In PTFE products, filled PTFE products are the largest production, in foreign countries filled PTFE is generally completed by PTFE resin production plant, such as Germany Hoechst HosTaflonTF4000 series, HosTaflonTF3000 series and HosTaflon2000 series. In China, since PTFE resin production technology lags behind the processing technology, PTFE filling technology is done in the product processing plant. By adding different fillers such as inorganic, metal and polymer in PTFE resin to improve the pressure resistance, wear resistance, cold flow resistance, heat resistance, dimensional stability of PTFE. Filled products compared with pure PTFE, pressure resistance increased by 5 to 10 times, wear resistance increased by 1000 times, the coefficient of linear expansion reduced by 80%, thermal conductivity increased by 5 times, and reduce the volume resistance and surface resistance, mainly used in the mechanical industry for oil-free lubrication bearings, bearing bushings, piston rings, machine tool guides, etc. In recent years, foreign chemical anti-corrosion, filled with PTFE as a pipeline, valves, pumps, etc. The application of lining is developing rapidly, which is a new application area of filled PTFE.
According to these requirements commonly used fillers are: glass fiber, carbon fiber, graphite, quartz sand, molybdenum disulfide, amorphous carbon, calcium fluoride, bronze powder, ceramics, polyimide, polyphenylene, poly-p-hydroxyformate and so on.
Filled PTFE products are generally molded: the quality of filled PTFE products depends on the choice of resin filler, the design of the formula, the degree of homogeneity of material mixing and other factors. Currently there are three mixing methods used to fill PTFE: (1) dry mixing process requires a fast, uniform mixing device without dead space, applicable to the general requirements of the product. (2) solvent mixing, the solvent is acetone or methanol, for glass-filled PTFE.(3) wet mixing: the use of this process molding products with high mechanical strength, low wear, good corrosion resistance. The molding pressure of filled PTFE products depends on the volume ratio of filler in PTFE, such as: with 5% filler molding pressure of 250 bar; with 6% to 10% filler molding pressure of 350 bar; with 12% to 25% filler molding pressure of 500 bar; with more than 25% filler molding pressure of 700 bar. The sintering process for filled products is the same as for pure PTFE. But the filled products containing MoS2 require sintering in air medium at 360℃, or sintering in nitrogen medium at 380℃. Filled products containing glass fiber are suitable for sintering in nitrogen medium.
Post time: Feb-11-2022