The methods to enhance the heat resistance of rubber sealing rings can be achieved from four core dimensions: material selection, formulation optimization, structural design, and process control. Specifically, they are as follows:
I. Material Selection: Select heat-resistant rubber based on temperature range
Fluorine rubber (FKM)
Thermal resistance range: Regular formulation can reach 230°C, special formulations (such as high fluorine content ≥ 66%) can exceed 250°C, and even short-term resistance to 300°C.
Advantages: Fluorine-carbon bond has high bond energy (489 kJ/mol), excellent heat resistance aging performance. For example, after continuous operation in a 200°C steam environment for 5,000 hours, the compression permanent deformation rate is only 12% (NBR, a nitrile rubber, reaches 38%).
Application scenarios: High-temperature and high-pressure sealing (such as oil refinery pumps and valves, automotive engine valve bodies).
Perfluoro rubber (FFKM)
Thermal resistance range: -25°C to 325°C, can withstand 350°C in extreme conditions for a short period.
Advantages: The hydrogen atoms in the molecular chain are completely replaced by fluorine atoms, with extremely strong chemical corrosion resistance and thermal stability, and a vacuum resistance of up to 1.33×10?? Pa.
Application scenarios: Semiconductor manufacturing, aerospace, petrochemicals, etc., in ultra-high temperature corrosive environments.
Silicone rubber (VMQ)
Thermal resistance range: -60°C to 250°C, can withstand 300°C for a short period.
Advantages: Excellent resistance to oxidation, weathering, and electrical insulation, good low-temperature elasticity.
Application scenarios: Wide temperature range sealing in electronic appliances, automotive ignition systems, etc.
Hydrogenated nitrile rubber (HNBR)
Thermal resistance range: Long-term use temperature up to 145°C, short-term resistance up to 160°C.
Advantages: After hydrogenation treatment of nitrile rubber, the saturation of the main chain increases, significantly enhancing heat resistance and chemical corrosion resistance.
Application scenarios: Medium-temperature sealing in automotive transmission systems, industrial hydraulic equipment, etc.
II. Formula Optimization: Improve heat resistance through component adjustment
Sulfurization system selection
Peroxide sulfurization: Forms carbon-carbon cross-links (C-C), with higher bond energy than sulfur cross-links (C-S), providing better heat resistance. For example, after peroxide sulfurization of fluorine rubber, the hardness fluctuation in 200°C reciprocating motion is <±3 Shore A, achieving zero leakage after 5,000 cycles.
Low sulfur high accelerator sulfurization: Reduces the generation of polysulfide bonds (S-S), reducing the risk of cross-linking bond breakage at high temperatures, suitable for general rubbers such as nitrile rubber.
Filler modification
Nano fillers: Adding 0.1% single-walled carbon nanotubes (SWCNT) can reduce the hardness fluctuation rate of fluorine rubber by 30%, increase the thermal conductivity by 40%, and increase the lifespan by 10 times in a 200°C plasma environment.
Low activated carbon black: Using thermally cracked carbon black, spray carbon black, or semi-reinforcing carbon black can reduce the heat generation and compression permanent deformation of the rubber compound, while reducing costs.
Plasticizer selection
High-temperature resistant plasticizers: Such as tridecyl esters (TOTM, TINTM), with low volatility and large molecular weight, can give hydrogenated nitrile rubber better heat resistance.
III. Structural Design: Match the requirements of the working conditions
Hardness matching
Low-pressure static sealing: Select 50±5 Shore A hardness, suitable for 5-10 MPa pressure.
Medium-pressure hydraulic system: Select 70±5 Shore A hardness, suitable for 15-20 MPa pressure.
Supercritical fluid equipment: Select 90±5 Shore A hardness, capable of withstanding 35-50 MPa pressure. For example, a vacuum coating machine uses an 80±5 hardness sealing component, with a 10-fold increase in lifespan in a high-temperature plasma environment.
Composite structure
Surface coating: Composite PTFE coating on fluorine rubber surface, through plasma treatment to form a 5-10 nm modified layer, increasing surface energy to 45 mN/m, and interface strength by 120%, suitable for chemical etching environments.
Multi-layer structure: Such as an outer layer of perfluoro rubber and an inner layer of fluorine rubber, which can balance heat resistance and cost.
IV. Process Control: Ensure production quality
Sulfurization process Low-temperature long-time vulcanization: For materials such as natural rubber (NR), vulcanization at a lower temperature (e.g. 140℃) for a longer period ensures the formation of a cross-linked network dominated by single sulfur bonds, thereby improving aging resistance.
Segmented vulcanization: For thick-walled O-rings, a segmented temperature rise vulcanization process is adopted to avoid insufficient vulcanization inside or excessive vulcanization outside.
Post-treatment processes
Heat treatment: After vulcanization, a secondary heat treatment (e.g. 170℃×2h) is carried out to eliminate internal stress and reduce compressive permanent deformation.
Surface treatment: Plasma treatment of silicone rubber can improve surface wettability and enhance the bonding strength with metals.
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