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In the third quarter of 2026, the domestic special silicone material sector achieved another major industrial breakthrough: a continuous production unit for full-spectrum ethyl silicone oil with a designed annual capacity of 32,000 tons officially completed a 168-hour full-load steady-state operation assessment and was put into mass production and delivery. For the series of ethyl silicone oil products produced by this unit, the kinematic viscosity covers the full range from 5mm²/s to 10000mm²/s. Among them, the pour point of the low-viscosity low-temperature resistant grade is as low as -90°C, the total volatile content after constant-temperature baking at 200°C for 24 hours is less than 0.05%, and the electric breakdown strength is greater than 45kV/mm. All core performance indicators have reached the international leading level. This achievement marks that China has completely broken the nearly 40-year technological monopoly of overseas enterprises on high-grade ethyl silicone oil, providing fully independent and controllable core basic material support for key national fields such as special lubrication for polar equipment, deep-cooling industrial fluid sealing, and ultra-high voltage power insulation.
Ethyl silicone oil is a type of special modified silicone oil formed by homopolymerization or copolymerization of polydiethylsiloxane. As the category with the most prominent low-temperature resistance in the organic silicone material system, it completely changes the low-temperature movement characteristics of the molecular chain of traditional methyl silicone oil by replacing all or part of the methyl groups on the side chain of the polysiloxane with ethyl groups. Compared with ordinary methyl silicone oil, ethyl silicone oil has lower surface tension, more gentle viscosity-temperature characteristics, and a greatly widened low-temperature resistance range. At the same time, it has excellent electrical insulation, chemical stability and radiation resistance, making it an irreplaceable special basic raw material for other silicone materials. In the extreme low-temperature environment below -70°C, ordinary methyl silicone oil will quickly solidify and lose fluidity, and mineral-based lubricants have long been completely hardened, while high-quality ethyl silicone oil can still maintain stable lubrication and sealing performance. This unique property makes it a core supporting material for polar scientific research equipment, aerospace deep-cooling components, LNG industrial supporting equipment, and power facilities in alpine regions.
For nearly 40 years, the domestic ethyl silicone oil industry has long stayed in the primary development stage of low added value and low purity, and has been unable to break through three common industry technical bottlenecks. The first is the problem of monomer copolymerization uniformity: the hydrolysis reaction activity of ethyl chlorosilane and methyl chlorosilane varies greatly. Under the traditional intermittent hydrolysis equilibrium process, the problem of uneven distribution of molecular chain segments is very likely to occur. A large number of random block structures with local ethyl enrichment or missing directly lead to a significant deterioration in the low-temperature fluidity of the product. The pour point of ethyl silicone oil produced by domestic traditional processes is generally higher than -55°C, which completely cannot meet the usage requirements of extreme environments below -70°C. The second is the problem of deep removal of high-boiling substances: a large number of high-boiling ethyl-substituted small-molecule cyclic siloxanes will be generated during the synthesis of ethyl silicone oil. The boiling points of these impurities are much higher than that of ordinary methyl cyclosiloxanes, and conventional vacuum distillation processes cannot achieve deep removal. The total volatile content of domestic traditional products at 200°C for 24 hours is generally higher than 2.1%. Under high-temperature service environments, the continuous precipitation of small molecules will easily cause pipeline blockage, sealing failure or insulation performance degradation of precision equipment. The third is the problem of precise regulation of full-viscosity spectrum products: the reaction process of the traditional intermittent process has poor controllability, and the viscosity deviation of products from different batches has long been higher than 12%, making it impossible to achieve stable mass production of all products in the full range from low viscosity to high viscosity. 100% of the high-end special viscosity grades are dependent on imports. Previously, more than 95% of the market share of high-quality ethyl silicone oil used in domestic high-end fields was monopolized by leading overseas enterprises. The procurement price of controlled special grades in polar equipment, nuclear industry and other fields is 12 to 18 times that of ordinary methyl silicone oil, and the delivery cycle of some customized special specifications can be as long as 30 months, which has seriously restricted the iterative upgrading speed of China's high-end equipment industries related to alpine and deep-cooling environments.
