Study On Preparation Technology Of Uhmwpe Solution And Hollow Fiber

Ultrahigh molecular weight polyethylene (UHMWPE) has the organic flexible molecular chain. The UHMWPE fiber which has the linear chain structure and high orientation is one of the high performance fibers and widely applied to many fields. The gel-spinning and ultra-drawing method is used in the industry.The most studied about the hollow fiber is the hollow fiber composite membrane and tri-dimensional crisp warm hollow fiber, but spinning UHMWPE hollow fiber is not reported. It is significant for army to lighten the equipments and the weight of the UHMWPE hollow fiber which is used armored clothing can be reduced largely. The good performance hollow fiber was prepared by dissolving UHMWPE powder in mineral oil, gel-spinning, extracting and ultra-drawing. The relationship of fiber's structure and properties was investigated by varied measurements.The preparation of uniform UHMWPE solution is the chief task of gel-spinning. The UHMWPE powder was first swelled at the optimum temperature 130℃ for 40-60 minutes, then was dissolved at 180℃ in different equipments. The result showed that the solution used bykneading machine is better.The rheological properties of polymer are the basis to formulate process and choose equipments. Finding out the effect of concentration, molecular weight and temperature how to influence the rheology of spinning solution may provide basis for preparing appropriate spinning solution and choosing spinning process. The investigation to different spinning solutions of varying concentration and molecular weight were tested on the ARES rotary rheometer TA Corporation produced. The results showed that UHMWPE solution is pseudoplastic liquid which viscosity drops with cutting force increasing. The apparent viscosity of spinning solution rja was reduced;the Non-Newton parameter (n) was increased;A 77 dropped while the temperature rising. The apparent viscosity rja of spinning solution was increased, the Non-Newton parameter (n) was reduced, the value of A 77 was increased and the viscous flow activating energy was increased while the solution concentration and molecular weight were increased. Molecular weight influenced the viscous flow activating energy of the solution more obviously than the concentration.Because the preparation of UHMWPE solution and spinning all carried on in a high temperature continually, UHMWPE is very easy to decompose by heated and oxidized. According to calculating molecular weight by measuring the viscosity of spinning solution, the function ofantioxidant during dissolving process had been characterized. In this paper the influences of 1010 antioxidant and IRGANOX B225 antioxidant from Ciba, their concentrations and heating times were compared. The results showed that UHMWPE decomposed greatly with the temperature and heating times increasing during dissolving. After adding antioxidants the decomposition had been prevented effectively and the function which they suppress the decomposition also enhanced with the antioxidant content increasing. As the content is equal, the IRGANOX B225 antioxidant from Ciba is better than 1010 antioxidation for UHMWPE. The heating time during UHMWPE dissolving should be controlled within 100 minutes to keep the molecular weight of UHMWPE large enough and the prepared solution suffice spinning high modulus fiber.After prepared even spinning solution the smooth and even gel fiber was spun from the small self-restraint spinning machine using the double-rings-tubular-shaped spinneret with 130°C~ 140°C mineral oil as center filling, controlling the flux, temperature of mineral oil and spinneret and coiling speed, and finally was curdled in the ice-water bath.When dimethyl benzene was selected as extracting agent of gel fiber, the diffusion coefficient (D) which was carried on in ultra-sonic was bigger than the D which was settled. The ultra-sonic wave accelerates the diffusion movement of the molecular. D is the average diffusioncoefficient within the extract time (t), so D increases along with the time (t) reduced, and diffusion coefficient (D) of solid gel fiber is bigger than that of the hollow gel fiber.The relationship between structure and properties of gel-spun UHMWPE fibers during drawing process was investigated by varies of measurements. The results indicated that as the drawing ratio increased the intensity and module of the fibers was increased, the rupture-stretched ratio was reduced, fiber structure has became more regular and denser, the orientation and crystallinity was increased, and the creep-resistant property was increased, the fiber molecular-chain was oriented along the drawing direction sharply, and the sonic-oriental parameter was increased and become equilibrium finally when the drawing ratio increases. The result of analyzing DSC thermograms indicated that the unconstrained fiber had shown only one endothermic peak, while constrained fiber had shown two shoulder-peaks around the main endothermic peak. This indicated that when heating constrained fibers there were a little phase transition from orthorhombic crystals to hexagonal crystals. The equilibrium Tm and AHm has increased with the increasing of drawingratio.New ideas mainly brought forward in this paper are: ?New dissolution equipment was selected and uniform UHMWPE spinning solution was prepared;(2)The oxidation mechanism of UHMWPE wasdiscussed by comparing function of different antioxidants during dissolving process;(3) The spinning process of UHMWPE hollow fiber was investigated, and the intensity of the prepared hollow fibers is more than 20cN/dtex.