CAS Key Laboratory of Engineering Plastics,Beijing National Laboratory for Molecular Sciences,CAS Research/Education Center for Excellence in Molecular Sciences,Institute of Chemistry,Chinese Academy of SciencesUniversity of Chinese Academy of SciencesD
Ping Zhu;Chenxu Zhou;Xia Dong;Bryan B.Sauer;Dujin Wang
Poly(ether-ester)(PEE) multi-segmented copolymers films were characterized by a combination of in situ wide-angle X-ray diffraction(WAXD) and small-angle X-ray scattering(SAXS) during cyclic deformations. PEE had crystalline hard segments of poly(butylene terephthalate)(PBT) with poly(tetramethylene oxide)(PTMO) soft segments. Reversible strain-induced crystallization(SIC) of PTMO was evaluated by WAXD and Fourier transform infrared spectroscopy(FTIR) during loading and unloading. The phase transition of the PBT hard phase was not detected by WAXD or FTIR upon stretching. Further analysis of 2 D SAXS showed progressive orientation of PBT ribbon-like lamellae at lower stresses, followed by formation of oriented nano-fibrils at higher stresses. Only when the sample was unloaded at very low stresses was the long period in the strain direction mostly reversible. For relaxing from medium and high stresses, tilting of PBT lamellae domains was found in the relaxed states. Under certain higher loading stresses, SAXS scattering in the strain direction is due to correlations between hard and soft blocks along the length of well oriented "load bearing" nano-fibrils which also comprise PTMO SIC which was quantified by WAXD and FTIR. The film results were contrasted with those for high speed melt-spun PEE fibers.
ELASTOMER DURING CYCLIC DEFORMATION BY IN-SITU WAXD/SAXS;PBT;AN INVESTIGATION OF THE MICROSTRUCTURAL EVOLUTION OF THERMOPLASTIC POLY;ETHER-ESTER