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In July 2026, groundbreaking news emerged from the latest test site in China’s nuclear fusion energy sector: after nearly 8 years of targeted technical iteration and tens of thousands of extreme working condition simulation verifications, domestically produced modified methyl phenyl silicone oil has officially completed a 1200-hour continuous full-power plasma discharge condition loading test in the auxiliary thermal protection system of the divertor of a new-generation tokamak device. All core performance indicators have fully met the design requirements, and some key parameters are even more than 30% higher than similar international products. This breakthrough marks that the application boundary of methyl phenyl silicone oil has officially expanded from traditional industrial scenarios and computing power liquid cooling scenarios to the forefront of human energy technology, making it the world’s first organic silicon fluid material that has passed the full-cycle verification of the extreme working conditions of controlled nuclear fusion, completely breaking the nearly half-century technical monopoly of overseas special fluid materials in the core supporting field of nuclear fusion.
As a core category of special organosilicon fluids, the introduction ratio and distribution pattern of phenyl groups in the molecular structure of methyl phenyl silicone oil directly determine the extreme environment resistance of the material. Different from ordinary dimethyl silicone oil, the phenyl side groups of methyl phenyl silicone oil can form a special steric hindrance effect between the molecular chains of polysiloxane, greatly increasing the chemical bond energy of the main molecular chain, and enabling the material to achieve order-of-magnitude improvements in thermal oxidative stability, high-energy particle radiation resistance, and wide-temperature-range viscosity stability. Previously, methyl phenyl silicone oil products worldwide could only cover the conventional working condition range of -70°C to 250°C. However, in the peripheral area of the divertor of a controlled nuclear fusion device, it is not only necessary to face local thermal shocks exceeding 350°C at maximum, but also to continuously withstand long-term radiation from high-energy neutrons, gamma rays and hydrogen isotope particles escaping from the plasma. At the same time, the working medium inside the system has to circulate and switch repeatedly between the standby low temperature of -60°C and the continuous high temperature of 320°C. Under such extreme composite working conditions, traditional fluid materials often experience molecular chain breakage, sharp performance degradation or even carbonization failure in less than 100 hours, which completely cannot meet the core requirement of long-pulse continuous operation of nuclear fusion devices.
In order to overcome this world-class material problem, domestic scientific research teams, joining forces with multiple research forces in the nuclear industry and organosilicon material fields, have carried out disruptive innovation starting from the source of molecular structure design: abandoning the traditional random copolymerization process commonly used in the production of methyl phenyl silicone oil, they adopted the "fixed-point phenyl embedding" controllable synthesis technology for the first time, which accurately distributes phenyl groups at preset sites on the main chain of the polysiloxane molecule. This allows each phenyl group to exert the maximum radiation protection effect in the molecular chain, while avoiding the long-standing industry pain points of traditional random copolymerization processes, such as easy occurrence of phenyl agglomeration and uneven local molecular chain rigidity. On this basis, the research team also adopted a special metal ion complexation removal process to control the content of trace transition metal impurities in the fluid below 1ppb, completely eliminating the risk of catalytic degradation of molecular chains caused by metal impurities in high-temperature radiation environments. The final modified methyl phenyl silicone oil dedicated to nuclear fusion, verified by a third-party authoritative testing agency, has a maximum long-term continuous operating temperature of 380°C. Under a cumulative gamma ray radiation dose of 2000krad, the viscosity change rate is less than 3.2%, and it can still maintain good fluidity at an ultra-low temperature of -85°C without solidification or crystallization. All performance indicators have refreshed the public records of global methyl phenyl silicone oil products.
During the actual loading test of this tokamak device, this modified methyl phenyl silicone oil, as the core heat transfer and damping medium of the divertor auxiliary thermal protection circuit, experienced 1200 hours of continuous discharge operation throughout the whole process, and withstood more than 400 long-pulse plasma shocks in total. The medium temperature inside the system completed hundreds of cycles of switching between -55°C and 310°C. The sampling analysis results after the test show that the overall thermal weight loss rate of the medium is less than 0.12%, the acid value increase is less than 0.02mgKOH/g, and its compatibility with all contact materials such as tungsten-copper alloy, 316L stainless steel and silicon carbide coating in the circuit reaches 100%, without any signs of corrosion, coking or performance degradation. Nuclear engineering experts participating in the test said that the successful application of this methyl phenyl silicone oil solves the long-standing material bottleneck of the auxiliary thermal protection system that restricts the long-pulse continuous operation of tokamak devices, raising the expected continuous operation time of the divertor of the new-generation nuclear fusion experimental reactor from the original hundreds of hours to the level of tens of thousands of hours, providing key material support for the commercialization process of controlled nuclear fusion energy in China.
In addition to the major breakthrough in the field of controlled nuclear fusion, methyl phenyl silicone oil has recently achieved large-scale implementation in high-end scenarios of multiple national strategic emerging industries. In the lunar rover movement system of the new-generation deep space exploration mission, low-volatility modified methyl phenyl silicone oil is used as the long-term lubricating medium for wheel bearings. It has passed the ultra-wide temperature range environment simulation test from -196°C to 120°C on the lunar surface, and its lubrication life reaches more than 15 years under the working conditions of high vacuum and intense cosmic ray radiation, fully meeting the mission requirements of long-term lunar resident exploration. In the field of offshore wind power, high-phenyl-content methyl phenyl silicone oil is used as the damping medium for the pitch system of offshore wind turbines. The measured data of continuous operation for 5 years in the harsh coastal environment with high salt spray and strong ultraviolet rays shows that the performance degradation rate of the medium is less than 2%, completely solving the industry problem that traditional hydraulic oil is prone to aging leakage and high maintenance cost in offshore wind power scenarios. At present, more than 30,000 offshore wind turbines in China have completed the replacement and upgrading of this type of medium. In the field of rail transit, modified methyl phenyl silicone oil is used as the buffer damping medium for the doors of high-speed EMUs. It can still maintain stable buffer performance at -40°C in the extremely cold regions of Northeast China, reducing the impact vibration amplitude of door opening and closing by 60%, greatly improving the comfort and reliability of high-speed rail operation in extremely cold regions.
The latest "White Paper on the Development of the Global Methyl Phenyl Silicone Oil Industry" released by authoritative industry institutions shows that the total market size of global methyl phenyl silicone oil has exceeded 28 billion US dollars in 2026, of which Chinese enterprises contribute more than 60% of the technology, and more than 75% of the new production capacity of global high-end special methyl phenyl silicone oil is concentrated in China. With the continuous explosion of high-end downstream scenarios such as nuclear fusion, deep space exploration, computing power liquid cooling and new energy, it is expected that the global market size of methyl phenyl silicone oil will exceed 70 billion US dollars by 2030, becoming one of the core key materials supporting the development of global high-end manufacturing and cutting-edge energy technology. Industry experts pointed out that the technological breakthrough process of methyl phenyl silicone oil is a typical epitome of China’s special organosilicon industry from following to leading. In the future, with the continuous iterative upgrading of the entire industrial chain technology, China will establish complete technological and industrial advantages in the global high-end organosilicon material sector, providing solid material support for the progress of global industrial technology.
