting and mixing of palmitic acid (PA), olefin block copolymer (OBC) and hexagonal boron nitride (h-BN). Experimental results demonstrate that OBC helps to realize flexibility and hydrophobicity, while h-BN is essential to spurring thermal conductivity growth but incapable of impairing surface wettability. 66.5 wt% PA, 28.5 wt% OBC and 5 wt% h-BN are convinced to be the appropriate formula of composite for the hydrophobic modification and the weighing between thermal conductivity and thermal storage capacity. The as-prepared flexible PCM reverses its surface wettability from hydrophilicity to hydrophobicity, accompanied by 27.0 % increment in water contact angle compared with the case of using only PA. The resultant also presents fine physiochemical compatibility, suitable phase transition parameters, and excellent thermal stability and reliability. Furthermore, highly reliable hydrophobicity is confirmed under four harsh conditions for prolonged application.