Effect of SiO₂ Particles on the Crystallization and Formation of Hydrogen Bonding in Biobased Polyamide 56

As PA56 cannot have 100% intermolecular hydrogen bonds (HBs) regardless of how the molecular chains are arranged, the crystallization properties of PA56 are not as good as those of petroleum-based nylon. To replace petroleum-based nylon and broaden the applications, it is necessary to improve the crystallization properties of PA56 and elaborate the relationship between crystallization and hydrogen bonding. In this work, nano-SiO2 with different particle sizes was chosen as the nucleation agent of biobased PA56, and the isothermal and nonisothermal crystallization of PA56 were investigated by differential scanning calorimetry (DSC). It was shown that SiO2 can significantly improve the crystallization properties of PA56 composites, especially for SiO2 with a smaller size. Furthermore, the influence of SiO2 on the formation of hydrogen bonds during the crystallization process was also studied by in situ Fourier transform infrared (FTIR) spectroscopy. The addition of SiO2 into PA56 plays a role in the increase of the conversion of the free carbonyl group to the hydrogen-bonded carbonyl group, which accelerates the formation of intermolecular HBs. The increase of HBs may be the factor for the improvement of the crystallization rate.