In-situ synchrotron X-ray studies of crystallization of β-nucleated iPP subjected to a wide range of shear rates and shear temperatures

Abstract

Previous study focused on the shear-induced crystallization of β-nucleated iPP under fixed shear rate and temperature [1]. In this work, in-situ synchrotron X-ray was used to investigate the crystallization behavior of well-selected β-nucleated iPP under thermo-mechanical conditions in a wide range of shear rates from 2 to 50 s−1 and shear temperatures from 133 to 150 °C. At lower shear rates, we found that the overall crystallization rate of the β-nucleated iPP was reduced compared with that under quiescent condition. This is mainly ascribed to variation of nucleation-dependent process after application of shear pulse, causing strong reduction of β-nucleating efficiency. As the shear rate increases from 2 to 50 s−1, the dimensionality of crystal growth basically decreased while the long period of lamellar structure tended to slightly increase. During the shear-induced crystallization, a decreasing temperature was significantly associated with decreased overall dimensionality of crystal growth but increased crystallization rate. Finally, we observed an abnormal increase of long period with time for β-nucleated iPP sheared at 133 °C.