Degradation and stability of PA1012-based Poly(ether-block-amide) 1: The impact of multiple extrusion by the twin-screws

Abstract

The degradation and reorganization of poly(ether-block-amide) (PEBA) with polyamide1012 as hard segments and poly(tetramethylene oxide) (PTMO) as soft segments was characterized by a combination of nuclear magnetic resonance spectroscopy (NMR), differential scanning calorimetry (DSC), scanning electron microscope (SEM), small amplitude oscillatory shear (SAOS) after the PEBA was subjected to four times of extrusion cycles by the twin-screws. Chain scission resulted in a decrease of molecular weight. Consequently, the aggregate structure and morphology were also reconstructed. An increase of crystallization temperature and a decrease of the full width at half maxima of the crystallization peak were witnessed for the hard segment of PEBAs after each extrusion, especially after the first processing, which also resulted in increase of the long period. PEBAs showed a remarkable decrease of elongation at break and the tensile strength after the second extrusion, but the Young's modulus was almost kept stable.The microscopic evolution of PEBAs during unilateral and cyclic extension were further studied by in-situ wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS), which show the extent of orientation, the evolution of superstructure, the occurrence of strain-induced crystallization are almost the same across different samples, possibly due to the stretching rate was slow. The residual strain of the PEBA after four times extrusion was found higher than the rest of PEBAs, partially due to a lower extent of the microscopic orientation relaxation.