Stretchable Phase Change Composites
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Date
2019-05-07
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Johns Hopkins University
Abstract
Currently phase change materials (PCMs) are widely used to store thermal energy and control the temperature by dissipating heat. Without simply embed PCMs into construction, more researchers are focus on utilizing PCMs into clothing and electronics, since the heat dissipation is always a problem of human body and electronic devices. However, different from utilizing PCMs in construction, the applications of clothing and electronics are requiring PCMs should be stretchable so that they can fit the motion of human body and the complex shapes of electronics. But PCMs are not capable to be stretchable, thus, some stretchable matrix materials should be used to form composites with PCMs. The purpose of this essay is to fabricate stretchable phase change composites with PCMs, with the highly-stretchable material PDMS used as the matrix of composites. And the paraffin is used as PCMs in composites since paraffin is safe, cheap, have high latent of heat and proper phase change temperature range which is close to human body. Three different kinds of composites are fabricated in this essay, a) simple PDMS-based phase change composites, b) reinforced phase change composites and c) modified phase change composites. From a) to b), carbon nanotubes are added into composites to reinforce the tensile strength and thermal conductivity. Also, trying have high heat capacity for reinforce composites, the content of microcapsules is fixed at 35 wt.%. From b) to c), surface modification is applied to improve both tensile strength and thermal stability of composites. The results of thermal and mechanical characterizations of composites demonstrates that both thermal and mechanical properties are improved by reinforcement and modification. Based on the stress-strain curves, the strains of all composites are higher than 0.7 (mm/mm), which means the sample will elongate 70% of its original length and demonstrates the composites have high stretchability. With the reinforcement and modification, composites have high heat capacity, stretchability and tensile strength. This makes composites potentially useful in applications requiring materials with complex shapes and high strength such as cooling of human body and electronics.
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Keywords
Phase change materials, Stretchable composites, PDMS, Polymer, CNTs