Shape-stable phenolic/polyethylene glycol phase change material: kinetics study and improvements in thermal properties of nanocomposites

Abstract

Storage, transformation, and absorption of energy play effective roles in application and performance of heat and thermal energy beneficiary. Phase change materials (PCMs) are substances with high heat of fusion which can be utilized to design thermal protective and thermal energy storage systems. However, PCM leakage in phase changing process is a well-known disadvantage of the PCM containing systems. One of the approaches to avoid PCM leakage is to prepare shape-stabilized PCM in polymeric composites. In this study, polyethylene glycol (PEG), as a PCM, was shape-stabilized with low leakage in the novolac colloidal structure with no solvent and through a sol–gel in situ polymerization process. Supercooling is a negative associate phenomenon in these systems, which may occur due to the low rate of nucleation and nucleation growth. Nanoclay was used to avoid supercooling of PEG. PEG supercooling significantly decreased when 2.5 wt% of nanoclay was incorporated. This is due to the role of nanoclay particles as the crystal nuclei. The sol–gel polymerization kinetics of novolac resin in the presence of nanoclay and molten PEG was also studied using the Kamal–Sourour model. Results showed that 85 wt% of PEG was preserved with leakage less than 3.5 wt% by shape stabilization encapsulated with colloidal structure of the phenolic resin. Nanoclay improved the thermal properties of the system and reduced the supercooling about 20%. Moreover, based on Kamal–Sourour model, polymerization kinetics could suggest a lower novolac curing rate in the presence of molten PEG and nanoclay.