The main properties of fluororubber
(1) Corrosion resistance: Fluororubber has excellent corrosion resistance. Generally speaking, it is superior to other rubbers in terms of stability of organic liquids (fuel oil, solvent, hydraulic medium, etc.), concentrated acid (nitric acid, sulfuric acid, hydrochloric acid), high concentration of hydrogen peroxide and other strong oxidants. .
(2) Swell resistance: Fluororubber has high chemical stability and is the best medium resistance of all elastomers.
(3) Heat resistance and high temperature resistance: In the aspect of aging resistance, fluororubber can compete with silicone rubber and is superior to other rubbers. The change of properties of fluororubber at different temperatures is greater than that of silicone rubber and general-purpose butyl rubber. The tensile strength and hardness of the fluororubber are significantly decreased with the increase of temperature. The variation of tensile strength is: below 150 °C, with temperature It rises rapidly and decreases rapidly. Between 150 and 260 °C, it decreases slowly with increasing temperature.
The high temperature resistance of fluororubber is the same as that of silicone rubber, which is arguably the best in the current elastomer. 26-41 Fluorine rubber can be used for a long time at 250 °C, short-term use at 300 °C; 246 fluorine rubber heat resistance is better than 26-41. The properties of 26-41 after air heat aging at 300 °C × 100 h are equivalent to those of 246 after 300 °C × 100 h hot air aging. The elongation at break can be maintained at around 100% and the hardness is 90 to 95 degrees. . The Model 246 maintains good elasticity after hot air aging for 16 h at 350 °C. It maintains good elasticity after hot air aging for 110 min at 400 °C. After hot air aging for 110 min at 400 °C, it contains spray carbon black, thermal black or carbon fiber. The elongation of the rubber increases by about 1 /2 to 1 / 3, and the strength drops by about 1 / 2, and still maintains good elasticity. Type 23-11 fluoroelastomer can be used at 200 °C for a long time and at 250 °C for short-term use.
(4) Low temperature resistance: The low temperature performance of fluororubber is not good due to its own chemical structure. The low temperature resistance of fluororubber generally maintains the ultimate temperature limit of -15 to 20 °C. As the temperature decreases, its tensile strength becomes greater and it appears to be tough at low temperatures. When used as a seal, low temperature seal leakage problems often occur. The brittleness temperature varies with the thickness of the sample. For example, type 26 fluororubber has a brittle temperature of -45 °C at a thickness of 1.87 mm, -53 °C at a thickness of 0.63 mm, and -69 °C at a thickness of 0.25 mm. Its standard sample type 26 fluororubber has a brittleness temperature of -25 to -30 °C, the 246 type fluororubber has a brittleness temperature of -30 to -40 °C, and the type 23 fluororubber has a brittleness temperature of -45 to -60 °C.
(5) Resistance to superheated water and steam: The stability of fluororubber to hot water depends not only on the bulk material, but also on the compounding of the rubber compound. For fluororubbers, this property is primarily determined by its vulcanization system. The peroxide vulcanization system is better than the amine and bisphenol AF vulcanization system.
(6) Compression set performance: The compression deformation of fluororubber used for sealing at high temperatures is its key performance. The versatile application of the ventilated fluororubber is inseparable from the improvement of its compression set. It is an important property that must be controlled as a sealing article. The compression set is very large in the temperature range of 200 to 300 °C. However, in the 1970s, DuPont of the United States improved it and developed a low-compression permanent-setting compound (Viton E-60C), which was modified from the raw rubber variety (Viton A to Viton E-60) and vulcanized. The system selection (from the improvement of amine vulcanization to bisphenol AF vulcanization) is improved, which makes the fluororubber have better compression set when sealed at 200 °C for a long time. The fluororubber is stored at 149 °C for a long time. Its sealing retention rate is in a leading position in all types of rubber.
(7) Weathering resistance and ozone resistance: Fluororubber has excellent weather resistance and ozone resistance. It has been reported that the VitonA developed by DuPont still performs satisfactorily after 10 years of natural storage, and there is no significant cracking in the air with an ozone volume fraction of 0.01% for 45 days.
(8) Mechanical properties: Fluororubber generally has high tensile strength and hardness, but has poor elasticity.
(9) Electrical properties: The electrical insulation properties of fluororubber are not very good, and are only suitable for low frequency and low pressure.
(10) High vacuum resistance: Fluororubber has excellent vacuum resistance. This is because the fluororubber has a small gassing rate and a small amount of gas volatilization under high temperature and high vacuum conditions.
(11) Flame resistance: The flame resistance of rubber depends on the halogen content in the molecular structure. The more halogen content, the better the flame resistance. The fluororubber can be burned in contact with the flame, but is automatically extinguished after leaving the flame, so the fluororubber is a self-extinguishing rubber.
(12) Radiation resistance: Fluororubber is a material that is resistant to medium dose radiation. The radiation of high energy radiation can cause cracking and structuring of the fluororubber.