In-situ synchrotron X-ray investigating crystallization of isotactic polypropylene with /3-nucleating agent during injection molding

The coupling effects of mold temperature and packing pressure fields on structure evolution of isotactic polypropylene with /3-nucleating agent (iPP//3) /3 ) during injection molding were systematically investigated using high- throughput in-situ synchrotron X-ray diffraction/scattering technology for the first time. A small number of /3-crystals are generated in pure iPP and iPP//3 /3 due to the shear flow introduced by the filling stage. The formation of /3-crystals induced by /3-nucleating agent (/3 /3-NA) in iPP//3 /3 commenced after about 1.8 s of melt filling. The two- stage growth of /3-crystals in iPP//3 /3 exhibits differences in growth time and orientation. Both the decrease in the lattice spacing and the /3-a- a transition in iPP//3 /3 occur at the packing stage and are suppressed at high mold temperatures (>= 90 degrees C). The polymorphism competitive growth of iPP//3 /3 is revealed, and the effects of coupling external fields on it are well elucidated by combining finite element simulation and classical nucleation theory. Additionally, the scattering intensity and orientation of iPP//3 /3 lamellae initially increase to a maximum value and subsequently decrease until reaching the equilibrium with time. Our current work lays a solid foundation to precisely customize the crystal structure of iPP//3 /3 in practical processing and thus to produce high-performance iPP products.