Correlation between the tensile properties and network draw ratio of CO2-laser-heated drawn poly(ethylene terephthalate) fibers

Low-orientation and amorphous poly(ethylene terephthalate) fibers were drawn continuously with heating by carbon dioxide (CO2) laser radiation. The tensile properties were examined in terms of the birefringence and network draw ratio, which was estimated from the strain shift of true stress-strain curves. Two drawing forms, neck drawing with a draw efficiency (the ratio of the network draw ratio to the actual draw ratio) of about unity and flow drawing with a draw efficiency of about zero, were found to be stable in the continuous drawing process. Meanwhile, any draw-efficiency value between zero and unity could be obtained in the batch-drawing process. The object whose orientation was estimated by the network draw ratio differed from that estimated by birefringence. Two linear relationships were found, between the network draw ratio and tensile strength and between the birefringence and initial modulus. The true stress at breaking increased with the network draw ratio of the CO2-laser-heated drawn fibers, and when the draw ratio exceeded 5.0, it became higher than that for batch-drawn fibers. (C) 2003 Wiley Periodicals, Inc.