Chemically Resistant O-Ring Seal Material
Chemically Resistant O-Ring Seal Material
- Contact with chemical media will directly cause problems such as expansion, cracking, hardening or failure of O-rings. Therefore, material compatibility is the key to ensuring long-term sealing performance and equipment operation reliability.
- The performance of different sealing materials varies significantly in oil, fuel, steam and various corrosive chemical environments and must be accurately selected based on actual working conditions and application scenarios.
- Use KODA O-Ring’s chemical compatibility page to find the right O-ring material for your specific chemical environment and avoid costly seal failures.
Why do chemical-resistant O-rings easily fail?
Many customers encounter problems such as leakage soon after replacement and material cracking and swelling when using O-rings. The core reason is not poor product quality but a mismatch between the material and the working conditions, which is mainly reflected in three aspects:
- Error in adapting chemical media: Different materials have greatly different tolerances to acids, alkalis, solvents, oils and other media. For example, ordinary nitrile rubber will quickly swell and fail when exposed to acetone, while perfluoroether rubber can withstand most strong corrosive media;
- Superimposed effects of temperature and pressure: High temperature will accelerate the erosion of O-ring materials by chemical media, and high pressure will intensify material wear and deformation. For example, at a high temperature of 150°C, nitrile rubber will age rapidly, while fluorine rubber can still maintain stable performance;
- Ignore the details of working conditions: Dynamic sealing and static sealing, changes in medium concentration, outdoor exposure and other details will affect the choice of materials. For example, dynamic sealing scenarios require materials with both corrosion resistance and wear resistance, while static sealing focuses more on the elasticity and sealing properties of materials.
The core of choosing chemical-resistant O-ring materials is matching working conditions – first clarify your own media type, temperature range, and pressure conditions, and then select materials accordingly, rather than blindly pursuing high-end or low-price.
How Chemical Exposure Causes O-Ring Aging
- The medium penetrating into the material will cause the O-ring to over-expand, become soft, lose rebound, and even deform and extrudate;
- Solvent substances will dissolve or extract the additives and basic polymers in the material, causing the O-ring to shrink, harden, and become brittle;
- Corrosive media such as acids, bases, strong oxidants, etc. will directly destroy the polymer chain and cause cracking, powdering, and cracking;
- High-temperature and high pressure will further intensify chemical reactions and accelerate aging exponentially.
Eventually, the seal will lose elasticity, become permanently deformed, damaged or leak, which will directly lead to equipment shutdown, leakage and safety risks.
Brittleness and cracking
The brittleness increases and cracks occur, which will eventually cause the seal to lose elasticity, become permanently deformed, damaged or even leak, directly causing equipment shutdown, media leakage and safety hazards.
Blisters and swelling
- The penetration of the medium into the rubber will cause the O-ring to swell significantly, become larger, become soft and lose elasticity. In severe cases, the surface may blister, bulge, or even be squeezed out of the sealing gap under pressure;
- Solvent substances will dissolve or extract the additives and basic polymers in the material, causing the O-ring to shrink, harden, and become brittle;
- Corrosive media such as acids, bases, strong oxidants, etc. will directly destroy the polymer chain and cause cracking, cracking, and powdering;
- High-temperature and high-pressure working conditions will further intensify chemical reactions and accelerate the aging rate exponentially.
Eventually, the seal will lose elasticity, become permanently deformed, be damaged or leak, which will directly lead to equipment shutdown, media leakage and safety risks.
Common chemical exposures in industrial applications
- The penetration of the medium into the rubber will cause the O-ring to swell significantly, become larger, become soft and lose elasticity. In severe cases, the surface may blister, bulge, or even be squeezed out of the sealing gap under pressure;
- Solvent substances will dissolve or extract the additives and basic polymers in the material, causing the O-ring to shrink, harden, and become brittle;
- Corrosive media such as acids, bases, strong oxidants, etc. will directly destroy the polymer chain and cause cracking, cracking, and powdering;
- High-temperature and high-pressure working conditions will further intensify chemical reactions and accelerate the aging rate exponentially.
Eventually, the seal will lose elasticity, become permanently deformed, be damaged or leak, which will directly lead to equipment shutdown, media leakage and safety risks.
Hydrocarbon oils and fuels
Hydrocarbon oils and fuels, such as mineral oil, gasoline, diesel, kerosene, hydraulic oil, lubricating oil and various hydrocarbon solvents, are the most common media types in industrial seals. This type of medium will cause obvious swelling, softening and performance attenuation of ordinary rubber. Therefore, nitrile butadiene rubber (NBR) and hydrogenated nitrile butadiene rubber (HNBR) are preferred in material selection. They have excellent tolerance to hydrocarbons, are cost-effective and widely used. Under higher temperatures and more demanding working conditions, fluorine rubber (FKM) can be used, which has better oil resistance, fuel resistance, high-temperature resistance and aging resistance and can meet the requirements for long-term reliable sealing.
