Distinguishing the differences between silicone rubber O-rings and other elastomer O-rings can help you accurately match the working conditions and control costs. This article serves as a sourcing guide and will analyze multiple aspects of silicone and rubber O-rings for you. Hope to help you choose the materials that are more suitable for your business.
What Are Silicone O-rings?
Silicone O-rings are made of silicone elastomer. This material has outstanding properties. Silicone elastomers are synthesized from siloxane polymers derived from silicon, oxygen, carbon and hydrogen, and it possesses unique characteristics such as chemical stability, high-temperature resistance, and biocompatibility.
However, its cost is usually higher than that of ordinary rubber, but its long service life can improve its cost-effectiveness. If the working conditions of your industry are harsh and ordinary sealing components are prone to failure, silicone O-rings are more suitable for you.
Common Applications of Silicone O-rings
Silicone O-rings are widely used in industries that have high requirements for safety and resistance to extreme conditions:
- In the medical field, they are used in sterile equipment and need to pass tests such as USP Class VI and ISO 10993.
- In the food processing industry, because silicone O-rings are non-toxic, flexible, and capable of withstanding a wide temperature range, they are very suitable for contact with food and need to meet the standards of FDA 21 CFR 177.2600, LFGB or EC 1935/2004.
- In aerospace applications, they can function properly in both high-temperature and low-temperature environments, making them crucial in aerospace sealing. Especially for FVMQ (fluorosilicone) O-rings, they must comply with the AMS-R-25988 standard.
- In the automotive industry, as a manufacturer in the automotive supply chain, your factory needs to pass IATF 16949. Silicone O-rings perform well in high-temperature environments and are commonly used in static sealing applications, gaskets, and connector seals.
What Are Rubber O-rings?
Rubber O-rings are made of synthetic materials such as nitrile, EPDM or chloroprene rubber, and they are more commonly used in standard applications. These sealing rings can form a tight seal between two or more components, preventing the leakage of liquids or gases.
The temperature range of rubber O-rings is relatively limited, and they may age more quickly under extreme temperatures. However, if your application is mostly of medium conditions, rubber O-rings have good durability and their cost is usually low, making them an economical choice for you.
Common Applications of Rubber O-rings
Rubber O-rings have extremely high versatility and are used in numerous industries:
- In industrial machinery, they perform exceptionally well in fluid systems where pressure needs to be considered, as they can achieve sealing under pressure.
- In pipeline engineering, rubber O-rings are used in faucets, valves, and pipes to prevent leaks and maintain system integrity. Rubber O-rings are the preferred material for water-based applications.
- The automotive industry also relies on NBR and FKM O-rings in components such as pistons, valves, transmissions, and other components, as reliable sealing is crucial for preventing liquid leakage and ensuring optimal performance.
- In the construction field, rubber O-rings help seal the joints of various machinery and prevent leaks.
Silicone O-rings vs. Rubber O-rings: Key Differences
Temperature Resistance
Silicone has outstanding heat resistance and is suitable for harsh high-temperature cases such as automotive engines and industrial ovens. Most ordinary rubber O-rings have a narrow temperature tolerance range and are only suitable for normal temperature operations, and are not suitable for extreme temperature environments.
The following table compares the temperature resistance performance of silicone and different types of rubber, and you can refer to it for selection:
| Material Type | Continuous Operating Temperature Range | Intermittent / Peak Temperature Resistance | Brittle Point (Low Temperature Limit) | High Temperature Failure Mode |
| Silicone | -60°C to 230°C | Up to 250°C (short-term) | -62°C to -75°C | Hardening, loss of elasticity |
| NBR (Nitrile Butadiene Rubber) | -40°C to 120°C | 135°C – 150°C | -55°C to -40°C | Hardening, cracking |
| HNBR (Hydrogenated Nitrile Butadiene Rubber) | -30°C to 150°C | 165°C | -40°C to -30°C | Hardening |
| EPDM (Ethylene Propylene Diene Monomer) | -55°C to 150°C | 170°C | -60°C to -55°C | Softening, degradation |
| Fluoroelastomer | -20°C to 230°C | 275°C | -25°C to -20°C | Hardening |
| Neoprene | -40°C to 120°C | 135°C | -45°C to -40°C | Hardening |
| Polyurethane Rubber | -30°C to 90°C | 110°C | -40°C | Softening, melting |
Tips: The data in the table represents a typical range, not absolute values. The specific data of the material depends on the formula.
Durability and Service Life
When choosing the materials, you should also consider the durability characteristics of the two types of sealing rings. Because the silicone O-ring is resistant to ultraviolet rays, ozone and weathering, it is more suitable for products used in outdoor and open-air environments.
While the NBR and PU O-rings have better tear resistance and wear resistance, making them more suitable for mechanical applications that undergo continuous friction and pressure. At the same time, you must first distinguish the application conditions before making a choice.
