Ultra high molecular weight polyethylene
DATE：2022/7/15 9:12:46 / READ： / SOURCE：This station
Ultra high molecular weight polyethylene
Ultra high molecular weight polyethylene (UHMWPE) is a thermoplastic engineering plastic with linear structure. Its production method and molecular structure are basically similar to that of high-density polyethylene; It can be synthesized by low-pressure polymerization, slurry method and gas-phase method. The molecular weight control depends on changing the proportion of catalyst components, adding modifiers and adjusting process parameters. UHMWPE is the abbreviation of UHMWPE. Building formwork production line www.handern comUltra high molecular weight polyethylene is powder, with a density of 0936~0.964g/cm, non-toxic, not easy to absorb water, not easy to adhere, and no surface attraction; The mechanical and chemical properties are unique. It almost integrates the advantages of all kinds of plastics, and has the incomparable wear resistance, self lubrication and noise attenuation of ordinary polyethylene and other engineering plastics; Impact resistance, low temperature resistance and low temperature impact resistance; High temperature creep resistance, good thermal stability, melting point temperature of 190~210 ℃, thermal deformation temperature of 85 ℃ (at 046mpa), melt flow rate close to zero; Good cold resistance, embrittlement temperature lower than 140 ℃; Tensile strength up to 392mpa; Corrosion resistance and environmental cracking resistance are very good Building formwork production line www.handern com
UHMWPE performance item of Beijing No.2 auxiliary plant relative molecular weight /x10* 180~230:300 density / (g/cm) 0,93~0.945 powder apparent density / (g/cm) ³) 0.33~0.40 ash (mass) /% ≤ 0.15 moisture (mass) /% ≤ 0.15 tensile strength /mpa 30~40 fracture length ratio /% 300~400 impact strength (notch) /ckj/m) >150 melting humidity / ℃ 137 Vicat softening point / ℃ 132 embrittlement temperature / ℃ -70 volume resistivity /n · cm ≥ 10? Dielectric strength / (kv/mm) ≥ 35 relative dielectric constant <2.35 dielectric loss tangent <5x10 friction coefficient (ASTM d1894) 0.07~0.11 water absorption /% <0.01 wear rate /% 0.62 (better than PA6, PTFE, 45 carbon steel, stainless steel) building formwork production line www.handern com
HDPE performance comparison project ultra high molecular weight polyethylene ordinary high density polyethylene weight average molecular weight density / (g/cm) ³) 2x10 0.939 5x10 0.045 melting temperature / ℃ melt flow rate / (g/10min) 130~131 0.05 129~130 Rockwell hardness (HRC) 3835 deformation rate under load (50 ℃, 14MPa, 6h) /% 6.09.0 thermal deformation temperature (0.45MPa) / ℃ 79~83 63~71 Vicat softening point / ℃ 133 122 23 ℃ -40 ℃ environmental stress cracking (FSO) /h impact strength (notch) / (kJ / M) ²) 81.6100>400027.25.42000 building formwork production line www.handern com
See table 2-25 for the brand and performance of UHMWPE products produced by Beijing No. 2 auxiliary factory. See table 2-26 for the performance comparison between UHMWPE and ordinary HDPE. Within a certain temperature and concentration range, it can resist all kinds of corrosive media, chemicals (acids, bases, salts, except oxidizing acids) and cold resistance of organic solvents. Ultra high molecular weight polyethylene can be used at liquid helium temperature (-269 ℃). Because of its high molecular weight, extremely low melt flow rate, extremely high melt viscosity, extremely poor fluidity, and extremely sensitive to thermal shear, It is not suitable to use general thermoplastic molding equipment and process to shape products. Generally, it is formed by hot molding and cold pressing sintering. In recent years, due to the adoption of mwpe to achieve the purpose of improving the melting without reducing the molecular weight, the fluidity of the melt has been improved; Another point is to transform the equipment, adopt small compression ratio, large depth of thread groove, two screws of twin-screw extruder rotate in the same direction, slot the barrel at the feeding place, and adopt the forced feeding method to achieve the smooth transportation of raw materials at the beginning of the barrel; The extrusion process temperature is controlled within the range of 180~200 ℃, and the working speed of the screw is controlled within 10~15r/min to prevent the degradation of raw materials under high shear rate. Now, uhm WPE plates, bars, hollow products and films can be produced by this extrusion process. Building formwork production line www.handern com
When injection molding UHMWPE products with injection molding machine, the structure of the screw and molding die of the single screw injection molding machine should be properly improved; The technological conditions of plasticizing raw materials are also adjusted; If the molten material is sprayed under high pressure, its flow is conducive to mold filling, and the stability of the molding size of the product is ensured. Therefore, it should be noted that the injection pressure should be controlled above 12MP: the rotational speed of the screw plasticizing raw material should be controlled within the range of 40~60r/min, the rotational speed should be controlled within the range of 40~60r/min, and the material temperature is easy to rise. Such raw materials are also easy to degrade, resulting in a decrease in molecular weight, which will affect the performance of the product. UHMWPE is widely used in textile, packaging and transportation, machinery, chemical industry, mining, petroleum, agriculture, construction, electrical, food, medical treatment, sports and other fields because of its unique performance that other thermoplastics cannot compare and its moderate price. Such as corrosion-resistant tank lining, container and cooling tower body; Acid grinding shafts, shaft sleeves, eccentric wheels, gears, mixing blades, scraper blades in the paper industry, deflector hydrofoils; Wear resistant and cold resistant ice sports equipment, such as roller skate pulley, ski liner, crawler type ice and snow special auto parts, etc; Electroplating trough rollers for electrical insulation, insulators, insulation brackets, cable conduits, cable terminals, circuit breakers, etc. working in high-frequency and ultra-high-frequency intervals.
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