Water, steam and alcohols
Water, high-temperature steam and alcohol media (such as methanol, ethanol, isopropyl alcohol, etc.) are also very common in industrial equipment. Although they are weakly corrosive, long-term exposure can still cause swelling, hydrolysis or aging failure of some rubber materials. For this type of working conditions, silicone rubber (VMQ) and ethylene propylene diene rubber (EPDM) are stable and have good water resistance, alcohol resistance and steam resistance. In scenarios where alcohol and some chemical media are considered, fluorine rubber (FKM) can also be used to obtain a more comprehensive chemical resistance and high temperature resistance sealing effect.
Acids, alkalis and highly corrosive chemicals
Acids, alkalis and highly corrosive chemicals are the media that need to be dealt with in industrial sealing. They mainly include strong acids such as sulfuric acid, hydrochloric acid, nitric acid and hydrofluoric acid, strong alkalis such as sodium hydroxide and potassium hydroxide, as well as various strong oxidizing and corrosive solvents. Such media will quickly cause ordinary rubber materials to swell and become brittle. Chemical cracking or even dissolution causes serious sealing failure; at the same time, water, high-temperature steam and alcohol media (such as methanol, ethanol, isopropyl alcohol, etc.) are also very common in industrial equipment. Although the corrosiveness is relatively weak, long-term contact will still cause some rubber materials to swell, hydrolyze or age and decay. For such complex working conditions, the material selection needs to be accurately matched: for strong acids, alkalis and highly corrosive chemicals, perfluoroether rubber (FFKM) and polytetrafluoroethylene (PTFE) are preferred, both of which are extremely chemically inert and can withstand most strong corrosive media; for water, steam and alcohol media, silicone rubber (VMQ), ethylene propylene diene monomer (EPDM) It has stable performance and excellent water resistance, alcohol resistance and steam resistance. If you need to consider alcohol and some moderately corrosive chemical media, you can choose fluorine rubber (FKM), which considers chemical resistance and high-temperature resistance sealing requirements to ensure long-term and stable operation of the equipment.
Outdoor weather and ozone
Outdoor weather and ozone are also environmental factors that industrial seals need to deal with. Long-term exposure of outdoor equipment to sunlight, rain, and alternating high and low temperatures will accelerate the aging and cracking of rubber materials. Ozone (especially ozone generated in industrial environments) will cause oxidative erosion of most rubbers, causing materials to become embrittled, cracked, and lose sealing elasticity. Acids, alkalis, and highly corrosive chemicals are media that need to be dealt with in industrial seals, mainly including sulfuric acid, hydrochloric acid, nitric acid, Strong acids such as hydrofluoric acid, strong bases such as sodium hydroxide and potassium hydroxide, and various types of strong oxidizing and corrosive solvents will quickly cause ordinary rubber materials to swell, embrittle, crack or even dissolve, causing serious sealing failures. At the same time, water, high-temperature steam and alcohol media (such as methanol, ethanol, isopropyl alcohol, etc.) are also very common in industrial equipment. Although they are relatively weak in corrosiveness, long-term contact will still cause swelling, hydrolysis or aging of some rubber materials. For such complex working conditions, the material selection needs to be accurately matched: for strong acids, alkalis and highly corrosive chemicals, perfluoroether rubber (FFKM) and polytetrafluoroethylene (PTFE) are preferred, both of which are extremely chemically inert and can withstand most strong corrosive media; for water, steam and alcohol media, silicone rubber (VMQ), ethylene propylene diene monomer (EPDM) It has stable performance and excellent water resistance, alcohol resistance and steam resistance. Ethylene propylene diene monomer (EPDM), fluorine rubber (FKM) and perfluoroether rubber (FFKM) also have good ozone resistance and outdoor aging resistance, making them suitable for outdoor exposure scenarios. If you need to consider alcohol and some moderately corrosive chemical media, fluorine rubber (FKM) can be used to consider chemical resistance, high-temperature resistance and outdoor ozone resistance requirements, ensuring long-term and stable operation of the equipment.
