Preparation, Structure And Properties Of Pan Fibers Blended With Different Tg Copolymers

Polyacrylonitrile fiber, as one of the three synthetic fibers, has lots of excellent characteristics such as bulkiness, warmth, softness, weather ability and so on. Based on these advantages, it has been widely applied in apparel, home furnishings and industrial fabrics. In recent years, with the development of synthetic fiber industry and increasing demands for functional fibers, the research and development of functional PAN fibers with hydrophilic, antistatic, antibacterial, flame-retardancy, acid-dyeable and low-temperature dyeing property led one of the most important trends and drawn widespread attention.Nowadays, the industrial production of the functional PAN fibers modified with inorganic materials has been realized. But the industrial production of the functional PAN fibers modified with organic materials still faces challenges. The main reasons affected the functions and spinning ability of these PAN fibers are listed as follows:(1) the dissolution of the small organic molecular during the molding process;(2) phase separation of macromolecular in the PAN matrix.To solve the problems above, this paper raises a new method called "Homogeneou" blending to prepare functional polyacrylonitrile fiber. Taking sodium thiocyanate(NaSCN) as solvent, we blend the polymerB, an acrylonitrile copolymer with low glass transition temperature at 59.6?, with conventional polyacrylonitrile(polymerA)(Tg=91.1?) in different proportion. These two polymers showed good compatibility since they were acrylonitrile copolymers in nature, and could form a stable spinning dope. In this work, the rheological behavior of polymer A/B/NaSCN dope, wet spinning process and the structure and properties of the blending fiber was studied. The main conclusions are given as follows.(1)The rheological behavior of polymerA/B/NaSCN dope was discussed to support the following spinning. The steady state testing showed that: polymerA/B/NaSCN system was a non-newtonian fluid. Increasing content of polymerB resulted in the increase of the dope's viscosity. Phase separation between polymerA and polymerB were formed when the polymerB content reach 20% and the dope's viscosity can be 4 or 5 times as large as conventional PAN dope. The critical shear rate moves to lower shear rates. This phenomenon suggested that the proportion of polymerB in the dope should be carefully adjusted to ensure the spinning ability of the dope. Meanwhlie, the non-newtonian index of the dope decreased a lot when the polymerB content reach 20%. Compared to the conventional PAN dope, the prepared dope by blending polymerA and B showed low viscous activation energy. The sipinning ability was enhanced by reducing the temperature-dependence of dope. The dynamic testing of the dope illustrated that the high content of polymerB resulted in gelation. Whersas, the increasing temperature decreased the degree of gelation of the dope. In oder to optimize the spinning process, the spinning temperature was determined to be 60 ?.(2) The spinning process for prepare PAN fibers blended with different Tg copolymer was studied. The optimum spinning condition was described as follows: coagulation bath(NaSCN aqueous solution) temperature was 10?,concentration of the coagulation bath was 11%, while the jet stretch ratio was 0.9, and the first water bath draft ratio was 1.5 times, bath temperature was 60?,in the second boiling water drawn, the maximum A/B blending fiber draw ratio was 6, 9 times the total draft of A/B blending fiber.(3)The strcture and property of the blending PAN fiber were studied. The results demonstrated that polymerA and polymerB were physical blending in the fiber. The compatibility of these two polymers were good with low polymerB content and polymer B distributed homogeneously in the matrix phase polymerA. when the polymerB content reach 20%, phase separation took place between the two polymers; The blending PAN fiber showed good thermal stability at low temperature. But its high-temperature resistance slightly decreased with the increasing content of polymerB.(4)The low temperature dyeing properties of PAN fibers blended with different Tg copolymer were studied. The results showned that: compared to the conventional PAN fiber, the blending fiber have excellent low-temperature dyeing performance. The dyeing equilibrium uptake of blending fiber can reach 90% at 70? or 65?, 30? lower than the conventional PAN. The optimum low-temperature dyeing process was described as follows: dye concentration was 1%owf, dye bath PH was 5,constant temperature dyeing at 70? for 40 min. The isothermal kinetics was studied and the dyeing data of after fitting accorded with the Langmuir adsorption mechanism.