The Study On UHMWPP/UHMWPE Gel System And Its Alloy Fiber

As one of the 3-high-performance fibers of the modern world, Ultra-high molecular weight polyethylene (UHMWPE) has been widely used in a variety of areas because of its excellent properties, and its output has also soared recently. As the UHMWPE fibers are gradually known to users, its property defects exposed. For example, the product shape from the fiber would be changed severely especially for the products being used for a long period of time under tension; the application temperature is usually below 70°C, and the product structure could be deformed and its mechanical properties could deteriorate if the products are used beyond this temperature; The adhesion is poor, there could be phase separation between the interfaces when it is blended mechanically with other materials to improve its properties. These intrinsic drawbacks of the UHMWPE constraint its further application greatly.After comprehensive study on the mentioned 3 defects above, we explored a new way to improve them and applied for 3 patents (they are Publication Number: CN101046005, Application Number: 200710044032.1/200710046743.2). PP/PE blends is thermodynamically miscible and PP has higher thermo-stability, lower creep and better adhesion than PE. If UHMWPE is blended with UHMWPP before process of dissolving and then dispersed in the dissolving system in molecular scale, the UHMWPE would form into micro-fibers and serve as the frameworks for UHMWPP matrix after gel-spinning and hot-stretching. As a result, the tensile strength and Young’s modulus of the alloy fiber could be enhanced dramatically.It is very difficult to take the processing under control because the UHMWPP/UHMWPE gel system is of high viscosity and sensitive to heat. Therefore, the dynamic rheological behavior measurement of the gel system has been studied in this paper. It was found that the gel system with 3wt% UHMWPE presents the best comprehensive properties: when the temperature is 180°C, the system has higher storage modulus, higher loss modulus, lower loss tangent and activation energy.The non-isothermal crystallization kinetics and crystallization characterization of the alloy fiber have also been investigated. It showed that the UHMWPE acted as nucleating agent; the nucleating temperature, crystallization speed, crystal perfection, brittleness and crystallinity of the alloy fiber have been improved greatly.The study on the relationship between structure and properties of the alloy fiber elucidated that the polymers were in good compatibility, the toughness of the alloy fiber and the adhesion between the interfaces were improved dramatically. It was found that when the content of UHMWPE was higher than 3wt%, the UHMWPE served as framework of the alloy fiber and the mechanical properties were better. Theα-crystal relaxation temperature of UHMWPP was determined as 100-120℃, and the alloy fiber usually exhibited better draw-ability as well as mechanical properties if it was drawn above this temperature. The mechanical properties of the alloy fiber were mainly depended on draw ratio and higher UHMWPE content usually resulted in alloy fibers with better draw-ability, mechanical properties as well as thermo-stability.