A study of the relationship between the tensile strength and dynamics of as-spun and drawn poly(glycolic acid) fibers

Abstract

Higher-order structure of as-spun and highly-drawn poly(glycolic acid)(PGA) fibers has been characterized by solid-echo 1H NMR and WAXD methods. In the observed WAXD patterns, as-spun PGA fiber shows a very broad amorphous peak and highly-drawn PGA fibers show very sharp diffraction peaks at 2θ = 21.9° from which the crystallinities of highly-drawn fibers with the drawing ratio(λd.r.) of 2.5, 2.8 and 3.2 are determined to be 0.50, 0.51 and 0.52, respectively. These show that the crystallinities of the PGA fibers with different drawing ratios are very close to each other. On the other hand, the observed solid-echo 1H NMR free induction decay(FID) signals of as-spun and drawn PGA fibers show a multi-component decay consisting of the short T2 component and the long T2 component. From these results, the short T2 component was assigned to the crystalline region and the immobile amorphous region, and the long T2 component was assigned to the mobile amorphous region. It was found that the fractions of the short T2 component and the long T2 component of highly-drawn fibers largely depend on the drawing ratio λd.r. and temperature, and that the fractions of the short T2 component for drawn PGA fibers with λd.r. of 2.5 at 120°C and 160°C are 0.85 and 0.56, respectively. Further, it was found that the fractions of the short T2 component for the drawn fibers above 160°C are very close to the crystallinities determined by the WAXD patterns, but the fractions of the short T2 component at 120°C are different from each other. The structural characterization was made to understand mechanical property of the drawn PGA fibers. Then, it was found that the fraction of the corresponding amorphous region is closely related to the ratio of the tensile strength after hydrolytic acceleration test to that before hydrolytic acceleration for PGA fibers. © 2008 The Society of Polymer Science.