Poly(l-lactic acid) nanofiber multifilament prepared by carbon dioxide laser supersonic multi-drawing

- Nanofiber multifilament (NFMF) made by CO2 laser supersonic multi-drawing (CLSMD).
- Continuous PLLA-NFMF can be prepared by CLSMD.
- PLLA-NFMF obtained was composed of approximately 85,000 NFs with an average diameter of 0.311 μm.
- NFMF braid could be prepared with a braiding machine.
- CLSMD is a green process for the preparation of NFMF composed of various polymers without the use of a solvent.

Poly(l-lactic acid) (PLLA) nanofiber multifilament (NFMF) was continuously prepared by CO2-laser supersonic multi-drawing (CLSMD), which was conducted by laser irradiation of the PLLA fibers in a supersonic jet. The CLSMD apparatus used for the continuous preparation of NFMF consists of a fiber supply spool, a continuous-wave CO2 laser, a vacuum chamber with ZnSe windows, a fiber injection orifice plate, a net conveyor, an interlacer, and a take-up roll. NFs collected onto the net conveyor were intermingled by the interlacer and then wound by the take-up roll. PLLA-NFMF obtained at a laser power of 40 W and a chamber pressure of 30 kPa was composed of approximately 85,000 NFs with an average diameter of 0.311 μm. The obtained NFMF was annealed at 85 °C under an applied tension of 5.14 MPa to improve the mechanical properties; the annealed NFMF had a Young's modulus of 2.1 GPa and a tensile strength of 68 MPa. NFMF braid could be prepared with a braiding machine because the mechanical properties were improved by annealing. CLSMD is a new route for the preparation of NFMF composed of various polymers without the use of a solvent.