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Summary report of ultra high molecular weight polyethylene (UHMWPE) wear resistant materials

Jun 28, 2019

Ultra-high molecular weight polyethylene, the English name Ultra-High Molecular Weight Polyethylene (UHMWPE), is a linear structure of thermoplastic engineering plastic with excellent comprehensive properties. Its molecular structure is identical to that of ordinary polyethylene in the molecular backbone. A chain with (-CH2-CH2-) and a molecular weight of 106 or more. Because it has unique properties such as excellent wear resistance, self-lubricating and impact resistance compared to other engineering materials, it is widely used in general machinery, agricultural machinery, textile machinery, automobile, mining, paper, chemical, food industry. Wait for non-stick, wear-resistant, low noise and self-lubricating parts. In addition, it can also be used as special film, large container, large-shaped pipe and plate, etc., used for cargo loading and unloading chute, funnel, warehouse lining. 1. Basic properties of UHMWPE Ultrahigh molecular weight polyethylene generally refers to polyethylene with a relative molecular mass of more than 1 million. The relative molecular mass of ultrahigh molecular weight polyethylene produced in Germany has already reached more than 10 million. It has the following advantages: (1) Excellent wear resistance, mortar wear test shows that it is several times more wear-resistant than ordinary carbon steel and copper, and 4 times more wear resistant than nylon; (2) extremely high impact strength, than PA6 It is 10 times larger than PP; (3) It can absorb shock and noise; (4) It has very low friction coefficient, which is much smaller than nylon and other plastics, and can be lubricated; (5) It is not easy to adhere to foreign matter, and it is excellent when sliding. Anti-adhesive properties; (6) chemical resistance, disease can shield atomic radiation; (7) operating temperature range from -265 ° C to +100 ° C, low temperature to - 195 ° C, still maintain good toughness and strength (8) Non-toxic, non-polluting, recyclable and recyclable, with good thermal stability and non-absorbency compared with other plastics, can maintain dimensional accuracy without deformation; (9) low cost. Therefore, ultra-high molecular weight polyethylene is the best comprehensive engineering plastic in engineering plastics, which concentrates on the advantages of various plastics. In fact, there is currently no single polymer material with so many excellent properties. However, it also has shortcomings, mainly due to poor temperature resistance, low hardness, low tensile strength and poor flame retardancy. 2. Overview and current status of UHMWPE historical development The basic theory of ultra-high molecular weight polyethylene fiber was first proposed in the 1930s, followed by the emergence of gel spinning and plasticizing spinning to make ultra-high molecular weight polyethylene technically. A major breakthrough was made. UHMWPE was first developed by German scientist Dr. Ziegler in 1958. By the end of the 1960s, industrial production was realized abroad. Then in the 1970s, Capaccio and Ward of the University of Leeds in the UK first developed a molecular weight of 100,000. High molecular weight polyethylene fiber. China was successfully developed and put into industrial production in 1964. In 1975, the Netherlands invented the gel spinning method (Gelspinning) using decahydronaphthalene as a solvent, and successfully prepared UHMWPE fiber, and applied for a patent in 1979. After ten years of hard work, it was confirmed that the gel spinning method is an effective method for manufacturing high-strength polyethylene fibers, and has an industrialized future. In 1983, Japan used a gel extrusion super-stretching method to produce ultra-high molecular weight polyethylene fibers using paraffin as a solvent. The development of UHMWPE is very rapid. Before the 1980s, the world's average annual growth rate was 8.5%. After the 1980s, the growth rate was as high as 15% to 20%, while China's average annual growth rate was over 30%. In 1978, the world consumed 12,000 to 12,500 tons, and by 1990 the world demand was about 50,000 tons, of which the United States accounted for 70%. In 2007-2009, China gradually became the world's engineering plastics factory, and the development of the ultra-molecular weight polyethylene industry was very rapid. Among them, the ultra-high molecular weight polyethylene pipe was listed as the National Science and Technology Achievements Key Promotion Plan by the National Science and Technology (2000) No. 056 document of the Ministry of Science and Technology in 2001, and it belongs to new chemical materials and new products. The Ministry of Science and Technology of the State Planning Commission listed UHMWPE pipes as a priority project for high-tech industries. With the development of application fields and the continuous improvement of new technologies, the application range of ultra-high molecular weight polyethylene has been expanding and the demand has been increasing. At this stage, many high-end molecular weight polyethylene high-end products are used in military applications and high-tech fields, and a few companies mastering core technologies are strictly confidential in the preparation of ultra-high molecular weight polyethylene catalysts. There have been few reports on the preparation of polyethylene catalysts. In recent years, with the expansion of the use of ultra high molecular weight polyethylene for civilian use, the number of patents for ultrahigh molecular weight polyethylene catalysts has increased, but in general the number is still small. Foreign Hechst AG and Samsung Synthetic Chemical Co., Ltd. have applied for patents in China, basically using ultra-high molecular weight polyethylene products with improved conventional catalysts, utilizing changes in catalyst components and optimization of polymerization processes. Adjusting polymer properties Domestic ultra-high molecular weight polyethylene has developed rapidly in recent years, and the preparation technology of ultra-high molecular weight polyethylene catalyst has also been greatly developed. At present, most of the techniques reported in the literature are based on the improved Ziegler-Natta catalyst. It is worth mentioning that it is reported that Asahi Kasei Co., Ltd. has recently developed an ultra-high molecular weight polyethylene catalyst based on a metallocene catalyst and has begun to develop into the market. In recent years, UHMWPE's processing technology has also made a major breakthrough, from the initial sintering press molding to the special equipment extrusion molding, and the application field is also expanding. However, during the research, UHMWPE has some excellent properties that many other engineering plastics can't achieve, but it has some disadvantages, such as its low melt index (close to zero) and high melting point (190-210 °C). It has high viscosity and poor fluidity and is extremely difficult to process. Compared with other engineering plastics, it has low surface hardness and low heat distortion temperature, poor bending and creep properties, poor abrasion resistance and low strength. , affecting its use effect and application range. In order to overcome these shortcomings of UHMWPE, to make up for these shortcomings, and to apply them in some places with higher requirements, the current common method is to modify them. The commonly used modification methods are physical modification and chemical modification. , polymer filling modification, UHMWPE enhanced and improved. The modified day is to improve the melt flowability without affecting the main properties of UHMWPE, or to modify the defects of UHMWPE's own properties, such as improving melt flow, heat resistance, antistatic property, resistance Flammability and surface hardness, etc., enabling it to be processed on special equipment or general equipment