Zone‐drawing and zone‐annealing of poly(L‐lactic acid) microfiber prepared by CO₂ laser‐thinning method

Abstract

A zone-drawing and zone-annealing method was applied to the poly(l-lactic acid) (PLLA) microfiber obtained by using a carbon dioxide (CO 2 ) laser-thinning to develop its mechanical properties. The microfiber used for the zone-drawing and zone-annealing was prepared by winding at 800 m min Ϫ1 the microfiber that was obtained by irradiating the laser at 8.0 W cm Ϫ2 to an as-spun fiber supplied at a speed of 0.5 m min Ϫ1 and had a diameter of 1.5 m and a birefringence of 20.3 ϫ 10 Ϫ3 . The zone-drawing was carried out at a drawing temperature of 85°C under an applied tension of 150 MPa, and the zone-annealing at an annealing temperature of 110°C under 181 MPa. The zonedrawing and the zone-annealing were carried out at a treating speed of 0.1 m min Ϫ1 . The diameter of microfiber decreased, and its birefringence increased stepwise with processing. The zone-annealed microfiber finally obtained had a diameter of 1.2 m, a birefringence of 43.3 ϫ 10 Ϫ3 , a tensile modulus of 14.0 GPa, and a tensile strength of 1.5 GPa. The wide-angle X-ray diffraction pattern of the zone-annealed microfiber showed the existence of the highly oriented crystallites.

Poly(ethylene‐2,6‐naphthalate) nanofiber prepared by carbon dioxide laser supersonic drawing

“…A carbon dioxide (CO 2 ) laser‐thinning method developed by us could easily produce microfibers by irradiating a continuous‐wave CO 2 laser to fibers, such as poly(ethylene terephthalate) (PET),16 nylon 6,17 nylon 66,18 i‐polypropylene,19 poly( L ‐lactic acid) (PLLA),20, 21 and poly(ethylene ‐2,6‐ naphthalate) (PEN)22 fibers without highly skilled techniques. The microfiber obtained by winding on a spool in the winding speed range of 100–2500 m min −1 was monofilament microfiber with a uniform diameter.…”

Melt spinning of continuous fibers by cold air attenuation I: experimental studies

“…One approach is to heat the spinline by hot air or laser, such as in melt blowing and melt spinning with online laser heating. [4][5][6] With the increase of spinline temperature, the fibers tend to be attenuated more and usually finer fibers can be achieved. However, the fibers created from melt blowing are typically discontinuous with short fiber length.…”