Impact of Encapsulated Phase Change Material Additives for Improved Thermal Performance of Silicone Gel Insulation

Abstract

Passive cooling through phase change materials (PCM) creates beneficial complimentary cooling techniques aimed at providing thermal gradient mitigation during device operation without additional power requirements. These have been well studied but are difficult to implement due to complications concerning effective enclosure of the liquid phase. Encapsulated PCM particles can be embedded in other materials to form composites with form stable solid–liquid phase transitions. This study characterizes a new composite of silicone gel and encapsulated phase change materials (ePCMs) for use as an encapsulant. The ePCMs contain a paraffin core and titania shell resulting in a self-contained solid–liquid phase transition producing an average of 132.9 J/g of latent heat capacity. The gel composites gain latent heat capacity as a linear function of ePCM concentration by weight. The 30% ePCM sample contains 41.0 J/g of latent heat capacity, approximately 30% of ePCM control samples. The specific heat capacity of the silicone gel without ePCMs is 1.539 J/g-° C and 2.825 J/g-° C for the ePCM particles. As the ePCM concentration increases, the specific heat capacity is increased toward the highest value of the pure ePCMs across all temperature ranges. The coefficient of thermal expansion of the composites is increased with ePCM concentration up to a maximum of 96% in the 20% ePCM concentration. The elastic modulus remains relatively constant across ePCM concentrations and temperatures. In the needle–needle breakdown voltage testing the 20% sample has a 6 kV/mm reduction in dielectric strength and higher than 20% ePCM samples show increased variability in strength due to the dispersed particles. Overall, the results from these material characterizations demonstrate the promise of dielectric composites containing ePCM particles to add passive cooling capability into electronics devices without complex structures.