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Wear resistance and friction coefficient of polyurethane

Views: 297 Update date: May 06,2020

Wear resistance and friction coefficient of polyurethaneThe wear resistance and friction coefficient of polyurethane elastomer are outstanding. Its wear value is generally in the range of 0.03-0.20m m 3/m (Akron wear), which is much smaller than other polymer materials, 3-8 times better than natural rubber, and the actual use effect is often better. The wear resistance of polyurethane elastomer is determined by its molecular structure and aggregate structure, which is manifested in the high tear strength, modulus of elasticity, tensile strength, elongation at break and elasticity of polyurethane elastomer, while the wear resistance can generally be regarded as the measurement of mechanical properties such as tear strength of materials. Polyurethane elastomer has self-lubricating effect, which may be related to the lubricating effect of the fine powder it abrades. The ground surface is not easy to be hairy, and the more it is grinded, the smoother it is, showing excellent wear-resistant effect. However, the wear resistance of polyurethane elastomer is seriously affected by the surface heat. The surface heat generation is related to the friction coefficient of polyurethane elastomer, the relative moving speed of two friction surfaces, the applied external force and whether the friction surface is dry or wet. The friction coefficient of polyurethane elastomer is not low, generally above 0.5, but it can be adjusted as wide as the hardness, as low as 0.2, as high as 2-3, which mainly changes with the hardness. The higher the hardness is, the smaller the friction coefficient is. The lower the hardness is, the larger the friction coefficient is. This is related to the softer the material and the larger the contact surface. The friction coefficient increases with the increase of the surface temperature, and reaches the maximum value at about 60 , and then changes little or decreases.

The friction coefficient (μ) is the ratio of the friction between the surfaces (f) and the vertical force (n) acting on one of the surfaces. The static friction coefficient is large, and the dynamic friction coefficient is also large, and the former is larger than the latter, indicating that to make the object move in the plane, the starting force is larger than the force to keep moving. There are many such examples in daily life, which are not difficult to understand. Friction coefficient is "a double-edged sword". Some applications need a small coefficient of friction, some applications need a large coefficient of friction. For example, the friction coefficient of the rubber fender used in the ship terminal is required to be small (such as 0.2) to reduce wear. There are transmission gear, sieve plate, hydrocyclone, scraper, scraper and other products are required to have small friction coefficient. But the friction drive rubber wheel requires a larger friction coefficient to drive the passive wheel to rotate. Also, the friction coefficient of automobile tires should not be small, generally 0.7-1.0. In particular, the wet friction coefficient is small, and the tire is easy to slip. In case of emergency, the car can not be braked, which will bring security risks. In practical application, people will not only make use of the advantages of large friction coefficient, but also find ways to reduce the friction coefficient in applications requiring low friction coefficient, and try to avoid or reduce the harm of sliding friction. For example, rolling friction drive and gear drive are the best examples to overcome sliding friction. In addition, in addition to improving the hardness and reducing the friction coefficient, lubricant, graphite, molybdenum disulfide and tetrafluoroethylene powder can also be added to further reduce the friction coefficient of the material and reduce the internal heat, so as to achieve the best use effect.

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