Silicone fluid is extremely stable against thermal oxidation. For example, the dimethyl silicone fluid DM-FLUID is virtually unchanged when exposed to temperatures up to 150°C in air. Methylphenyl silicone fluid exhibits even better heat resistance than dimethyl silicone fluid and can be used for long durations in environments reaching 250°C.
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Kinetic viscosity change of DM-FLUID-100cs and DM-FLUID-1,000csSilicone fluid has excellent low-temperature resistance. DM-FLUID remains fluid even at -50°C. Methylphenyl silicone fluid was specially developed for low-temperature applications, so it remains fluid even in environments of -65°C. Since temperature has little effect on viscosity, these products are ideal for applications in cold regions.
Silicone fluid shows little change in viscosity due to changes in temperature. It is thus ideal for use as instrument oil in instruments used in airplanes, automobiles, and trains, and for other applications that make use of silicone fluid's viscous properties. Low-viscosity (10 mm2/s and below) products aside, DM-FLUID offers the advantage of less temperature-dependent viscosity change than common mineral and synthetic oils or other silicone fluids.
The thermal conductivity of dimethyl silicone fluid is lower than that of common organic compounds (nearly the same as that of benzene and toluene) and is roughly 25% that of water. Although thermal conductivity increases with higher viscosities, it becomes nearly constant at viscosities above 100 mm2/s. The thermal conductivity of DM-FLUID is 2.4-3.5x10-4 cal/cm·sec·°C at viscosities below 20 mm2/s, and roughly 3.7-3.8x10-4 cal/cm·sec·°C at viscosities over 50 mm2/s.
The specific heat of silicone fluid varies somewhat depending on viscosity, but is generally about one-third that of water. The values are comparable to common organic compounds that have low specific heat. The specific heat of DM-FLUID is 0.39-0.47 cal/g·°C for viscosities below 20 mm2/s, and approximately 0.36 cal/g·°C at viscosities over 100 mm2/s.
Silicone fluid is nearly chemically inert and is virtually unaffected by 10% alkaline aqueous solutions or 30% acid aqueous solutions at ambient temperatures. However, viscosity increases and gelation can occur if even trace amounts of acids or alkalis are introduced at high temperatures. Silicone fluid is almost unaffected by the presence of aluminum, stainless steel, and most other metals. However, lead, selenium, and tellurium can cause gelation. Precautions must therefore be taken during handling.
Effects of DM-FLUID-50cs on metalsSilicone fluid has no adverse effect on metals, nor on most other substances. However, it may reduce the volume and weight of some rubber and plastic compounds due to extraction of the plasticizers when subjected to high temperatures. This tendency is especially strong for low-viscosity fluids. Particular care must be exercised when silicone fluid comes into contact with rubber sealing materials.
Effects of DM-FLUID-100cs on various plasticsThe surface tension of silicone fluid is much lower than that of water or common synthetic oils. Silicone fluids spread easily over the surfaces of various substances, and are thus widely used as release agents, defoamers, and ingredients for cosmetics.
Liquid Surface tension (mN/m) DM-FLUID 16 to 21 Mineral oil 29.7 Water 72The application of silicone fluid to mold surfaces prevents the adhesion of other materials, thereby enhancing mold releasability. Silicone fluids are widely used as release agents because they have excellent heat resistance and do not contaminate molds or molded materials.
Added in small amounts, silicone fluid has excellent defoaming action. Silicone fluid is primarily used as a defoamer for oil-based foaming fluids.
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Silicone fluid also has excellent water repellency. The degree of water repellency can be represented by water contact angle, which is over 90° for DM-FLUID. An excellent and durable water-repellent coating can be obtained by applying F-9W-9 or DM-FLUID to glass, ceramic, or fiber using a bake-on process. Silicone fluid can also be used to improve the fluidity of powders and prevent coagulation.
Water contact angleWater repellency mechanism of DM-FLUIDGenerally speaking, silicone fluid is physiologically inert and poses almost no risk to people or animals. Low-viscosity products excepted, DM-FLUID is nearly harmless unless ingested in large quantities. It is thus widely used as an ingredient in cosmetics.
Results of various safety testsSilicone fluid has extremely high shear resistance, and it resists shear degradation at high speeds and high loads, meaning it has a long operating life. When synthetic or mineral oils pass through narrow gaps under pressure, shear stress destroys the oil molecules, causing a drop in viscosity. In contrast, with dimethyl silicone fluid of viscosities below 1,000 mm2/s, there is almost no change in viscosity. However, with high-viscosity products there may be an apparent drop in viscosity depending on the shear velocity. Note that this is not due to destruction of the molecules, so the viscosity returns to the initial level when the shear stress is removed. The shear resistance of silicone fluids is over 20 times greater than that of even top-quality petroleum-based oils.
DM-FLUID: apparent kinetic viscosity and shear velocityUnlike mineral oil, silicone fluid exhibits extremely high compressibility and does not coagulate when pressurized. Silicone fluid has much higher compressibility than petroleum-based insulating oils or synthetic lubricants, and is thus well-suited for use as damper oil.
DM-FLUID: pressure and compressibility (25°C)Silicone fluid is highly soluble in hydrocarbon solvents such as toluene, xylene, ligroin, and mineral spirits as well as in chlorinated hydrocarbons. However, it is insoluble in ethanol, methanol, and water.
*KF-56 is soluble in ethanol.
Although silicone fluid has many advantageous properties (eg. stable viscosity, high- and low-temperature resistance) that make it ideal for use as a lubricant, its poor boundary lubrication properties on steel-steel interfaces limit its use as a lubricant for such applications. However, silicone fluid does provide good lubrication for steel-bronze, steel-aluminum, steel-zinc, and wood-wood interfaces and for various combinations of plastics.
Correlation between friction pressure and kinetic friction coefficient when silicone fluid (DM-FLUID-60,000cs) is added to various resinsIn terms of radiation resistance, methylphenyl silicone fluid is superior to dimethyl silicone fluid, and the stability of radiation resistance increases proportionately with the amount of phenyl groups present in the molecules. Due to this property and its resistance to high and low temperatures, methylphenyl silicone fluid is widely used in the high-temperature parts of radiological equipment.
Depending on processing requirements or usage, silicone fluids may be used as 100 % materials, in a diluted form &#; mostly in halogenated hydrocarbons, aromatic compounds or high-boiling white spirit &#; or in emulsified form usually as oil-in-water emulsions, mostly in low concentrations. Producers usually deliver these fluids in the following concentrations: from 10 to 50 % of silicone in solutions and from 20 to 60 % of silicone in emulsions.
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Read it Now!Silicone fluids are particularly used for special applications or applications requiring resistance to extreme weather conditions. Silicone fluids are chosen for such applications since they can adapt to extreme fluctuations in temperature (from -60 °C to 300 °C) and have high stability against all forms of radiation, in particular UV, to resist outdoor exposure. The extremely low volatility silicone fluids and resistance to weathering means that their waterproofing capacities are durable.