Rubber sealing rings are vital components in numerous industrial manufacturing fields. Their high-temperature resistance directly determines whether equipment suffers liquid or gas leakage, or even shutdown failures. It is crucial to select suitable rubber sealing rings in advance, rather than trying to fix problems after malfunctions occur. Technically, high temperature resistance is closely linked to the thermal stability of rubber molecular chains. For instance, the carbon-fluorine bond energy of fluororubber reaches 485 kJ/mol, significantly higher than the carbon-hydrogen bond energy of common rubber, which is around 410 kJ/mol. The silicon-oxygen bond energy of silicone rubber stands at approximately 443kJ/mol, surpassing that of ordinary organic polymers (about 346kJ/mol). Accordingly, they boast excellent heat resistance and will not decompose or melt under high temperatures.   PART 01 High-temperature Resistance Comparison of Sealing Ring Materials FKM Usable temperature range -20℃ to 200℃. Withstands 250℃ briefly and 300℃ momentarily. Features oil, acid, alkali, and aging resistance. Ideal for engines, chemical facilities, fuel systems, and high-temperature valves. VMQ Wide temperature tolerance, long-term service at -60℃ to 200℃. Excellent cold and heat resistance. Special formulas endure over 250℃ temporarily. Suitable for home appliances, medical, and electronic applications. FVMQ Outstanding heat resistance. Stable from -50℃ to 250℃. High-grade variants sustain peak temperature up to 300℃ instantly. EPDM Good heat resistance, temperature range -55℃ to 150℃. Excellent resistance to steam and hot water, widely used in heating pipelines and cooling systems. NBR Working temperature -20℃ to 100℃, maintains stable sealing performance within the range. Rapid aging occurs above 120℃, which is not applicable for continuous high-temperature service. PTFE & Flexible Graphite Non-traditional rubber materials with superior extreme high-temperature performance. Filled PTFE dynamic seal withstands up to 265℃. Metal-clad flexible graphite static seal resists temperature up to 650℃. Applied to ultra-high temperature static sealing in oil refining and high-temperature furnaces.   PART 02 High-temperature Application of Sealing Rings Rubber materials retain elasticity, sealing performance, and mechanical strength within specific temperature ranges, enabling long-term service. Certain types can endure short-term high temperatures. Two critical temperature thresholds apply: Minimum operating temperature: Rubber turns brittle, loses elasticity, and may crack below this value. Maximum operating temperature: Excess heat causes softening, oxidation, hardening, and permanent deformation, resulting in loss of resilience and bearing capacity. The rated temperature range differs from the actual working temperature. Material formula, manufacturing process, contact medium, and dynamic/static working conditions all affect performance. A comprehensive assessment is required to guarantee a reliable sealing effect.

I.Core Properties of Common Rubbers II.Differences and Applications of Common Rubbers Note: Practical rubber products often contain pigments, so color cannot be used as the sole basis for identification. The most reliable methods are: – Checking the material marking (e.g., markings on oil seals) – Consulting your supplier For simple identification, you can combine: – Oil resistance test (observe swelling after immersion) – Burning characteristics (e.g., CR is self-extinguishing) III.Advantages and Disadvantages of Common Rubbers Natural Rubber (NR) Main Advantages: Excellent elasticity, tensile strength, and tear resistance; good processability. Main Disadvantages: Poor resistance to oil, ozone, and heat aging; narrow operating temperature range. Styrene-Butadiene Rubber (SBR) Main Advantages: High abrasion resistance, heat resistance, low cost, and the highest production volume. Main Disadvantages: Slightly lower elasticity and cold resistance; poor resistance to oil. Butadiene Rubber (BR) Main Advantages: Outstanding elasticity, abrasion resistance, and cold resistance. Main Disadvantages: Poor tear resistance. Chloroprene Rubber (CR) Main Advantages: Good overall performance; resistant to oil, weathering, flame, and ozone aging. Main