Common O-ring materials and their chemical resistance
The chemical compatibility of commonly used O-ring elastomer materials is summarized and compared below. The following are sealing materials widely used in various industries and their performance advantages and limitations in chemical corrosion resistance:
| Material | Chemical Resistance | Chemical Weakness | Common Environments |
| Nitrile (NBR) | Oils, fuels, hydrocarbons | Ozone, UV, acids, ketones, steam | Engines, pumps, hydraulics, fuel systems |
| EPDM | Water, steam, glycols, polar solvents, mild acids and bases | Oils, fuels, hydrocarbons | Water systems, HVAC, cleaning agents |
| FKM (Viton®) | Oils, fuels, many acids, solvents, oxidizers | Steam, strong bases, amines, some polar solvents | Chemical processing, refining, fuels |
| Silicone (VMQ) | Water, mild chemicals, ozone, UV | Oils, fuels, concentrated acids, solvents | Food, pharma, medical |
| Aflas (TFE/P) | Steam, amines, caustics, sour gas, oils | Aromatics, ketones, chlorinated solvents | Oil & gas, power plants, chemical plants |
Conclusion
Chemical exposure can have a significant impact on the performance of seals and O-rings. The mechanical properties of the seal are closely related to the chemical structure of its polymer matrix. When exposed to various chemical media for a long time, the material is prone to swelling, softening, embrittlement or cracking, which directly leads to seal failure. There are several proven O-ring elastomer materials on the market, each with specific chemical compatibility. Therefore, accurately identifying all media that the equipment actually comes into contact with (including cleaning agents, disinfectants and other auxiliary chemicals) and selecting matching corrosion-resistant materials accordingly is the key to ensuring sealing reliability. Reasonable material selection through chemical compatibility comparison tables and professional technical guidance can effectively avoid chemical erosion, extend seal life, improve equipment operation safety, and reduce downtime and maintenance costs. Fully understanding and paying attention to the impact of chemical exposure and making targeted material selection and protection are of great significance to improving the overall stability and service life of industrial equipment.
Q&A: O-Ring Materials for Chemical Resistance
Why does it still fail despite the use of corrosion-resistant materials?
There are three core reasons: 1. The material and the medium do not completely match (such as fluorine rubber in contact with low molecular ketones); 2. The temperature/pressure exceeds the material's tolerance range (for example, ordinary fluorine rubber is used at low temperatures of -30°C); 3. Improper installation (scratch the surface, insufficient compression). Solution: Recheck the working condition parameters to confirm material suitability; standardize installation to avoid scratching the O-ring with sharp tools, and ensure that the compression amount meets the requirements (usually 15% to 30% of the O-ring diameter); perform regular inspections and replace aging products in a timely manner.
How to choose between fluororubber and perfluoroether rubber?
The key depends on the severity of the working conditions: 1. If the medium is medium concentration acid and alkali, ordinary organic solvent, and the temperature is ≤200°C, choose fluororubber, which is the most cost-effective; 2. If the medium is highly corrosive (such as hydrofluoric acid, aqua regia), the temperature is >200°C, or the equipment shutdown loss is huge, choose perfluoroether rubber; 3. The budget is limited, and the working conditions are close to the upper limit of fluororubber, you can choose modified fluororubber instead of directly using perfluoroether.
What should I do if the O-ring swells or cracks after being used for a period of time?
Swelling: There is a high probability that the material is incompatible with the medium. For example, if nitrile rubber comes into contact with acetone, suitable materials (such as fluororubber and PTFE) need to be replaced immediately; cracking: if it cracks in a low-temperature environment, the material has insufficient low-temperature performance, and needs to be replaced with silicone rubber or low-temperature modified fluororubber; if it cracks in a high-temperature environment, the material has insufficient temperature resistance and needs to be upgraded to fluororubber or perfluoroether rubber; at the same time, check whether there are excessive stretching, scratches, etc. in the installation.
In the food/pharmaceutical industry, what are the special requirements for selecting corrosion-resistant O-ring materials?
The core requirements are "non-toxic, non-migrating, and in compliance with hygienic standards": give priority to food-grade materials certified by FDA (US) and LFGB (EU), such as food-grade silicone rubber, PTFE, and food-grade fluororubber; avoid using ordinary industrial-grade materials to prevent harmful substances in the materials from migrating into food/drugs; at the same time, choose materials that are non-sticky and easy to clean to reduce bacterial growth.
How does a chemical compatibility chart reduce the risk of O-ring failure?
The chemical compatibility chart can quickly and accurately match the O-ring material and the contact medium to avoid swelling, cracking, hardening and other problems caused by the material's lack of corrosion resistance, reduce selection errors from the source, and significantly reduce the risk of O-ring failure, leakage and equipment shutdown.
