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UHMWPE has excellent wear resistance, good low temperature impact resistance, self-lubrication, non-toxic, water resistance, chemical resistance, heat resistance is better than general PE, the disadvantage is low heat resistance (heat deformation temperature), The processability is poor, the hardness, rigidity and creep resistance of the outer surface are not as good as those of general engineering plastics, and the expansion coefficient is too large. UHMWPE has poor fluidity and extremely high viscosity in the molten state. It is a rubber-like high-viscosity elastomer. In the early days, it could only be formed by pressing and sintering methods, and it could also be processed by extrusion, injection molding and blow molding.
Features：
1. Improve wear resistance. One of the most striking properties of EMW polyethylene is its extremely high abrasion resistance, which is invaluable in many engineering applications. Among all plastics, its wear resistance is the best, and even the regular wear resistance of many metal materials (such as carbon steel, stainless steel, bronze, etc.) is not as good as it. As the molecular weight of polyethylene increases, the material becomes more wear-resistant.
2. Extremely high impact resistance. The impact strength of ultra-high molecular weight polyethylene is related to its molecular weight. When the molecular weight is lower than 2 million, the impact strength increases with the increase of the molecular weight, and reaches a peak at about 2 million. After the peak, the impact strength increases with the molecular weight. will decline. This is because the molecular chain is abnormal and hinders its photocrystallization, so that there is a large amorphous region in the macromolecule, which can absorb a large impact energy.
According to the literature, the impact strength values of UHMWPE and other plastics measured by the ASTM-D256 method can be drawn from the comparison: the room temperature impact resistance of UHMWPE can be divided into polycarbonate, which is known for its impact resistance. Comparable to commonly used engineering plastics. Ultra-high molecular weight polyethylene still has strong impact resistance even at a low temperature of -40 °C, and even at a liquid gas temperature of -269 °C, it can still maintain good impact resistance. The application of ultra-high molecular weight polyethylene extends to the field of cryogenic engineering.
3. Low friction coefficient. UHMWPE is very wear-resistant, has a low coefficient of friction and good self-lubrication, and is an ideal material for bearing bushings, sliders and linings.
The use of ultra-high molecular weight polyethylene as the friction part of the equipment can not only improve the wear-resistant life, but also save energy.
4. Good chemical resistance. Ultra-high molecular weight polyethylene has good chemical corrosion resistance. Except for concentrated nitric acid and concentrated sulfuric acid, it will not be corroded in all lye and acid solutions, and can be used in concentrated hydrochloric acid at a temperature (80°C, It is also stable in <20% nitric acid, <75% sulfuric acid, and it is also stable in water, liquid washing.)
However, ultra-high molecular weight polyethylene is very easy to swell in aromatic or halogenated compounds (especially under higher temperature conditions), so special attention should be paid during application.
5. Very low water absorption. UHMWPE has a very low water absorption rate, it is almost non-absorbent, does not swell in water, and is much less absorbent than nylon.
6. Thermal properties. According to the method of ASTM (load 4.6kg/cm2), the heat distortion temperature is 85℃. Under a small load, the service temperature can reach 90℃. In special cases, it is allowed to use at a higher temperature. High molecular weight polyethylene is a material with excellent toughness, so its low resistance is also very good, and it still has a certain degree of ductility at a low temperature of -269 ° C, and there is no sign of embrittlement.
7. Electrical properties. UHMWPE has excellent electrical properties in a wide temperature range, its volume resistance is 10-18CM, its breakdown voltage is 50KV/mm, and its dielectric constant is 2.3. In a wide temperature and frequency range, its electrical properties change very little. In the heat-resistant temperature range, it is very suitable for use as structural materials in electrical engineering and materials in paper mills.
8. Non-toxic ultra-high molecular weight polyethylene is tasteless, non-toxic, odorless, non-corrosive, and has physiological circulation and physiological adaptability. The United States Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA) allow it to be used in contact with food and medicines.
