In-situ structure development during processing of poly(trimethylene terephthalate) and poly(vinylidene fluoride) fibers studied by synchrotron x-ray scattering.

摘要

It is the intention of this investigation to understand the mechanism of microstructure development in polymer fibers under mechanical and thermal processing. In a polymer system, the mechanism of microstructure development is usually closely related to the crystal phase behavior of the polymer. Therefore, monomorphic poly(trimethylene terephthalate) (PTT) and polymorphic poly(vinylidene fluoride) (PVDF) are chosen as the subject of this research. Besides, PTT is a polyester newly commercialized by the Shell Chemical Company, and is just now entering the textile and thermoplastic application field. However, very little about the structure development of PTT is known.; Small-scale spinning and drawing apparatuses were utilized to perform in-situ small- and wide-angle x-ray scattering (SAXS, WAXS) on PTT fibers during spinning and continuous drawing. Measurements on PTT and PVDF fibers under hot/cold stretching were also performed.; In-situ and ex-situ WAXS experiments from PTT suggest the development of an oriented amorphous phase during spinning when take-up speed is below 3000 m/min. The relative amount of this phase depends on the take-up speed.; Transformation of crystalline chain conformation from equilibrium tggt to tttt can be observed as suggested by the unit cell c-dimension calculation. While the c-dimension of the unit cell increases during drawing, a concomitant decrease in crystallinity and increase in a- and b-dimension are observed. A defect creation/transport model is proposed to account for these experimental results.; The cold/hot stretching of PTT suggested that unit cell dimensions, crystallinity and orientation of drawn PTT fibers are dependent on temperature and strain.; Cold stretching of PVDF fibers prepared between 10.6–61.0 m/min suggests that fibers yield at an early stage of deformation, resulting in alternating necked and un-necked regions along the fiber. Results from SAXS and WAXS analysis suggest that the formation of defects during yielding and plastic flow facilitates the α to β crystal phase transformation.; Besides experimental work, advanced computational algorithms are adopted to facilitate the analysis of two-dimensional (2-D) WAXS patterns.; This work has made advances in understanding the combined thermal and mechanical effects on structure development of polymer fibers during processing. (Abstract shortened by UMI.)