Poly(L-lactic acid) twisted nanofiber yarn prepared by carbon dioxide laser supersonic multi-drawing

摘要

Poly(L-lactic acid) (PLLA) twisted nanofiber yarn (TNFY) was continuously prepared using a CO2-laser supersonic multi-drawing apparatus equipped with a twister-winder that offers independent control of winding speed (S-w) and twisting speed (S-T). TNFYs with various twist numbers (n(T)), twist angles, and bulk densities were produced by changing S-w and S-T. TNFYs with a wide n(T) range of 395-1276 T m(-1) were obtained. Furthermore, the mechanical properties of the obtained TNFYs depended upon the degree of twist. The maximum Young's modulus was 3.06 cN dtex(-1) at S-T = 300 T min(-1) and S-w = 0.440 m min(-1), and the maximum tensile strength was 0.36 cN dtex(-1) at S-T = 365 T min(-1) and S-w = 0.440 m min(-1). The Young's modulus had a maximum value at optimum obliquity because the high twist reduced the contribution of fiber strength to the yarn hardness due to fiber obliquity in the yarn. The tensile strength increased with increasing S-T because the frictional forces among the NFs were increased by twisting at higher S-T.