The new continuous production process system that has achieved full production this time has corely overcome three technical barriers that have plagued the global ethyl silicone oil industry for nearly half a century. First, a phase-transfer catalyzed gradient hydrolysis copolymerization technology was pioneered. The R&D team abandoned the traditional idea of directly mixing ethyl chlorosilane and methyl chlorosilane into the reaction kettle, and independently developed a new supported phase-transfer composite catalyst. In 27 series-connected plug flow reaction units, according to the difference in monomer activity of different reaction sections, the contact ratio and reaction temperature of the water phase and oil phase are dynamically adjusted, so that ethyl groups achieve nearly perfect uniform random distribution on the polysiloxane molecular chain. From the source of polymerization, the proportion of random block structures is controlled below 0.15%, and the pour point of the final product is directly reduced to -90°C, setting a new global record for the low-temperature resistance of ethyl silicone oil. Second, the world's first 12-stage coupled purification system for ethyl silicone oil systems has been built. Aiming at the industry pain point that ethyl-substituted small-molecule cyclic siloxanes have high boiling points and extremely low relative volatility with the target product, the team innovatively adopted a combined purification process of "6-stage ultra-high vacuum distillation + 5-stage molecular distillation deep devolatilization + supercritical inert fluid extraction and replacement". The operating temperature throughout the process is strictly controlled below 195°C, which completely avoids the oxidative decomposition of ethyl groups at high temperatures. The total residual amount of ethyl-substituted rings in the final product is less than 5ppm, and the total volatile content after constant-temperature baking at 200°C for 24 hours is only 0.042%, far lower than the average level of 2.1% of traditional process products, fully meeting the low-precipitation requirements of polar equipment for long-term service of more than 10 years. Third, a full-process in-situ real-time closed-loop quality control system has been built. The entire production unit, covering monomer pretreatment, hydrolysis copolymerization, purification and separation, and finished product blending, is equipped with online nuclear magnetic resonance and online gel permeation chromatography detection modules. The system samples and analyzes the molar proportion of ethyl groups, molecular chain distribution, and ring residual amount of the reaction system in real time every 2.5 seconds. Once the parameters have a tiny deviation at the 0.02% level, the system automatically completes dynamic parameter adjustment, completely eliminating the performance difference between products from different batches in the traditional intermittent process, realizing that the viscosity deviation of products from different batches across 62 months is less than 0.8% with zero performance drift, and can stably produce all grades of products in the full viscosity range from 5mm²/s to 10000mm²/s.
At present, this independently developed full-spectrum high-quality ethyl silicone oil has completed long-term industrial application verification for more than 58 months in multiple national strategic core fields. In the field of polar scientific research, the polar vehicle wheel axle lubricating grease prepared with this product can still maintain stable lubrication performance in the extreme low-temperature environment of -85°C, and no obvious performance degradation after 12 months of polar field operation test. Related products have been batch applied in the full-system lubrication supporting of China's new-generation polar scientific research vehicles. In the LNG industry, the deep-cooling sealing liquid prepared with this product as the basic raw material can still maintain stable sealing performance at the low temperature of -196°C, without solidification or crystal precipitation. It has been fully applied in the core pump valve sealing system of large LNG receiving stations. In the field of ultra-high voltage power, the product has a volume resistivity greater than 2.5×10¹⁵Ω·cm and a breakdown voltage greater than 48kV/mm. The insulation performance does not decrease significantly in the alpine environment of -60°C, and its related performance fully meets the usage requirements of insulating oil for UHV transmission lines in the alpine regions of western China. In the nuclear industry, after being irradiated by a cumulative γ-ray dose of 12Mrad, the product still maintains a flowing state without gelation or obvious viscosity rise, fully meeting the usage requirements of special protective fluid in the core loop of nuclear reactors. In the field of special rubber processing, the rubber release agent prepared with this product as the core has a surface tension as low as 15.8mN/m, and can still maintain stable film-forming performance at a high temperature of 180°C. The demolded rubber products have no oil marks or precipitates on the surface, and have been widely used in the large-scale production of high-end special rubber seals.
According to the latest industry operation monitoring data, the market demand for domestic high-quality ethyl silicone oil in 2026 increased by 372% year-on-year compared with the same period in 2025. With the official launch of this domestic continuous production line, the market pattern where overseas products have long monopolized the market has been completely broken. The market procurement price of high-end ethyl silicone oil has dropped by 79% year-on-year, and the delivery cycle for core downstream users has been greatly shortened from the original 30 months to less than 5 days. With the subsequent start of construction of the second production line of the same scale, it is expected that by 2031, the global market share of domestically produced high-quality ethyl silicone oil will exceed 91%. It will not only fully meet the upgrading needs of domestic downstream industries such as polar equipment, LNG industry and UHV power transmission, but also greatly enhance the core voice of China's basic organosilicon high-end special intermediates in the global new material industrial chain, providing key material support for the development of global deep-cooling and alpine-related industries.
