| Ultrahigh molecular weight polyethylene (UHMWPE) fibers have plenty of excellent properties and have been used widely in the field of industry and other special areas. Gel-spinning and then ultrahigh-drawing is a mature and early industrialized method to produce UHMWPE fibers. In this paper, the domestic mineral oil is employed as solvent, UHMWPE fiber with excellent mechanical properties is prepared by dissolving, gel-spinning, extracting and ultrahigh drawing. The relationship between fiber structure and properties is investigated deeply by means of varies of measurements.The preparation of uniform UHMWPE solution is the chief task of gel-spinning. The dissolving of UHMWPE power includes two process of swelling and dissolving, the optimum swelling temperature is related to the solvent character and fully swelling needs a period of time. The viscosity of solution increases with the increasing of solution concentration and with the decreasing of solution temperature, and E of solution increases with the increasing of solution concentration. The dissolving capability of mineral oil is better than kerosene oil.The extracting mechanism of UHMWPE gel fiber is the di-diffusion of solvent and extracting agent. The computational formula for diffusion coefficient (D) of fiber solvent is as follows:During the process of di-diffusion, D is related to the variety of extracting agent and extracting mode, D increases with the increasing of extracting bath ratio and temperature. In this paper, the extracting mode is carried out with the help ofultra-sonic, halohydrocarbon and dimethyl benzene are selected as extracting agents by means of measurements of D. When the extracting agent is halohydrocarbon, the optimum extracting time is 5.5 minutes, the optimum drying temperature and time are 20℃ and 3 minutes respectively, while for dimethyl benzene, the optimum extracting time is 6 minutes, the optimum drying temperature and time are 25 ℃ and 12 minutes respectively, the optimum bath ratio of two extracting agent to gel fiber are both 20:1. UHMWPE gel fiber should be extracted several times to remove the solvent thoroughly. In order to prevent the volatility of extracting agent, halohydrocarbon can be sealed with a layer of water, dimethyl benzene can be mixed with water to prepare O/W emulsion, which is used as composite extracting agent, whose effective extracting component is dimethyl benzene.In order to obtain the highest drawing ratio, UHMWPE gel fiber should be extracted and dried under constrained state, and the solvent in gel fiber should be removed thoroughly. The drawing velocity of extracted UHMWPE fiber is not suitable to be too high and there exist an optimum range of drawing temperature. Multi-step and multi-stage drawing is an effective method to obtain ultrahigh drawing, the drawing temperature should be increased step-by-step, and there exist an optimum range of drawing ratio in every step.The relationship between structure and properties of gel-spun UHMWPE fibers during drawing process is investigated in details with varies of measurements. The results indicate that: (1) The mechanical properties of fibers increase sharply with the increasing of drawing ratio, and the increasing trend is slower when the drawing ratio exceeds about 30. (2) As the drawing ratio increases, fiber structure become more regular and denser, the orientation and crystallinity increase, the average crystal size vertical to drawing direction decrease, while the long period of fibers increases. The changing trends of above four parameters all become equilibrium when the drawing ratio exceeds about 30. (3) In DSC thermograms, unconstrained fibers show only oneendothermic peak, while constrained fibers show three different endothermic peak, which are melting peak of orthorhombic crystals, the phase transition peak of orthorhombic to hexagonal and melting peak of hexagonal crystals respectively, the equilibrium Tm and Hm increases with the increasing of drawing ratio; (4) As the drawing ratio increases, the...
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