Study On Polyimide Filament Fiber And Its Yarn Processing Properties

Polyimide(PI)is a polymer characterized by a polyimide ring.It has high temperature resistance,flame retardancy,radiation resistance,low dielectric constant and excellent chemical stability.It is widely used in aviation and aerospace.,microelectronics,nano,liquid crystal,separation membrane,laser and other fields.In recent years,polyimide fiber has been highly valued as a high-tech fiber,and it has a good application prospect in the field of functional and high-performance textile products.In this paper,polyimide primary filament(PI-1)and polyimide filament(PI-2)after hot stretching treatment were studied.Firstly,the basic physical and mechanical properties of the fiber were compared and tested.Analyze and study the effect of acidbase treatment on the structural properties of polyimide filament fibers.Then systematically study the twisting and sizing of PI filaments to improve the weaving properties of PI filaments.Finally,air deformation is used.Methods Several kinds of PI air-modified yarns were prepared and the yarn properties were tested and analyzed.Specific work includes: determine the the effect of heat drawn and setting process on fiber properties;study it's resistance to acid and alkali;Determine the critical twist coefficient of polyimide filament through the twist-strength performance test,simulate the natural fixed enthalpy,heat enthalpy,heat and moisture enthalpy to determine the optimal setting method of polyimide filament yarn;The basic properties of polyacrylate slurry for polyimide sizing were studied,and the sizing process was optimized to determine the optimum slurry solid content,sizing temperature and sizing speed.The sizing yarn was desizing with hot water and lye,respectively,to study the desizing performance of the polyimide filament;Six kinds of polyimide filament air-textured yarns with different super-feed ratios were processed,the most suitable processing parameters for textured yarns and was determined by tensile test,loop instability test and yarn structure morphology;In order to improve the problem of unclear opening and low manufacturing efficiency of PI filaments during weaving,fabric weaving was carried out by using polyimide-twisted yarn and sizing yarn as warp yarns respectively,and the improvement of weaving condition was discussed.In addition,in order to improve the phenomenon that the polyimide fabric is not full and the serious aurora,the polyimide air-textured yarn is used as the weft yarn to test the improvement on the fabric style.The results show that the hot drawing and setting treatment of polyimide filaments improves the crystallinity,orientation,mechanical and thermal properties of PI,and makes the fiber cross section more round,without changing the degree of imidization.The oil added during the processing makes the moisture regain of the PI increase,the specific resistance decreases,and the friction coefficient increases;the PI fiber has good acid resistance,the fiber surface is slightly etched after acid treatment,the degree of imidization and thermal properties are not affected,the loss of mechanical properties is small,after treatment,the degree of crystallinity and orientation decreased by 16.93% and 1.07%..After alkali treatment,the surface of the fiber is cracked,the degree of imidation reduced,the mechanical properties are seriously lost,the thermal decomposition temperature is still above 560 °C,the degree of crystallinity and orientation decreased by 49.67% and 1.34%;the critical coefficient of PI-2 is 105,and the maximum strength of PI twisted yarn is 90.4 cN/tex,the best method of setting is heat and moisture enthalpy;the performance of polyacrylate slurry is excellent,the optimum sizing process condition of polyacrylate slurry for polyimide filament is the slurry solid content of 15%,the slurry tank temperature was 70 ° C and the vehicle speed was 90 m/min;the polyimide sizing rate and the elongation reduction rate were 17.23% and 3.7%,respectively.The sizing rate is 8.6%,and the moisture regain is 3.5%.After the alkali desizing,the yarn structure is obviously loosened,the film is retreated,and the fiber is not etched,which maintains the excellent mechanical properties of the polyimide fiber;The polyimide air-deformed yarn has darker color and enhanced hairiness.Among them,the super-feeding ratio of 8/8 polyimide air-deformed yarn has the strongest felt,the distribution of the wire loop is relatively uniform,and the structural stability is high;Using PI twisted yarn as warp yarn can improve the problem of warping,but the unclear opening still results in low weaving efficiency.Using PI sizing yarn as the warp yarn can improved the opening,and the weaving efficiency is high.Using PI air textured yarn as the weft yarn can effectively improve the feel and aurora phenomenon of the PI fabric.