Preparation of poly(lactic acid) fiber by dry‐jet‐wet‐spinning. I. Influence of draw ratio on fiber properties

Poly(lactic acid) fiber was prepared by dry‐jet‐wet spinning of the polymer from chloroform solution and with methanol as the precipitating medium. The as‐spun fiber was subsequently made into high strength fiber by two‐step process of drawing at a temperature of 90°C and subsequent heat setting in the temperature range of 120°C. The draw ratio had significant influence on the crystallinity and the tensile strength of the fiber. The fiber with the tenacity of 0.6 GPa and modulus of 8.2 GPa was achieved at a draw ratio of 8. The differential scanning calorimetry revealed an increase in the glass‐transition temperature with the increase in the draw ratio, which suggests the orientation of chains during the drawing process. The surface morphology of the filament as revealed by scanning electron microscopy shows that fibers are porous in nature, but a significant reduction in the porosity and pore size of the fiber was observed with the increase in the draw ratio. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1239–1246, 2006