Preparation And Performance Of Industrial Polyester Yarn With High Strength And Elongation

This paper has analyzed the current situation and prospect of the differential polyester industrial yarn. The research focused on the improvement of the current production process in order to develop a kind of polyester industrial yarn with the performance of high strength, large elongation and low shrinkage, which can be directly applied in the supporting layer of water treatment filter membrane. Embarking from three aspects, i.e. solid phase polymerization process of polyester chip, spinning process and fiber performance, we delved into the influence of the reaction temperature and reaction time during the solid phase polymerization process and the melt temperature, hot roller speed and temperature during the spinning process on the spinning production. Experiments were performed by the production equipments, physical properties testing instruments and chemical analysis instruments in the provincial enterprise institute, Zhejiang Halead New Materials Co., Ltd. The solid phase polymerization and melt spinning during the production process of polyester industrial yarn for water treatment were studied, and the production of the polyester industrial yarn for water treatment was successfully realized by optimizing the process parameters.The PET chip with the characteristics of high viscosity, low moisture content and low end carboxyl content was prepared by the solid phase polymerization of PET raw material with low viscosity using the continuous solid-phase polymerization equipment. The paper mainly investigated the influence of solid phase polymerization temperature and time on the intrinsic viscosity. The results indicated that the intrinsic viscosity increased with the increase in temperature and reaction time. Based on the comprehensive consideration of cost factor, the optimization of solid phase polymerization process is:crystallization temperature 160-170℃ and residence time 1-2 h, pre-crystallization temperature 210-210 ℃ and residence time 3-4 h, reaction temperature 210-220℃ and residence time 30-50 h. Under the optimum condition of polymerization process, the intrinsic viscosity of the prepared polyester chip increased from 0.675 dL/g to1.03-1.18 dL/g, the moisture content decreased from 0.04% to 0.015% and the end carboxyl content reduced from 24% to 12%. The crystallinity of polyester chip after the solid phase polymerization is 60-63%, which was tested by X-ray diffraction.The differential scanning calorimetry and capillary rheometer were used to investigate the non-isothermal crystallization kinetics and rheological properties of the prepared chip. The results indicated that the crystallization peak moved to a high temperature and got wide when the heating rate increased from 5 K/min to 40 K/min. The Jeriorny method demonstrated that the Avramin exponent (n) of the solid phase polymerization PET chip was 2.0-2.6 under different heating rates, which could speculate that the homogeneous nucleation and heterogeneous nucleation existed at the same time during the crystallization process. The rheological analysis results suggested that the melt showed sheared dilution behavior when the shear viscosity range was 200-10000 s-1 and its non-Newtonian index was less than 1. The flow activation energy was 71.78 kJ·mol-1 when the shearing rate was 200 s-1, and the flow activation energy was 36.57 kJ·mol-1 when the shearing rate was 1691.66 s-1. These results showed that the flow activation energy decreased with the increase in the shearing rate. Therefore, the temperature dependence of melt enhanced under high shearing rate, which was important for the temperature control in the spinning process.With high viscosity polyester chips as raw material, the PET industrial yarn was prepared by melt spinning, and the influences of melting temperature, spin-stretch ratio, stretching temperature and other factors on the fiber properties were investigated. The mechanical and thermal properties of the fiber were tested by fiber tensile tester, X-ray diffraction, drying oven and so on. The results indicated that the melt temperature had a greater influence on the spinnability. Moreover, the appropriate increase of the spin-stretch ratio was in favor of the increase in the breaking strength of the fiber, and the setting temperature has a decisive influence on the dry-hot shrinkage of the fiber. The final optimum process conditions were determined as follows:extrusion temperature 290-300 ℃, spinning rate 450-2600 m/min, stretching-setting temperature 230-240 ℃. The properties of the prepared fiber were as follows:fiber denier 467 ±9 dtex, breaking strength≥7.0 cN/dtex, elongation at break 24 ± 2%, dry-hot shrinkage 4.9% and high-grade rate above 95%, which can meet the customer requirements of high strength, high elongation and low shrinkage performance. The products have been sold to the European famous film company, making a good economic benefit.