Preparation, characterization and crystalline transition behaviors of polyamide 4 14

A new polyamide, nylon 4 14, was synthesized and characterized in this paper. The polymer was prepared by melt polycondensation, which yielded materials of molecular weight about 15,000 g/mol. The product was characterized by means of elementary analysis, intrinsic viscosity, infrared spectrometry, 1H and 13C nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. In addition, the crystalline transition behavior of nylon 4 14 was carefully investigated by variable-temperature X-ray diffraction (XRD). It was found that well-melt-crystallized nylon 4 14 undergoes Brill transition at 170°C on heating. When it crystallized at high temperature from the melt, nylon 4 14 crystallized directly into a kind of α phase with two peaks in its XRD patterns, which is very different from nylon 6 6 and nylon 10 12 and similar to nylon 10 10. Upon further cooling to room temperature, nylon 4 14 preserved the triclinic structure (α phase).