PET microfiber prepared by carbon dioxide laser heating

In preliminary experiments to optimize the condition of a laser heating, zone drawing for poly(ethylene terephthalate) (PET) fiber, a microfiber was prepared by a continuous‐wave carbon dioxide (CW CO 2 ) laser heating. CW CO 2 laser heating was carried out at an extremely low applied tension (σ a ) at a higher laser power density (PD) as compared to the optimum condition for the laser heating, zone drawing of PET fiber reported previously. The microfibers were obtained by CO 2 laser heating carried out at a PD of 15.8 W cm −2 and under a σ a of 0.66 MPa or lower. The diameter of the fiber decreased with a decreasing σ a and increasing PD. The smaller the diameter, the higher was its birefringence. The smallest diameter fiber obtained at σ a = 0.17 MPa at PD = 21 W cm −2 had a diameter of 4.5 μm and a birefringence of 0.112, and its draw ratio estimated from the diameter reached 3086 fold. Such a high draw ratio was not previously attained by any drawing method. In a wide‐angle X‐ray diffraction photograph of the smallest diameter fiber, indistinct reflections due to oriented crystallites were observed. An SEM micrograph of the smallest diameter fiber showed a smooth surface without any crack and was uniform in diameter.