Dimethicone and methylphenyl silicone fluids are widely used in hydraulic transmission systems and fluid connectors due to their wide viscosity range from 50 to 500 000 mm²/s. Compared with other liquids, silicone oil exhibits better heat resistance and oxidation resistance, as well as a wider range of temperature-viscosity characteristics. In order to maintain the stability of viscosity and torque under extreme high temperature conditions, such as 100°C to 200°C, and prevent gel formation, an appropriate amount of carbodiimide-containing compounds can be added to the silicone oil as a viscosity and torque stabilizing additive. Adapt to hydraulic transmission requirements under harsh working conditions.
Mechanism of action and effect evaluation of additives
The recommended dosage of additives is 0.1% to 3.0% of the silicone oil mass, and can be used together with other amine and phenolic antioxidants. The addition of carbodiimide-containing compounds can capture acidic substances that may be produced by silicone oil at high temperatures, thereby preventing silicon-oxygen bonds from being degraded by acid catalysis. This mechanism of action significantly improves the thermal stability of silicone oil.
Performance evaluation example
Taking dimethyl silicone oil with a viscosity of 10000 mm²/s as an example, it is modified by adding 2.0% N, N1-dicyclohexylcarbodiimide according to the mass fraction. The viscosity stability of the modified silicone oil was evaluated by the following method: first, the moisture mass fraction in the silicone oil was adjusted to 600 ppm, and then it was sealed in a pressure container. After heating at 170°C for 96 hours, measure the kinematic viscosity of the silicone oil and calculate the viscosity change rate. The low value of the viscosity change rate indicates that the silicone oil has better thermal stability. Under specific test conditions, silicone oil added with N,N1-dicyclohexylcarbodiimide showed a viscosity change rate of -0.3%, while silicone oil without this compound had a viscosity change rate of -6.9 under the same conditions. %, this comparison highlights the significant improvement effect of additives on the thermal stability of silicone oil.
2. Application of silicone oil in diffusion pump system
Tetramethyltetraphenyltrisiloxane and trimethylpentaphenyltrisiloxane are used as diffusion pump oils, which can achieve extremely high vacuum degrees of up to 10-9 to 10-8Pa. Thanks to the excellent heat resistance, thermal oxidation resistance and chemical stability of silicone oil, as well as its non-corrosive characteristics, silicone oil shows significant advantages in durability compared to traditional petroleum or fatty acid ester diffusion pump oils .
During the operation of the diffusion pump, even if the heater (450 watts) is not cut off after 15 minutes of operation, by using air to return to normal pressure and maintaining it for 1 minute, and then continuing to operate, such periodic operations will not affect the silicone oil. performance.
3. Application of heat carrier
Silicone oil has good thermal oxidation resistance, low vapor pressure and high flash point, and can be used as various high-temperature baths and high-temperature heat carriers.
Dimethyl silicone oil can be used stably for a long time in air below 175℃, while methylphenyl silicone oil can be used at high temperature of 200℃ for a long time, which makes them ideal choices for high temperature applications.
By adding specific heat-resistant additives to dimethyl silicone oil and methylphenyl silicone oil, the applicable temperature range of silicone oil can be further increased. Such modified silicone oil can be used as a heat carrier for rubber continuous vulcanization equipment, a heat carrier for plastic extruders, a heat carrier for petrochemical equipment, and a heat carrier for heat collection in solar systems, thereby expanding the industrial application of silicone oil. range of use.
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