Structure and characterization of nylon 46

Solid-state NMR and TEM measurements were carried out in order to investigate the crystallization behavior of nylon 46 from the perspective of its molecular structure and dynamics. The characteristic chemical shift difference between the crystalline and amorphous phases is observed for the methylene directly connected to nitrogen. This chemical shift difference indicates the existence of the gauche-conformation around the βB–βB bond in the amorphous phase. As the crystallization proceeds, the crystalline phase increases by the conformational change in the amorphous phase. The molecular motion in the crystalline phase is fixed during the initial stage of the crystallization, while that in the amorphous phase is in the mobile state until the crystallization is almost finished. By using the 13C T1 difference, the spectra for the crystalline and amorphous phases are separately obtained. From the TEM observations, the lamellar thickness was constant during the crystallization. On the other hand, the thickness of the crystalline and amorphous phases increases and decreases, respectively, with the crystallization. The model for the nylon 46 crystallization mechanism is proposed.