Fabrication of ZnATH-(O) NPs -Integrated microencapsulated phase change materials (MEPCMs) for improved heat storage capacity

• Phytofabricated zinc oxide nanoparticles were prepared using anthocyanin (ATH) extracted from red cabbage. • ZnATH-(O) NPs (1–7 wt%) were incorporated into the PCM matrix and microencapsulated via mini-emulsion polymerization. • At 7 wt% ZnATH-(O), microcapsules showed the highest encapsulation ratio (77.9%) and efficiency (77.8%). • ZnATH-(O) incorporation enhanced latent heat capacity, thermal stability, and heat transfer efficiency. • Optimized ZnATH-(O)- modified PCM microcapsules demonstrated superior thermal energy storage performance. A novel microencapsulated phase change materials (MEPCM) was synthesized via mini-emulsion polymerization technique by introducing zinc oxide (ZnO) nanoparticles (NPs) into the PCM matrix, and encapsulated within the polymer shell of poly(styrene-co-butylacrylate) (PS-co-PBA) crosslinked with Divinylbenzene. The nano ZnO dopant utilizes anthocyanin (ATH) extract derived from red cabbage that acts as reducing, capping and stabilizing agent which optimizes the thermal behavior and stability of the prepared MEPCM. A series of MEPCMs were prepared by mixing different weight percentage (wt%) of NPs. The thermal behavior, stability, reliability, microstructure and chemical composition of the resultant MEPCMs were investigated by Differential Scanning Calorimetry (DSC), Thermogravimetry Analysis (TGA), Infrared Thermography (IFT), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and Powder X-ray Diffraction (PXRD) respectively. From the DSC result, it was observed that the optimal microcapsule performance was achieved at a 1:1 core-to-shell ratio, with ZnATH-(O) NPs doped at 7 wt%, resulting in a maximum encapsulation ratio of 77.9% and an encapsulation efficiency of 77.8%. TGA analysis revealed that all the MEPCMs demonstrated two step deterioration and exhibited good thermal stability. FE-SEM images confirmed that the produced microcapsules exhibited spherical shape with a smooth surface, but as the wt% of NPs increases, agglomeration appears. The results highlighted that ZnATH-(O) NPs integrated MEPCMs have substantial potential as thermal energy storage materials for moderate-temperature applications within the temperature range of 30-40°C.