Novel phase change materials using thermoplastic composites

In this work a Polyamide 12 (PA12) matrix was melt compounded with different amounts of discontinuous carbon fibers with different length and encapsulated paraffin, in order to develop novel thermoplastic composites with thermal energy storage/release capability. The microstructural, thermal and mechanical properties of the resulting materials were investigated. SEM images demonstrated how a rather good fiber matrix adhesion was obtained both by using long and short carbon fibers, while the microcapsules seem to be partially damaged by melt compounding operations and present also an interfacial debonding. DSC tests revealed how the melting enthalpy increased with the capsules amount, but the thermal energy storage/release capability of the composites was limited by the partial breakage of the microcapsules and the consequent molten paraffin leakage within the material. The introduction of microcapsules in the PA12 matrix determined an evident decrease of the elastic modulus, of the stress at yield and of the deformation at break, even when carbon fiber reinforcement was present, probably because of the limited interfacial adhesion between PA12 matrix and the microcapsules.