Study On The Synthesis Of Modified Aromaticpolysulfonamide And Preparation Of Its Fibers

Aromatic polysulfonamide fiber(PSA)is a high performance fiber which is independently developed and has intellectual property rights in China.It has excellent properties such as high temperature resistance,corrosion resistance,flame retardant and so on.Therefore,expanding the variety of polysulfonamide fiber and promoting the development of polysulfonamide fiber are of great significance for the research of the field of high temperature resistant fiber in China.The industrial production of polysulfonamide is made of terephthaloyl(TPC)and-3,3’,4,4’-diaminodiphenylsulfone(3,3’-DDS,4,4’-DDS)by low temperature solution polymerization and it has high cost.The aim of this paper is to use m-phenylenediamine(MPD)to replace part of 4,4’-DDS to prepare modified aromatic polysulfonamide fiber and develop a new kind of high temperature resistant material.The process of polymerization and spinning process were studied in the laboratory to provide theoretical basis and experimental guidance for industrial production.Firstly,the modified polysulfonamide was prepared by low-temperature solution condensation,and its structure was characterized by nuclear magnetic resonance hydrogen spectroscopy(~1H-NMR)and Fourier infrared spectroscopy(FT-IR).Differential scanning calorimeter(DSC)and thermal weight loss analysis(TG)were used to study the thermal properties and thermal stability of modified polysulfonamide.The results show that the copolymer structure of the modified polysulfonamide is consistent with the expected design;The glass transition temperature(Tg)of the polymer is 286.73℃,and the thermal decomposition starting temperature(Td)is 459℃,indicating that the modified polysulfonamide has better thermal stability.In order to obtain a modified polysulfonamide with higher molecular weight,the effect of condensation process on its viscosity was studied.The results show that the reaction time is above30min,the reaction initiation temperature is 5℃,the monomer concentration is 0.65 mol/L,the TPC/diamine is 1.001:1.000,the rotation speed is 600 r/min,and the solvent is gradually added in8:2.It can synthesize modified polysulfonamide polymer with inherent viscosity of 2.12 dL/g.Secondly,the modified polysulfonamide fiber was prepared by wet spinning.Scanning electron microscope(SEM)was used to observe the morphology of the fiber.The fiber strength tester measured the mechanical properties of as-spun fiber and heat-drawn fiber.The overall fiber orientation was measured by using the sound velocity orientation method(SVM),and the crystallinity of the fiber was measured by using X-ray diffraction(XRD).The effects of wet spinning process including coagulation bath concentration,nozzle draw ratio,water bath draw ratio,hot draw temperature and hot draw ratio on the structural properties of the as-spun fibers and hot drawn fibers were investigated.With the increase of coagulation bath concentration and negative stretching of nozzle,the structure of as-spun fiber becomes more compact and the breaking strength increases.As the stretching of the hot water bath increases,the breaking strength first increases and then decreases.The best wet spinning process is determined as follows:the concentration of the coagulation bath is 50%,the nozzle stretching is-60%,and the water bath stretching is 2 times.During the hot drawing process,as the hot drawing temperature increases,the breaking strength、crystallinity、orientation of the fiber first increases and then decreases.As the hot draw ratio increases,the breaking strength and crystallinity of the fiber increase first and then decrease,while the degree of fiber orientation has been increasing.The best hot drawing process is:drawing temperature is 320℃,hot drawing is 2 times,and the breaking strength of the fiber obtained 3.68 cN/dtex.Finally,the performance as-spun fiber and heat-drawn fiber of modified polysulfonamide with different inherent viscosity were studied.The results show that the breaking strength of as-spun fiber is 1.42 cN/dtex～2.16 cN/dtex,and the breaking strength of hot drawn fiber is 2.62 cN/dtex～3.58 cN/dtex.The mechanical strength of as-spun fibre and hot drawn fiber increases with the increase of inherent viscosity.According to XRD the crystallinity of the as-spun fiber was between 6.2%and 7.4%,and the crystallinity of the heat-drawn fiber was between 8.2%and 11.4%.The glass transition and the orientation temperature of as-spun fibre and heat-drawn fiber increases with the increase of viscosity.The as-spun fibre Tg is between 288℃～303℃,and The heat-drawn fiber Tg is between 293℃～313℃.