Disadvantages: High density, average low-temperature performance, and relatively expensive. Nitrile Rubber (NBR) Main Advantages: Excellent oil resistance (second only to fluorocarbon rubber, etc.), good abrasion resistance, and airtightness. Main Disadvantages: Poor cold resistance, ozone resistance, and electrical insulation. Ethylene Propylene Diene Monomer (EPDM) Main Advantages: Superior resistance to ozone, weathering, and aging; resistant to hot water and steam; good electrical insulation. Main Disadvantages: Poor oil resistance; slow vulcanization; poor self-adhesion. Butyl Rubber (IIR) Main Advantages: Best gas and water tightness; heat and aging resistance. Main Disadvantages: Poor tack, slow vulcanization, and poor oil resistance. Silicone Rubber (SI) Main Advantages: Widest temperature resistance range, non-toxic, insulating, and ozone-resistant. Main Disadvantages: Low mechanical strength, poor oil and solvent resistance, and high cost. Fluorocarbon Rubber (FKM) Main Advantages: High-temperature resistance, oil resistance, superior chemical resistance, and aging resistance. Main Disadvantages: Very expensive, poor processability, average cold resistance, and low elasticity. Chlorosulfonated Polyethylene (CSM) Main Advantages: Excellent abrasion resistance, weather resistance, ozone resistance, and good flame retardancy. Main Disadvantages: High cost, poor rebound, and compression set properties. IV. Quick Selection Guide Great elasticity → Choose Natural Rubber (NR) Great wear resistance & low cost → Choose Styrene-Butadiene Rubber (SBR) Oil resistance → Choose Nitrile Rubber (NBR) (general use) or Fluoro Rubber (FKM)(extreme conditions) Weather & aging resistance → Choose Ethylene Propylene Rubber (EPDM) Air & water tightness → Choose Butyl Rubber (IIR) Wide temperature resistance → Choose Silicone Rubber (SI) Super corrosion resistance → Choose Fluoro Rubber (FKM)

Standard O-ring sizes are defined by two core dimensions: inner diameter (d₁) and cross-section diameter (d₂, wire diameter). All major standards follow these two key parameters, together with matching tolerances and standardized series rules. The sizing principles and common standards are as follows: 1. Core Dimension Standards: All standards first establish a standard series for the cross-sectional diameter d2 (wire diameter) (e.g., 1.8, 2.4, 3.1, 5.7, 7.0 mm, etc.), and then match the wire diameter with standardized values for the inner diameter d1. Furthermore, d1 increases in fixed increments to avoid a chaotic array of specifications. 2. Dimensioning Rules: The general notation is d1×d2 (inner diameter × wire diameter). In some cases, the outer diameter (d1+2×d2) may be specified, but the standard core remains based on d1 and d2; 3. Tolerance Specifications: Different standards define upper and lower deviations for d1 and d2 based on size ranges (e.g., small inner diameter/large inner diameter, fine wire diameter/coarse wire diameter) to ensure interchangeability. Main Common Standards (Most Widely Used in Industry)： – GB/T 3452.1 (Chinese National Standard) The mainstream standard in China. It defines a narrow series (1.0–4.0 mm) and a wide series (5.7–12.0 mm) for crosssection diameters. Inner diameters are matched to each crosssection, covering most general industrial applications. – AS568 (American Standard) Widely used globally, especially in hydraulic and pneumatic systems. Each part number corresponds to a unique d₁×d₂ size (e.g., AS568010 = 1.78 × 1.78 mm). Key crosssections include 1.78, 2.62, 3.53, and 5.33 mm, widely compatible with American and European equipment. – JIS B 2401 (Japanese Standard) Divided into Type P (general) and Type G (precision). Its crosssection and inner diameter series differ slightly from GB and AS568, mainly for Japanese machinery. – ISO 3601 (International Standard) Highly aligned with GB/T 3452.1, serving as the unified global basic specification with consistent core dimension series. Key Notes: Standards clearly specify the matching rules for minimum groove dimensions. The Oring inner diameter d₁ and crosssection d₂ must be compatible with the bore and width of the installation groove (typical compression ratio: 10%–20%). This is also a necessary design requirement supporting size standardization.