Because static seals are more suitable for using silicone O-rings, such as for furnace doors, pipe flanges, and other fixed applications. Silicone is generally less suitable for high-wear dynamic sealing applications because of its relatively low tear and abrasion resistance.
For dynamic seals like cylinders, rotating shafts, and pump bodies, it is recommended that you choose nitrile, HNBR, PU, PTFE and fluororubber O-rings to avoid rapid wear and damage caused by silicone.
Chemical Resistance
Chemical resistance is also an important reference criterion when selecting materials. Silicone O-rings generally offer good resistance to water, ozone, oxidation, and many dilute acids and alkalis, and are suitable for the chemical, pharmaceutical, and food industries.
Ordinary rubber O-rings except for EPDM, have excellent performance in resisting oil and fuels, but are not resistant to strong acids and strong solvents. They are mostly used in conventional industrial applications.
If your product is often used in oil-based environments, nitrile rubber has outstanding oil resistance and is more suitable; while silicone and EPDM rubber are prone to swelling when in contact with oil products and are not suitable for such applications.
Cost Comparison
When you make a purchase, the first thing you should consider is the cost issue. Ordinary rubber O-rings have abundant supply and low cost, with excellent cost-performance ratio. Silicone O-rings have excellent performance, but the raw materials are special. Although the price is not the highest, it is still relatively high compared to ordinary rubber O-rings.
The pricing of O-rings varies significantly depending on factors such as size, hardness, material grade, certification requirements, color, and order quantity. Therefore, the data provided in the following table is only a rough reference and not a fixed price:
| Material | Relative Cost Index |
| NBR | 1.0 |
| EPDM | 1.2–1.8 |
| Silicone | 2–4 |
| HNBR | 3–6 |
| FKM | 5–10 |
| FVMQ | 10–20 |
| FFKM | 50–500+ |
In small batch production, since the costs of mold allocation and material switching account for a higher proportion, the premium for high-performance materials is significantly higher. If you only make small-scale purchases, you will find that the price difference is even more pronounced.
You can make your purchasing decisions based on the suggestions in the following table:
| Application | Recommended Material | Unit Price Tier | TCO Recommendation | Reason |
| General industrial hydraulic systems | NBR | Low | Optimal | Sufficient performance with the lowest price |
| Food processing equipment | FDA-grade Silicone, EPDM, PTFE, FKM | Mid | Optimal | FDA-compliant materials are selected based on process and cleaning requirements |
| Medical devices | Medical-grade Silicone (common), TPU, TPE, EPDM, FKM | High | Application-dependent | Required to meet compliance standards |
| Automotive fuel systems | FKM | High | Optimal | FKM typically provides longer service life than NBR in high-temperature fuel-system environments. |
| Outdoor and solar applications | Silicone / EPDM | Mid | Depends on operating conditions | EPDM is more cost-effective, while silicone offers longer service life |
| Steam service environments | EPDM | Mid | Optimal | Best cost-performance ratio |
FAQ
Are Rubber O-rings Suitable for Food Applications?
Rubber O-rings made from FDA-compliant compounds can be used in food-contact applications. However, silicone O-rings are often preferred because food-grade silicone compounds are widely available and perform well across a broad temperature range. Rubber O-rings are generally not recommended for use.
How Long Do Silicone O-rings and Rubber O-rings Last?
Under ideal conditions, a silicone O-ring can be used for 8 to 10 years; while the service life of different types of rubber O-rings varies: NBR can be used for about 6 years, and EPDM can last for 10 to 15 years. However, in actual applications, the service life is affected by multiple factors and may be significantly shortened.
Are Silicone O-rings Superior to Rubber O-rings?
This depends on the application. Silicone O-rings perform better in high-temperature environments, while rubber O-rings are more cost-effective and thus more suitable for general purposes.
What Are the Most Common Failures of Silicone and Rubber O-rings?
The common failure situations include: the O-ring becomes flattened and fails to rebound, resulting in leakage; the O-ring swells due to its volume increasing and becoming softer; because it exceeds the temperature resistance limit, the surface of the O-ring hardens and cracks appear, etc.
What Special Precautions Should Be Taken When Installing Silicone O-rings?
When your workers are installing, they should avoid excessive stretching because silicone has poor tear resistance. The stretching during installation should not exceed 8%.
Also, remember to use lubricants, which can reduce installation friction and lower the risk of damage. However, the lubricant must be compatible with both the O-ring material and the operating medium.
By inspecting the installation path, your workers can ensure that there are no sharp edges or burrs in the installation path, and it will not damage the silicone O-ring.
Why Is Compression Set Critical for O-ring Selection?
The compression set will affect the service life of the O-ring. The greater the value, the faster the sealing force is lost and the higher the frequency of replacement. Frequent leakage or replacement will damage your brand reputation and customer satisfaction.
Final Thoughts
Legensilico, as a professional manufacturer of silicone, can provide you with high-quality silicone O-rings. We also offer customized services for silicone O-rings to meet your various specifications and color requirements. If you are interested in our products, please feel free to contact us at any time.
