Flow-induced polymer crystallization was seldom carried out under pressure because there is higher requirements for the experimental device than under pressure. However

not only flow field

but pressure is involved in real processing. So

authors'group performed studies on flow-induced crystallization of polymer under pressure using homemade device and found the flow-induced crystallization behaviors of polymers under pressure are notably different from those under normal pressure. For isotactic polypropylene (iPP)

unique oriented sphere-shaped crystals could be formed under pressure and flow. In a short time (30min)

the lamellae of iPP could quickly thicken and generated thick lamellae with a high melting temperature close to the equilibrium melting point (ca. 180℃). The reason is that the activity energy for lamellar thickening remarkably decreased under pressure and shear. Meanwhile

we also obtained the window to generate a large amount of β-iPP for the system of iPP mixed with β nucleating agent. For polylactic (PLA)

the similar lamellae thickening phenomenon was also observed under flow and pressure. In addition

we obtained β-PLA directly from PLA melt under pressure and flow. These research results provide theoretic and experimental data for tailoring the morphology and structure of polymers in practical processing.