Shearing is unavoidable during the polymer process, and isotactic polypropylene (iPP) is one of the most used commercial polymers. iPP mixed with beta-nucleating agent TMB-5 was isothermally crystallized at 135 degrees C from melts under various shear conditions and investigated via synchrotron radiation small-angle and wide-angle X-ray scattering (SAXS and WAXS) techniques with CCD detector. The shear-induced crystalline structure and the orientation of the samples were studied according to the obtained WAXS and SAXS patterns. The results showed that both the crystallinity of alpha-iPP and beta-iPP are in direct proportion to the orientation degree rather than shear rate especially at high shear rate, which proves that wall slip should not be neglected when taking shear effect or rheological behavior into consideration.
Industrial and Engineering Chemistry Research, 2014, Vol 53, Issue 34, p. 13513-13521