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Various processing technologies for ultra high molecular weight polyethylene

Jun 28, 2019

Processing of ultra-high molecular weight polyethylene Because the viscosity of the ultrahigh molecular weight polyethylene (UHMW-PE) in the molten state is as high as 108 Pa*s, the fluidity is extremely poor, and the melt index is almost zero, so it is difficult to carry out the general machining method. machining. In recent years, the processing technology of ultra-high molecular weight polyethylene (UHMW-PE) has been rapidly developed. Through the transformation of ordinary processing equipment, ultra-high molecular weight polyethylene (UHMW-PE) has been developed from the initial press-sintering forming to Extrusion, blow molding and injection molding as well as other special methods of forming. 1. Extrusion modification processing   Extrusion molding equipment mainly includes plunger extruder, single screw extruder and twin screw extruder. The twin-screw extrusion uses a co-rotating twin-screw extruder. In the 1960s, most of the plunger extruders were used. In the mid-1970s, Japan, the United States, and West Germany developed a single-screw extrusion process. Japan’s Mitsui Petrochemical Co., Ltd. first achieved the success of round bar extrusion technology in 1974. At the end of 1994, China developed a single-screw extruder for Φ45 ultra-high molecular weight polyethylene (UHMW-PE). In 1997, it achieved the success of the industrial production line of Φ65 single-screw extruded pipe.    Ultra-high molecular weight polyethylene (UHMW-PE) processing, when the material is extruded from the die, due to elastic recovery, a certain retraction, and almost no sagging phenomenon, it is a hollow container, especially The blow molding of large containers, such as fuel tanks and vats, creates favorable conditions. Ultra-high molecular weight polyethylene (UHMW-PE) blow molding can also lead to high-performance films with balanced strength in the longitudinal and transverse directions, thus solving the problem that HDPE films have long been inconsistent in the longitudinal and transverse directions and are prone to longitudinal damage. 2. Solvent-based extrusion spinning process The preparation of high-strength, high-modulus polyethylene fibers by the jelly-spinning-super-stretching technique is a novel spinning method that emerged in the late 1970s. The Dutch DSM company first applied for a patent in 1979, and then the industrialized production was realized by Allied Company of the United States, Toyobo-DSM Company established by Japan and the Netherlands, and Mitsui Company of Japan. The China Textile University Chemical Fiber Institute began research on the project in 1985, and gradually formed its own technology to produce high-performance ultra-high molecular weight polyethylene (UHMW-PE) fiber [3]. The ultrahigh molecular weight polyethylene (UHMW-PE) jelly spinning process is briefly described as follows: Dissolving ultra high molecular weight polyethylene (UHMW-PE) in a suitable solvent to make a semi-dilute solution, extruded through a spinning orifice, and then The spinning solution is quenched with air or water and solidified into frozen collagen filaments. In the frozen collagen filament, almost all of the solvent is contained therein, so the unwrapped state of the ultrahigh molecular weight polyethylene (UHMW-PE) macromolecular chain is well maintained, and the temperature of the solution is lowered, resulting in a super high in the jelly colloid. Formation of molecular weight polyethylene (UHMW-PE) folded chain crystals. In this way, by stretching the frozen collagen filaments by ultra-heating, the macromolecular chains can be sufficiently oriented and highly crystallized, thereby converting the macromolecules in the folded chain into the extended chains, thereby producing high-strength, high-modulus fibers. Ultra high molecular weight polyethylene (UHMW-PE) fiber is the third generation of special fiber in the world, with a strength of up to 30.8cN/dtex, the specific strength is the highest in chemical fiber, and it has good wear resistance, impact resistance and corrosion resistance. Excellent performance such as light resistance. It can be directly made into ropes, cables, fishing nets and various fabrics: bulletproof vests and clothing, cut-resistant gloves, etc., in which the bullet-proof effect of bullet-proof clothing is better than aramid. Ultra-high molecular weight polyethylene (UHMW-PE) fibers have been woven into ropes of different deniers in the world, replacing traditional steel cables and synthetic fiber ropes. The composite material of ultra high molecular weight polyethylene (UHMW-PE) fiber has been used as a shell for armored weapons, a protective cover for radar, helmets, etc. in military applications; bowstrings, sleds and water skis have been made on sporting goods.