UHMWPE has excellent wear resistance, good low temperature impact resistance, self-lubrication, non-toxic, water resistance, chemical resistance, heat resistance is better than general PE, the disadvantage is low heat resistance (heat deformation temperature), The processability is poor, the hardness, rigidity and creep resistance of the outer surface are not as good as those of general engineering plastics, and the expansion coefficient is too large. UHMWPE has poor fluidity and extremely high viscosity in the molten state. It is a rubber-like high-viscosity elastomer. In the early days, it could only be formed by pressing and sintering methods, and it could also be processed by extrusion, injection molding and blow molding.
Features：
1. Improve wear resistance. One of the most striking properties of EMW polyethylene is its extremely high abrasion resistance, which is invaluable in many engineering applications. Among all plastics, its wear resistance is the best, and even the regular wear resistance of many metal materials (such as carbon steel, stainless steel, bronze, etc.) is not as good as it. As the molecular weight of polyethylene increases, the material becomes more wear-resistant.
2. Extremely high impact resistance. The impact strength of ultra-high molecular weight polyethylene is related to its molecular weight. When the molecular weight is lower than 2 million, the impact strength increases with the increase of the molecular weight, and reaches a peak at about 2 million. After the peak, the impact strength increases with the molecular weight. will decline. This is because the molecular chain is abnormal and hinders its photocrystallization, so that there is a large amorphous region in the macromolecule, which can absorb a large impact energy.
According to the literature, the impact strength values of UHMWPE and other plastics measured by the ASTM-D256 method can be drawn from the comparison: the room temperature impact resistance of UHMWPE can be divided into polycarbonate, which is known for its impact resistance. Comparable to commonly used engineering plastics. Ultra-high molecular weight polyethylene still has strong impact resistance even at a low temperature of -40 °C, and even at a liquid gas temperature of -269 °C, it can still maintain good impact resistance. The application of ultra-high molecular weight polyethylene extends to the field of cryogenic engineering.
3. Low friction coefficient. UHMWPE is very wear-resistant, has a low coefficient of friction and good self-lubrication, and is an ideal material for bearing bushings, sliders and linings.
The use of ultra-high molecular weight polyethylene as the friction part of the equipment can not only improve the wear-resistant life, but also save energy.
4. Good chemical resistance. Ultra-high molecular weight polyethylene has good chemical corrosion resistance. Except for concentrated nitric acid and concentrated sulfuric acid, it will not be corroded in all lye and acid solutions, and can be used in concentrated hydrochloric acid at a temperature (80°C, It is also stable in <20% nitric acid, <75% sulfuric acid, and it is also stable in water, liquid washing.)
However, ultra-high molecular weight polyethylene is very easy to swell in aromatic or halogenated compounds (especially under higher temperature conditions), so special attention should be paid during application.
5. Very low water absorption. UHMWPE has a very low water absorption rate, it is almost non-absorbent, does not swell in water, and is much less absorbent than nylon.
6. Thermal properties. According to the method of ASTM (load 4.6kg/cm2), the heat distortion temperature is 85℃. Under a small load, the service temperature can reach 90℃. In special cases, it is allowed to use at a higher temperature. High molecular weight polyethylene is a material with excellent toughness, so its low resistance is also very good, and it still has a certain degree of ductility at a low temperature of -269 ° C, and there is no sign of embrittlement.
7. Electrical properties. UHMWPE has excellent electrical properties in a wide temperature range, its volume resistance is 10-18CM, its breakdown voltage is 50KV/mm, and its dielectric constant is 2.3. In a wide temperature and frequency range, its electrical properties change very little. In the heat-resistant temperature range, it is very suitable for use as structural materials in electrical engineering and materials in paper mills.
8. Non-toxic ultra-high molecular weight polyethylene is tasteless, non-toxic, odorless, non-corrosive, and has physiological circulation and physiological adaptability. The United States Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA) allow it to be used in contact with food and medicines.
