Preparationof PET Fibridby Precipitation Methodandits Paperpermaking Property

In recent years, with the overall development of social economy and industry, high-performance, functional, differential polyester (PET) fiber is becoming the important structure material and base material.Melt spinning and wet spinning as two commonly used methods of synthetic fiber molding technology both have the problemsof thatthe equipment is complex and the costis highly.Precipitation method as a branch of wet spinning, its application field is continuously developing and improving.Fibrid made with precipitation method which is that a certain concentration of polymer slurry injects in high speed shearing coagulant, droplets is gradually elongated under the action of high speed shear force, deformed, frizzed, fibrillated in the end. All the performance (surface topograph, size distribution, surface area,crystallinity, thermal property) of fibrid can be regulated and optimized by precipitation process. Compared with traditional preparation process, precipitation process leaves out the cutting and fibrillation process, which offers a new approach to the preparation of fibers.In this paper, PET polyester chip was used as the raw material, which was prepared to PET fibrid with precipitation method.The influence of the factors such as the concentration of PET slurry, the drop rate of PET slurry, shear rate, shear time and the kind of coagulant on the physicochemical property such as surface topograph, size distribution, surface area, crystallinity, thermal property of PET fibrid was studied, and the process of precipitation wasoptimized. PET fibrid and PET chopped fiber were made into PET papers,and the paper-making propertyofPET fibrid were studied, which set the foundation of the solution of PETpolyester chip and the process of precipitation.In the analysis of physicochemical properties of PET polyester chips, phenol/tetrachloroethane were as solvent, molecular weight and intrinsic viscosity were tested with Ubbelohde viscometer; thethermal stability were tested by TG and DSC; dissolving condition of PET polyester chip in phenol, tetrachloroethane and phenol/tetrachloroethane binary co-solvent under appropriate temperature and time were detected.The crystal of PET slurrywas observed by polarized light microscope (POM), the viscosity wastested by rotary viscometer and ubbelohde viscometer,and the coagulation values were also tested.The results showed that PET slurry was a kind of polymer liquid crystals, its viscosity decreased with the increasing of temperature, increased with the increasing of the concentration of slurry and the shearing rate, and it was a kind of shear thickening dilatant fluid which can exist under a certain condition.The anisotropic of PET slurry made it easilyto form the crystal of PET fibrid under the shear force in the process of precipitation.In the process of precipitation, slurry concentration, shear rate, shear time, the slurry droplet acceleration, and the kind of coagulant were optimized. PET fibrid prepared under different conditions were observed under optical microscope, scanning electron microscope, and specific surface area, Screen classification analysis, thermogravimetric analysis, XRD analysis of PET fibrid were also studied. It found that it had big difference between the morphology of the makert PET pulp and PET fibrid, makert PET pulp was evenner than PET fibrid, and the thermal stability was higher than PET fibrid; the specific surface area of PET fibrid was much bigger than the makert PET pulp, it was the same to the crystallinity.Makert PET pulp and PET fibrid prepared under different conditions together with the chopped PET fiber(at the rate of 3:7,4:6,5:5,6:4,7:3) were made into paper respectivly, the paper-making property of them were measured. Under the condition of the best ratio 5:5, PET fibrid prepared under different precipitation conditions all could be made into papers. The tensile index of the paper made with PET fibrid was 34.0N·m·g-1, the tear index was 27.5mN·m2·g-1, the burst index, was 5.19KPa·m2·g-1, The tensile index of the paper made with the makert PET pulp was 31.9N·m·g-1, the tear index was 18.0mN·m2·g-1, the burst index, was 4.3KPa·m2·g-1, the paper-making property of PET fibrid was better than the makert PET pulp.