Journal
JOURNAL OF APPLIED POLYMER SCIENCE
Volume 81, Issue 1, Pages 251-260Publisher
JOHN WILEY & SONS INC
DOI: 10.1002/app.1436
Keywords
poly(L-lactic acid); biodegradable fibers; melt spinning; viscosity-average molecular weight; tensile properties
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Biodegradable poly(L-lactic acid) (PLLA) fibers were processed by a two-step melt-spinning method (melt extrusion and hot draw) from PLLA with three different viscosity-average molecular weights (494,600, 304,700. and 262,800). Before spinning, the polymer flakes were first milled into powders and dried under vacuum. Viscosity-average molecular weight of PLLA following the fabrication process was monitored. Tensile properties of as-spun and hot-drawn fibers were investigated. Morphology of the PLLA fibers was viewed under a scanning electron microscope. Crystallinity of these fibers was assessed by thermogram analysis of differential scanning calorimetry. Results showed that the extent of decrease in the viscosity-average molecular weight of PLLA dropped sharply by 13.1-19.5% during pulverization and by 39.0-69.0% during melt-extrusion. The hot-draw process in this study had a little effect on the viscosity-average molecular weight of PLLA. Smoother fibers could be obtained for the die temperature at least 230 degreesC for raw materials with higher crystallinity (more than 75%) and at least 220 degreesC for raw materials with lower crystallinity (about 60%). The as-spun fibers showed crystallinity of 16.5-22.8% and the value increased to 50.3-63.7% after hot draw. Tensile moduli of the as-spun fibers were in the range of 1.2-2.4 GPa, which were raised to 3.6-5.4 GPa after hot draw. The final PLLA fibers with 110-160 mum diameters showed tensile strengths of 300-600 MPa. (C) 2001 John T;Wiley & Sons, Inc.
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