Stretch-Induced Reverse Brill Transition In Polyamide 46

Structural transitions of polyamide 46 (PA46) films during the tensile stretch at temperatures from 37 to 249 degrees C were studied using in situ synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) and Fourier transform infrared (FTIR) techniques. The structural evolution during the stretch at different temperatures can be roughly divided into three regions. In region I (37 <= T < 180 degrees C), stretch enlarges the d-spacing gap between the (100) and (010/110) planes of a phase (triclinic), which is opposite to that during heating. In region II (180 <= T < 230 degrees C), stretch induces a reverse Brill transition, which is characterized by the single diffraction of gamma phase (pseudohexagonal) splitting into two diffractions of a phase, while further increasing the strain drives the two split diffractions to transform to a single broad diffraction. As in situ FTIR measurements reveal the continuously increasing content of trans conformation, we speculate that stretch may induce a new form, which is an intermediate structure close to both alpha and gamma phases (named alpha' phase) at large strain. In region III (230 <= T < 249 degrees C), the y phase may skip the a phase and directly transform into the a' phase. The nonequilibrium crystal phase diagrams of PA46 were constructed in the strain-temperature space and true stress-temperature space. Current results demonstrate that stretch plays a countereffect of heating on the Brill transition of PA46.