Characterization and optimization of the thermal properties of silicones for their use as elastocaloric materials

Abstract

In recent years, elastocaloric (eC) materials have attracted increasing interest as an alternative to conventional solid-state cooling systems due to their ability to produce reversible thermal changes when subjected to cyclic mechanical deformations. This property makes them particularly appealing from the perspective of energy efficiency and sustainability, as they offer an alternative to conventional refrigerant gases, which are often harmful to the environment. However, the large-scale application of these materials is limited by their thermal conductivity, a clear drawback in polymers such as natural rubber (NR) or liquid silicone rubber (LSR), due to their insulating properties. The main objective of this study is to optimize the thermomechanical properties of LSR through the addition of ceramic reinforcements and control of the vulcanization process. Unlike NR, LSR does not undergo stress-induced crystallizations (SIC), but due to its flexibility and chemical resistance, it is considered a promising candidate for eC application if its conductivity can be improved. This study begins with a comparative literature review on the eC effect in elastomeric polymers and shape memory alloys, the analysis of the Mullins effect, SIC kinetics in NR, and the various reinforcements used in research to enhance the thermal conductivity of LSR. A second stage involves thermal characterization using HOTDISK and DSC techniques to evaluate thermal conductivity and heat capacity, as well as hardness test to verify the correspondence between the measured hardness and the specified by the supplier. Finally, based on the interpretation of all results, the thermal conductivity, heat capacity, and hardness of LSR were obtained, along with a theoretical study of the most promising ceramic reinforcements to implement and enhance LSR’s thermal conductivity