Abstract:

Objective In the mid-1980s， Allied Signal of the United States pioneered the development of high modulus and low shrinkage （HMLS） PET industrial yarns. Due to its features in high-end applicability， lightweight and green manufacturing， market demands for this high-performance fiber material have been continuously increasing. In addition to the ultra-high strength standard of more than 8.20 cN/dtex， stringent requirements for such fibers now encompass dimensional stability， high modulus， and low shrinkage characteristics.

Method Research on increasing viscosity via solid-phase polycondensation PET chips； controlling oil-free filament viscosity， optimizing melt pipe design to reduce viscosity， increasing spinneret hole count， and decreasing single-filament fineness. By selecting spinneret configurations， post-heater length and temperature， and cooling/forming methods， the draw ratio and spinning tension at the spinneret were enhanced， improving the orientation and crystallinity of PET filament yarn. Investigating draw-setting processes to optimize fiber orientation and crystalline structure， achieving the production of ultra-high-strength， high-dimensional-stability PET industrial yarn.

Results Increasing the viscosity of solid-phase polycondensation chips yields fibers with higher strength and modulus， but correspondingly higher dry heat shrinkage. High-viscosity chips produced at low temperatures over extended periods significantly outperform those produced at high temperatures for short durations. Maintaining a relatively high oil-free filament viscosity was proven crucial. When the oil-free filament viscosity reached 0.99 dL/g， the filament strength was 8.21 cN/dtex. Increasing the spinning speed was also found to enhance the dimensional stability of ultra-high-strength， high-dimensional-stability， high-modulus， low-shrinkage PET industrial filaments. Increasing the draw ratio of the spinneret led to the improvement of the modulus of ultra-high-strength， high-dimensional-stability， high-modulus， low-shrinkage PET industrial filaments. Moderately reducing the temperature of the component post-heater improved the strength and modulus of UHS-HMPS PET industrial yarns. Controlling the insulation zone length of the post-heater between 20 and 50 mm yielded favorable dimensional stability and production consistency in actual manufacturing. Producing ultra-high-strength， high-dimensional-stability， high-modulus， low-shrinkage PET industrial yarns via high-temperature tension-thermofixation enhanced fiber crystallization rates， and tension-fixation reduced macromolecular deorientation. Increasing hot-roller temperatures effectively minimized dry-heat shrinkage and improved dimensional stability. At a draw ratio of 1.69， the strength of the novel high-modulus， low-shrinkage PET industrial yarn with ultra-high strength and high dimensional stability reached 7.65 cN/dtex. When the draw ratio increases to 1.84， yarn strength increased to 8.21 cN/dtex， clearly demonstrating that increasing the draw ratio was beneficial yarn strength within a certain range. Comparative testing of the three-stage draw process （special first-stage cold draw followed by two-stage hot draw）， featuring secondary constant-speed high-temperature draw and single-stage shrinkage setting， versus the traditional standard two-stage draw with single-stage shrinkage setting and draw-setting winding process demonstrated that the former yields ultra-high-strength， high-dimensional-stability， high-modulus， low-shrinkage PET industrial yarn with superior strength and dimensional stability. The developed and mass-produced ultra-high-strength， high-dimensional-stability， high-modulus， low-shrinkage PET industrial yarn achieved all performance targets as expected.

Conclusion High-viscosity PET chips prepared via a low-temperature， extended

Key words: high-performance fiber material, PET industrial yarn, viscosity, high dimensional stability, spinneret draw ratio, draw-and-heat setting