Superstructure and mechanical properties of nylon 66 microfiber prepared by carbon dioxide laser‐thinning method

Abstract

Nylon 66 microfibers were obtained by a carbon dioxide (CO 2 ) laser-thinning method. A laser-thinning apparatus used to continuously prepare microfibers consisted of spools supplying and winding the fibers, a continuous-wave CO 2 -laser emitter, a system supplying the fibers, and a traverse. The diameter of the microfibers decreased as the winding speed increased, and the birefringence increased as the winding speed increased. When microfibers, obtained through the laser irradiation (at a power density of 8.0 W cm Ϫ2 ) of the original fiber supplied at 0.23 m min Ϫ1, were wound at 2000 m min Ϫ1 , they had a diameter of 2.8 m and a birefringence of 46 ϫ 10 Ϫ3 . The draw ratio calculated from the supplying and winding speeds was 8696ϫ. Scanning electron microscopy showed that the microfibers obtained with the laser-thinning apparatus had smooth surfaces not roughened by laser ablation that were uniform in diameter. To study the conformational transition with winding speed, the changes in trans band at 936 cm Ϫ1 and gauche band at 1136 cm Ϫ1 were measured with a Fourier transform infrared microscope. The trans band increased as the winding speed increased, and the gauche band decreased. Young's modulus and tensile strength increased with increasing winding speed. The microfiber, which was obtained at a winding speed of 2000 m min Ϫ1 , had a Young's modulus of 2.5 GPa and tensile strength of 0.6 GPa.

Nylon 66 nanofibers prepared by CO2 laser supersonic drawing

“…The higher melting peaks are observed only in the DSC curves at p ch = 10 and 20 kPa where the nanofibers were obtained. Although we have reported the DSC behavior of N66 microfibers obtained by laser heating, the high‐temperature peak, as shown in Figure , has never been observed previously. The higher melting peak was also observed in the DSC curve of a PET nanofiber as previously reported .…”

High temperature zone‐drawing of nylon 66 microfiber prepared by CO2 laser‐thinning

“…The nylon 66 microfibers used for the high temperature zone‐drawing were prepared by irradiating the CO 2 laser to the original nylon 66 fiber. The CO 2 laser‐thinning method was described previously 5–9. The zone‐drawing in this study was continuously carried out in the form of a monofilament at the high temperature near the melting point (about 260°C).…”

“…A laser‐thinning method producing microfiber by irradiating a carbon dioxide (CO 2 ) laser to fibers was developed by us, and an apparatus for the CO 2 laser‐thinning is able to wind the microfiber as a monofilament, at winding speeds ranging from 100 to 2500 m min −1 . The laser‐thinning method has already been applied to a poly(ethylene terephthalate) (PET),5 nylon 6,6 isotactic polypropylene (i‐PP),7 nylon 66,8 and poly( L ‐lactic acid) fibers,9 and the microfibers with diameter range of 1.5–5 μm were obtained.…”

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

“…The CO 2 laser‐thinning method easily yields microfibers without using highly skilled techniques, and it is suitable for producing microfibers of various polymers at a small scale. The CO 2 laser‐thinning method was previously applied to poly(ethylene terephthalate) (PET),5, 6 nylon 6,7 nylon 66,8 isotactic polypropylene,9 and poly( L ‐lactic acid) (PLLA),10 and then their microfibers with a diameter of about 2 μm were obtained. SEM showed that the laser‐thinned (LT) microfibers had smooth surfaces not roughened by laser ablation, which were uniform in diameter.…”

“…Although the CO 2 laser‐thinning was characterized by the plastic flow accompanied by a molecular orientation and a strain‐induced crystallization, the mechanical properties of the obtained microfiber were insufficient because of the lack of the highly oriented amorphous chains and crystallites 5–10. Therefore, it was necessary to draw and anneal the microfiber obtained to improve its mechanical properties.…”