However, pure PTFE is not wear-resistant, and in poor mechanical properties, easy creep, adding a certain amount of filler in PTFE products can improve the wear resistance of PTFE, thermal conductivity, creep resistance, self-lubrication and other aspects. Compared with pure PTFE, the filled PTFE product's pressure resistance is increased 5-10 times, wear resistance is increased 1000 times, linear expansion coefficient is reduced 80%, thermal conductivity is increased 5 times, volume resistance and surface resistance are reduced.
Kintowe filled PTFE products are mainly used in mechanical industry, such as oil-free bearings, bearing pads, piston rings, machine tool guides and so on.
Common fillers include carbon fiber, glass fiber, bronze powder, graphite, molybdenum disulfide (MoS2) and some polymer fillers.
1) Carbon fiber. The mechanical properties, heat resistance and friction resistance of ptfe can be improved by carbon fiber. The linear expansion coefficient of PTFE filled with carbon fiber is small, the thermal conductivity is high, and the compressive strength, creep resistance and wear resistance in water are greatly improved.
(2) Glass fiber. Generally filled to ptfe glass fiber diameter of 10 ~ 13μm, the average length of 80μm, length-diameter ratio of 5 ~ 10, the filling amount is generally 15% ~ 25%. Add glass fiber, will make its creep resistance and cold flow resistance get more significant improvement, wear resistance will be greatly improved. However, with the increase of glass fiber content, its tensile strength, elongation and toughness will gradually decrease. The coefficient of friction increases gradually.
(3) Graphite. Graphite can be divided into polar graphite, nuclear graphite and oil graphite three. The first two kinds of PTFE filling are more effective, its dosage is generally 15% ~ 30%. Graphite filled PTFE has good dimensional stability, good chemical resistance, compressive creep and good thermal conductivity.
(4) Bronze powder. The amount of PTFE filled with bronze powder alone is about 60%, and it can also be mixed with carbon fiber, glass fiber and lead oxide. Before filling, the bronze powder shall be oxidized to reduce the risk of thermal decomposition and fire. The addition of bronze powder improves its creep resistance, pressure resistance and heat dissipation, especially for the occasion of friction heat.
(5) Molybdenum disulfide (MoS2). The filling amount of MoS2 is small, generally used with other fillers, its content is generally 5%. The addition of molybdenum disulfide can improve the rigidity and hardness of PTFE, reduce friction coefficient and wear, improve creep resistance and electrical insulation, adding a large number of molybdenum disulfide can improve the thermal conductivity of PTFE.
