The Use of Sodium Hydroxide Hydrolysis to Study the Fine Structure of Undrawn and Drawn High-Speed Spun Polyethylene Terephthalate) Fibers

Abstract

Abstract The fine structures of undrawn and drawn high-speed spun poly-(ethylene terephthalate) (PET) fibers, 0.86 dL/g intrinsic viscosity, formed at speeds from 1615 to 3329 m/min, were investigated. Increasing the spinning speed and drawing resulted in greater levels of orientation and crystallinity in the untreated fibers. The relatively high molecular weight of the PET yielded undrawn products of higher orientation and crystallinity than those obtained by workers using PET of lower molecular weight but spun at similar speeds. A linear relationship between cohesive and optical anisotropy was found for the undrawn and drawn fibers. Aqueous sodium hydroxide hydrolysis was utilized to reveal the presence of any radial variations in structure. In the undrawn fibers, hydrolysis revealed that a more oriented layer was present very near the fiber periphery at higher spinning speeds. In the drawn samples a small but significant progressive decrease in birefringence was generally observed as the center of the fiber was approached. The drawing process appears to produce fibers without a skin-core structure and less susceptible to tenacity loss due to surface defects.