Synthesis, Characterization and Water Absorption Analysis of Highly Hygroscopic Bio-based Co-polyamides 56/66.

This study aims to develop highly hygroscopic bio-based co-polyamides (CPs) by melt co-polycondensation of polyamide (PA) 56 salt and PA66 salt with varying molar fractions. The functional groups and the chemical structure of the prepared samples were determined by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The relative viscosity was determined with an Ubbelohde viscometer. The melting behavior and the thermal stability of CPs were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Furthermore, the water absorption behavior of CP hot-pressed film was studied. The results reveal that the melting point, the crystallization temperature and the crystallinity of CPs firstly decrease and then increase with the molar fraction of PA66 in CPs. The copolymerization of PA56 with PA66 leads to an obvious increase in water absorption. The CPs with PA66 molar fraction of 50% possess a high saturated water absorption rate of 17.6%, compared to 11.6% for pure PA56 and 7. 8% for pure PA66. [ABSTRACT FROM AUTHOR]