Thermal Properties of α- and γ-Forms of Nylon 6

Multiple melting behavior in nylon 6 is analyzed by means of a high temperature X-ray camera (HTXC) and a differential scanning calorimeter (DSC). Melting in the intermediate phase between crystalline and amorphous ones is supposed to contribute to the higher temperature peak in DSC. The recrystallization process is confirmed for the α-form specimen. On the basis of the two-phase model, the following thermodynamical quantities are self-consistently determined for the α- and γ-forms respectively; heat of fusion, 41 and 33 cal/g, surface free energy, 57 and 47 erg/cm2 and equilibrium melting temperature, 272 and 272°C. The α-form is found to be more stable than the γ-form in the whole region below the melting temperature.