The effect of hydrogen-bond (H-bond) organization, evaluated by the crystal perfection index (CPI), on the Brill transition of long-chain polyamide 1012 upon heating was investigated with variable-temperature wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and Fourier transform infrared spectroscopy (FTIR). A sufficiently high cooling rate was required to prepare samples with randomly distributed H-bonds (i.e., a low CPI) because this inhibits the reorganization of the 2-D hydrogen sheet structure during cooling from melts. The Brill temperature (T B) values of the T210 and T270 samples, which were prepared by cooling from 210 and 270 °C at a rate ranging from 5 to 100 °C/min, were determined. The T B values of the T270 samples determined by WAXD and FTIR show a significant linear decrease with the decreasing CPI, whereas that of the T210 samples remains constant because its CPI is independent of the applied cooling rate. Both the T210 and the T270 samples quenched by a liquid nitrogen bath are γ-phase at ambient temperature, suggesting that the critical cooling rate required to reduce the CPI depends on the content of hydrogen-bonded H-bonds at each temperature for the melts. The T B gap between the T210 and T270 samples with a similar lamellar thickness is caused by the content of randomly distributed H-bonds.

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