Structural Evolution of LLDPE-LMW/HMW Blend during Uniaxial Deformation as Revealed by In Situ Synchrotron Radiation X-ray Scattering

摘要

The structural evolutions of LLDPE-LMW/HMW blend during uniaxial deformation at temperatures of 80 and 120 ℃ were investigated by the in situ synchrotron radiation small-and wide-angle X-ray scattering(SR-SAXS/WAXS). The magic sandwich echo(MSE) sequence was used to detect a virtually dead-time-free induction decay(FID) for solid-state NMR analysis. The thermal property of the blend was first checked by DSC,and the temperature dependence of the overall crystallinity was obtained by MSE-FID. The onset melting temperature is determined to be 116 ℃(DSC), and the enhanced π-flip motions in the crystalline domains are clearly observed at T>60 ℃ by MSE-FID. For deformation at 80 ℃, the lamellae become staggered in the strain-softening region as shown by the four-point SAXS pattern, whereas further deformation leads to the melting-recrystallization in the strain-hardening region. For deformation at 120 ℃, the six-point SR-SAXS signal appears just after the four-point SR-SAXS signal, which indicates the formation of new lamellae along deformation direction. In addition, no phase transition occurs in the whole deformation process at both temperatures. Current work shows the detailed temperature dependence microstructural evolution of LLDPELMW/HMW blend. This is expected to provide more structural information for correlating microscopic structure with macroscopic mechanical performance.