Polymer, Vol.53, No.16, 3540-3547, 2012
Simultaneous SAXS/WAXS experiments on shear induced iPP crystallization near nominal melting temperature
Simultaneous small- and wide-angle synchrotron radiation X-ray scattering was performed to monitor the evolution of crystalline structure within the iPP melt during and after applying pulse shear. The iPP melt was subjected to a strong pulse shear of 240 s(-1) for 6 s at temperatures between 150 and 170 degrees C below and above the nominal melting temperature T-m It was found that the imposed shear affected the melt only at lowest temperature. Structures generated during flow above 150 degrees C were too dilute to be detected. To extract the hidden structure, the melt was cooled to crystallization temperature of 150 degrees C either immediately after shearing or after annealing at shear temperature for up to 30 min. This treatment manifested with an anisotropic structure in a few minutes after quenching, undetectable when both shear and annealing temperatures presented the same value. The data obtained revealed also close correlations between annealing time, shear temperature and incubation time. (C) 2012 Elsevier Ltd. All rights reserved.