Upcycling of PET plastics into diethyl terephthalate for applications as phase change materials in energy harvesting

Polyethylene terephthalate (PET) is an indispensable material in our everyday lives and upcycling of its waste has become a major area of research. Herein, the upcycling of PET waste into phase change materials (PCM) for thermal energy storage applications is presented. Hydrolysed and esterified PET waste affords diethyl terephthalate (DET), which when blended with UV-curing acrylic matrix, trimethylolpropane ethoxy triacrylate (TMPEOTA), forms a composite PCM. Chemical characterisation such as IR and NMR were conducted to confirm the presence of functional groups in the composites. The thermal properties of the composites, such as melting point and thermal degradation were obtained and DET exhibited a relatively high melting enthalpy of 94.1 J/g at about 39.9 degrees C. The form stability and thermal performance was studied for composites made of different DET loading weight percentages from 50 to 90 %. A loading rate of 80 % (D80) was found to provide best latent heat capacity while maintaining its form stability and minimizing leakage. Finally, to assess the performance of D80 as a thermal storage material, a thermal response test was performed and D80 was able to prevent significant rise in temperature for about 60s during its phase transition as opposed to TMPEOTA control.