The wear of non-metallic materials is mainly adhesive wear and abrasive wear. Adhesive wear is the transfer of material from one surface to another at the point of contact due to solid phase welding during relative motion.
Abrasive wear is surface abrasion or loss of surface material caused by microprotrusions on hard particles or harder materials.
In the field of engineering plastics, due to the generally poor thermal conductivity of polymer materials, the local heat generated during the friction process is relatively easy to reach the melting or softening point of engineering plastics, when the friction between the solids becomes and the resistance of the molten polymer to the solids on the opposite side of the friction sub, resulting in greater adhesive wear, which often appears as fish scale under the electron microscope.
With the addition of micronized PTFE powder or layer lubricant such as molybdenum disulfide, the friction force and friction heat will be reduced due to the reduction of friction coefficient, and the adhesive wear is controlled. When the amount of PTFE micronized powder added is relatively large, the transfer film between the friction surfaces becomes smoother and reflects better wear resistance, and the wear mode at this time is mainly abrasive wear formed by the solid on the polymer opposite to the friction substrate, which often shows a plow groove shape under electron microscopy.
For engineering plastics filled with glass fiber, the glass fiber will be crushed on the friction surface to form new abrasive grains, and the technical index of glass fiber and the amount of filling will have a greater impact on the wear resistance of engineering plastics.
The working conditions of wear-resistant engineering plastics are very important factors, such as temperature, load, friction speed, dry and wet conditions. Take PA6 as an example, the coefficient of friction is the largest at medium load, and the coefficient of friction is the largest at about 150 degrees.
At present, the domestic modified wear-resistant engineering plastics, mostly add molybdenum disulfide, its wear-resistant mechanism is to rely on its lamellar crystalline structure, can only produce black or gray products, and in the presence of water conditions, molybdenum disulfide due to water lubrication will be greatly reduced. The use of PTFE (polytetrafluoroethylene) micronized powder can solve such problems.
PTFE micro powder has a low molecular weight, the average molecular particle size of up to 1.5 microns, the appearance of white powder, with high molecular weight PTFE resin has all the excellent performance, its outstanding features are: particles into a spherical, no bonding between the particles, excellent dispersion, small particle size and uniform, large specific surface area, low bulk density, high oil absorption value, dispersion in the solvent low viscosity, can It can be uniformly mixed with other powder and liquid materials.
The use of PTFE micro powder can enhance the performance of the main material, such as.
1) Abrasion resistance, friction resistance and scratch resistance
2) Easy decontamination properties
3) Anti-adhesive properties
4) Lubricity properties (for engineering plastics modification)
5) Anti-friction and anti-wear properties
Micronized PTFE powder can improve some properties of the main materials (i.e. engineering plastics, general plastics, coatings, inks, lubricants, films, rubbers and lubricants), even in small amounts. This is because these micronized powders are resistant to harsh processing conditions and their properties remain virtually unchanged after they are incorporated into the host resin.
Adding a certain percentage of PTFE micronized powder can provide:
1. self-lubricating wear resistance
2. higher mold release performance
3. faster processing speed
For plastics, higher content is required when low friction, PV and wear resistance are required. And when used as a thickening agent in lubricants (such as grease), it is also necessary to use a higher content of micronized powder. PTFE filled blends are processed under the same conditions as the main material (such as plastic, rubber, etc.).
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