Exploring the polymorphic behavior of a β‐nucleated propylene‐ethylene random copolymer under shear flow. Issue 2 (19th February 2020) - Zhang, Chunbo
Abstract: Shear flow strongly affects the polymorphism and crystallization kinetics of semi‐crystalline polymers. In the present work, the crystallization behavior of a β ‐nucleated propylene‐ethylene (P‐E) random copolymer was studied both under quiescent and shear flow by using in‐situ wide‐angle X‐ray diffraction. It was observed that shear flow could shorten the induction time, fasten the crystallization rate and increase the degree of crystallinity. The populations of different crystal modifications varied significantly upon shearing. Especially the β crystals fraction decreased with shear strain. When the shear strain was higher than 100 with a fixed shear rate of 5 s −1, the β crystals almost disappeared. Meanwhile, both the fractions and the crystallization rates of α and γ crystals were enhanced by shear flow. The complicated polymorphic behavior can be interpreted by the nucleation kinetics. Abstract : The polymorphic behavior of a β ‐nucleated propylene‐ethylene random copolymer under shear is studied using in situ X‐ray diffraction. Shear flow influences significantly on the crystal modifications: β crystals are greatly suppressed and the crystallization rate and population of α/γ crystals are enhanced by shear. Although both the β ‐nucleating agent and shear flow reduce the nucleation barrier of the β crystals, the combination of the two factors is detrimental for the β crystal formation.