Application Of Fundamental Of Melt Spinning And Development Of Polymer Optical Fiber

On basis of fundamental and mathematical model of melt spinning,in combination of experimental results,the flow characteristic and mechanics of orientation and crystallization in rapid deformation of polymer were investigated phenomenologically.The extensive models of melt spinning were established through fitting and optimizing parameters.The models were verified and become the guidance of new technologies and products.Besides,traditional melt spinning was introduced to the process of polymer optical fibers and the spinnability of these optical polymers was discussed,as well as the optimized spinning conditions.Different kinds of polymer optical fibers were directly obtained via melt spinning which open the door to high volume low-cost production of polymer optical fibers.Converse-fit method was introduced to obtain the unknown model parameters by use of experimental results of final products that can be easily get through experiment in order to obtain the integral models,acting as guidance for practical production.The phenomenological melt spinning models were used to describe the thin-filament, steady-state model of poly(ethylene terephthalate)(PET) melt spinning with relatively integral model parameters and the filament temperature,velocity,tension, crystallinity and birefringence along the spinning line as well as the distribution of radial orientation and temperature were depicted by use of the fourth order Runge-Kutta algorithm.The phenomenological melt spinning models were successfully applied in the model of poly(trimethylene terephthalate)(PTT) fiber and different shape fibers.The method,in principle of the box complex algorithm was adopted to obtain stress-induced crystallization coefficient,strain-optical coefficient and some parameters related to elongational viscosity of poly(trimethylene terephthalate)(PTT) fiber.The vitrification distance as a function of the take-up velocity and mass throughput was formulated and the effects of spinning conditions on the properties of as-spun fibers as well as the effect of viscoelasticity on take-up velocity had been calculated and discussed.Appropriately controlling the spinning condition such as throughput,spinning temperature,quench air temperature,quench air velocity and draw ratio,is very convenient to the growth of crystallinity and birefringence.The optimized process parameters are set as throughput of 770g/min,quench air temperature of 25℃,draw ratio as 1.02,spinning temperature from 250 to 253℃and spinning velocity from 1100 to 1130m/min.The circular PTT staple is superior to other similar products with high tensile stress,good elongation and excellent elasticity.On the other hand,variety of cross-sectional shape along the spin line was incorporated adopting a formulation in which energy dissipation by viscous flow in the plane perpendicular to the fiber axis by the introduction of shape index related to spinneret design and revised coefficient of elastic effect.Diverse vitrification distances due to different quench air conditions had been depicted for the first time and the influence of processing parameters on the cross-sectional shape was discussed and verified.Different types of shape fibers,such as trefoil,triangle,crisscross,are produced and "U" shape filament had been taken as example to explain the method of development of new products.Irregular profile of "U" shape filament offers fabric with bulk effect,improved luster,handing,good moisture permeability and air perviousness.The T-shirt from this filament have been proved to have excellent anti-fuzzing and anti-pill,great strength,super fastness to washing,perspiration and rubbing and wonderful comfort and hygienic.Besides,the phenomenological melt spinning models were introduced in the industrial production of PET staple fiber successfully.The models for melt transportation were classified into six categories,pipe,booster pump,melt filter,static mixer,metering pump and spinning pack by investigation of melt flowing and device structure.The sub classified models of retention time,pressure drop,temperature enhancement and melt heat degradation were obtained according to the each melt model.The effects of melt throughput,intrinsic viscosity,pressure,melt temperature and circular thermal coal temperature on them were analyzed and corresponding proportions had been obtained.Simulation results of melt transportation show that major part of temperature increase are focused on the booster pump,melt filter and spinning pack,which also results in main decrease of pressure.However,long transportation pipe and melt filter lead to most proportion of viscosity degradation, which increases under low initial intrinsic viscosity and temperature,as well as high initial pressure and throughput at the same strength of final product.The intention time are mostly up to initial throughput as a function of first order exponential decay. In the melt spinning process,accounting for air drag as well as the heat uptake, distribution models of the quench air temperature and the quench air velocity suitabl to multifilament of PET staple fiber were presented on basic of fundamental of single filament model.The temperature,velocity,quench air velocity and quench air temperature of filament located at different position as function of spinning path were investigated and the relationship among spinning condition,structure and property of as-spun fibers were formulated by the experimental results of birefringence and elongation.The PET staple fiber simulation system was obtained by further understanding of machine operating and spinning parameters from 60t/d half-closed and 165t/d fully closed circular air-blowing spinning device of Yizheng Chemical Fiber Co.,Ltd.The flowing melt in the transportation pipe was pictured vividly and varieties of melt temperature,pressure and viscosity in the whole process,especially near the main equipments,were effectively predicted.The properties of melts and as-spun fibers were predicted and spinning conditions were optimized within 10 percent error.In general,with this set of simulation system,the optimization of current spinning condition,guidance of new product and prediction of maximum capacity are easily carried out.Three methods were introduced to produce polymer optical fiber,including holey fiber through multi-hole spinneret,holey fiber from removing sea component from bi-component fiber and sea-island fiber of two polymers with different refractive index.Good-quality holey fiber from multi-hole spinneret is a careful balance between sophisticated technology of spinneret design,optical polymer with excellent thermoforming properties and transparency and proper spinning conditions especially quench air condition.The Polymethyle methacrylate(PMMA) fiber was extruded successfully and the optimized temperature and spinning velocity are from 210 to 215℃and from 200 to 300m/min respectively with maximum holey number of 15.The water-soluble polymer Exceval developed by Kuraray specifically for the melt-molding application was introduced as island(core) component,while PETG (Polytetrafluoroethylene) which is one of the toughest transparent materials with excellent thermoforming properties acted as sea(sheath) component.Under optimized temperature of 225℃,the sea-island and sheath-core fibers were obtained.The water dissolving condition should be above 95℃to ensure relatively low residual rate of Exceval.Most of the Exceval were removed from bi-component at condition of 95℃hot water for 6 hours.However,the severe deformation of the PETG is still unavoidable due to the relatively lower glass temperature(80℃) compared with dissolving conditions of 95℃hot water and longitudinal unevenness of dissolution still exists in every experimental filament.For sea-island filaments,the outer sea component is too thin to support the whole structure,as a result,the outer sea component collapses and severely destroy the whole structure.The effective ways to improve the quality of holey filament are rapid cooling to reduce the crystallization, new sea-island or other holey spin pack with thick outer sea component to ensure integrity of the structure and new water soluble material with lower water dissolving conditions and better spinnability.As a substitute,ESTAMAN modified PET(AQ55S) has advantage of spinnability and water soluble.Part of AQ55S in PETG/AQ55S sheath-core fibers dissolved below glass temperature of PETG(70℃) and most of them were removed at temperature of 90℃.For PETG/AQ55S sea-island fibers,some of the outer islands were removed at 90℃,while inner islands still need more time and higher temperature to get rid of.In our opinion,brand new water soluble materials with excellent water solution and spinnability of melt spinning will be the best way to offer good quality multi-hole filament.L40(PMMA) and PETG with refractive index of 1.57 and 1.49 respectivel were introduced as component of sea-island and sheath-core fibers.Some fibers of different ratios were produced with maximum light transmitted light of 55cm from infrared thermometer for sheath-core fiber.And the majority light transmitted lengths of sheath-core and sea-island fibers are 25cm and 10cm respectively.The limitation of light transmitted length of single polymer via melt spinning mainly results in the short transmitted length.Designing the spinneret with relatively large holes,rapid cooling device and multi-drawing with low temperature and ration may help to improve the transmitted length.