Abstract
Leaching and instability in wax-based phase change materials (PCMs) are serious application problems. Herein, we developed paper-like (~ 100 µm) flexible, composite PCMs by hydraulic compression of 1-cm-thick polyimide foams between an aluminum foil and a (nano) ceramic composite Parafilm®. An unfilled PCM film placed between the foam and the aluminum surface ensured strong adhesion between the collapsed foam and the metal. Different concentrations of nano-BN and micro-SiC particles were compounded into Parafilm® in order to optimize the thermal performance. Based on infrared imaging, the monoliths containing 30 wt% micro-SiC outperformed all other systems including BN/SiC hybrids. The next best thermal performance was observed with the 60 wt% nano-BN composite. Due to compression, the cellular structure of the polyimide foams collapsed irreversibly while being impregnated by the PCMs from both sides. High-k fillers improved impregnation into the collapsed foam and enabled excellent shape stability and leakage prevention.Graphical abstract
Highlights
Polyimide (PI) foams were first produced and commercialized by EIDuPont de Nemours (Dupont) company in the 1960s [1, 2]
Before constructing the sandwich structures, we investigated the changes in the cellular microstructure of the PI foam before and after compression
The first one is an initial phase of linear elasticity with a very low modulus that seems to extend beyond 20% strain, and a quasi-plateau region up to about 60% where the foam is able to resist the applied compressive load
Summary
Polyimide (PI) foams were first produced and commercialized by EIDuPont de Nemours (Dupont) company in the 1960s [1, 2]. Polymer composites containing electro-conducive fillers such as nanocarbon materials and BN have been shown to be the next-generation materials for electromagnetic interference shielding and electronics, as mentioned earlier [40,41,42,43,44] Both BN and SiC are high thermal conductivity ceramics with attractive semiconducting properties. The cellular structures of the PI foam collapsed irreversibly resulting in a thinner central layer This simple and solvent-free process can be used to form stable and lightweight PCM layers or coatings on metallic surfaces and the produced layered composites can be integrated into many different thermal energy storage technologies including large area applications such as energy saving buildings
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