First-Order Phase Transition in a Nylon 66 Crystal

抄録

Electron diffraction patterns and specific heat at constant pressure (C_p) are recorded in a temperature range between approximately 300 K and 500 K for a nylon 66 crystal precipitated at 418 K from 0.05-wt% 1,4-butanediol solution. The C_p is found to take a maximum value at 468 K (T_t) under 0.1 MPa (atmospheric pressure). Three reflections of 100, 010 and 110 can be observed independently in an electron diffraction pattern, all of which show symmetrical single-peak profiles at temperatures lower than T_t, while 010 and 110 profiles are found to be asymmetric or to have shoulders in the smaller-diffraction-angle region at T_t. These results give the first evidence that two crystalline phases coexist or that first-order phase transition occurs at T_t in the nylon 66 crystal.