Multifunctional glass fiber/polyamide composites with thermal energy storage/release capability

Thermoplastic composite laminates with thermal energy storage (TES) capability were prepared by combining a glass fabric, a polyamide 12 (PA12) matrix and two different phase change materials (PCMs), i.e. a paraffinic wax microencapsulatedin melamine-formaldehyde shells and a paraffin shape stabilized with carbon nanotubes. The melt flow index ofthe PA12/PCM blends decreased with the PCM concentration, especially in the systems with shape stabilized wax. Differentialscanning calorimetry showed that, for the matrices with microcapsules, the values of enthalpy were approximately the 70% of the theoretical values, which was attributed to the fracture of some microcapsules. Nevertheless, most of the energystorage capability was preserved. On the other hand, much lower relative enthalpy values were measured on the compositeswith shape stabilized wax, due to a considerable paraffin leakage or degradation. The subsequent characterization ofthe glass fabric laminates highlighted that the fiber and void volume fractions were comparable for all the laminates exceptfor that with the higher amount of shape stabilized wax, where the high viscosity of the matrix led to a low fiber volumefraction and higher void content. The mechanical properties of the laminates were only slightly impaired by PCM addition,while a more sensible drop of the elastic modulus, of the stress at break and of the interlaminar shear strength could be observedin the shape stabilized wax systems.