Blends of polyamide 12 and maleic anhydride grafted paraffin wax as potential phase change materials

Polyamide 12 (PA12) was blended with a high content of a maleic anhydride functionalized paraffin wax in an attempt to prepare shape stabilized phase change materials for energy storage. The morphology of the immiscible blends, and possible interactions between the blend components, were characterized through scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR) analyses. Although it could not be conclusively established, the obtained results indicated a strong possibility of hydrogen bonding interaction between the anhydride -CO groups on the wax and the -N-H groups in the amide. Such an interaction was clearly evident in the thermal, thermo-mechanical, and mechanical behaviour of the blends, as investigated through differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), stress relaxation measurements, and thermogravimetric analysis (TGA).