The Structure of Poly(ethylene terephthalate) Fiber Drawn with CO2 Laser Heating

Poly(ethylene terephthalate) fibers were continuously drawn to high draw ratios under heating by CO2 laser irradiation. The structure of the drawn fiber was analyzed based on measurements of refractive index, wide-angle x-ray diffraction, and small-angle x-ray scattering. The average refractive index, birefringence, crystallite size, crystal orientation and the long period of the fiber structure were found to increase with the draw ratio. However, for fibers drawn to a final ratio of 6:1, neither the diameter of the laser beam, the feed speed, nor the laser power affected the fiber structure appreciably. The crystallite size and long period of a fiber drawn to a ratio of 4:1 were both altered more after annealing at fixed fiber length than for the 6:1 fiber. The lamellae structure inclination angle of samples drawn to both 6:1 and 4:1 was about 60°, decreasing after annealing to 50° for the 6:1-drawn samples and 30° for the 4:1-drawn samples.