Investigation on phase transition from flow-induced oriented form II to I in isotactic polybutene-1 with in-situ microbeam X-ray diffraction technique

Publication date: Available online 19 August 2019Source: PolymerAuthor(s): Fengmei Su, Xiaokang Yang, Beibei Dong, Jingyun Zhao, Fei Lv, Youxin Ji, Chuntai Liu, Liangbin LiAbstractSpontaneously phase transition from form II to I in isotactic polybutene-1 (iPB-1) products during storage at room temperature after processing limited their application. Investigations on phase transition in iPB-1 have practical importance, especially on oriented iPB-1 as oriented form II generated during processing where intense flow field is always imposed. The effects of flow on phase transition were studied with synchrotron radiation scanning X-ray microdiffraction (SR-μSXRD) technique with beam size of 4.5 × 5.2 μm2 in the present work. Localized flow-field was imposed by pulling glass fiber through undercooled melt. Benefiting from the high resolution of SR-μSXRD technique, the formation of fibrillar and oriented form II (cIIf and cIIo) were identified. The transformation from cIIf to fibrillar form I (cIf) completed in about 40 min, while cIIo transformed into oriented form I (cIo) partially in about 186 min. Quantitative analysis on SR-μSXRD result showed that crystallographic lattice dimension of cIIf changed comparing with that of cIIo, where a and b increased while c decreased in cIIf. An obvious correlation between crystallographic lattice deformation and phase transition kinetics was is identified. Local internal stress plays an important role in promoting the phase tran...

Source: Polymer - August 20, 2019 Category: Chemistry Source Type: research