Form-stable polyethylene glycol distearate–rice husk silica composite phase change material for effective latent heat thermal energy storage

Polyethylene glycol distearates (PEG-DS), synthesized via a modified Fischer esterification method using azeotropic distillation, were investigated as novel form-stable phase change materials (FSPCMs). PEGs of three molecular weights (1500, 4000, and 6000) were reacted with stearic acid in toluene under reflux to remove water at the azeotropic point, forming ester bonds confirmed by FTIR and 1 H/ 13 C NMR analyses. The resulting PEG-DS samples (PS1500, PS4000, PS6000) exhibited fusion latent heats of 100.6, 153.5, and 161.6 J /g and melting points of 39, 53, and 59 °C, respectively, with some deviation from pristine PEGs. To stabilize the PCMs and prevent leakage, silica powder were extracted from rice husk via acid leaching and controlled combustion, yielding particles sized 20–100 μm, with 97 wt% purity and 282 m 2 /g surface area. These were integrated with PEG-DS via melt infiltration (80 wt% PEG-DS, 20 wt% silica), forming composites labeled RHS/PS1500, RHS/PS4000, and RHS/PS6000. DSC results showed that while the composites experienced ∼20% latent heat reduction, they maintained acceptable energy storage capacity and eliminated leakage during thermal cycling. Supercooling effects were significantly reduced due to silica's nucleating properties. These results demonstrate that PEG-DS synthesized through azeotropic distillation is an effective PCM with adjustable melting points and robust thermal properties. When supported by bio-derived silica from rice husk, the FSPCMs offer enhanced stability and sustainability for thermal energy storage applications. • Synthesized polyethylene glycol distearates (PEG-DS) via azeotropic distillation as novel PCM, • Tuned melting points and latent heats by selecting PEGs with different molecular weights, • Extracted high-purity, high-surface-area silica from rice husk as a sustainable supporting material, • Achieved leakage-free composites with reduced supercooling and stable thermal performance.