Silicone O Rings
Silicone o rings are an ideal choice for high-temperature applications. They retain flexibility and low compression set over one of the widest operating temperature ranges of all elastomers.
They also offer strong ozone and UV radiation resistance. However, due to low strength and abrasion resistance along with moderate gas permeability, they are not recommended for dynamic applications.
Flexibility
Silicone o rings are constructed from flexible, rubber-like polymers that are able to stretch and coil without breaking. These elastomers, which are developed in two different fashions—liquid silicone rubber or high consistency rubber—can be molded into many shapes and sizes to suit a wide range of applications.
These o-rings are odorless, non-toxic and will not grow mold, which makes them ideal for medical and semiconductor equipment use. They are also ozone and UV resistant, as well as electrically insulating. However, they don’t have good tensile or tear strength and are better suited to static sealing applications rather than dynamic ones.
Nitrile o-rings have great resistance to oil, chemicals and temperature extremes but can’t match silicone in certain aspects. Viton (FKM) o-rings offer similar performance to silicone in regards to weather conditions and chemical resistance but don’t have as much flexibility at low temperatures or as much abrasion resistance.
Durability
Silicone o rings are ideal for static applications with low- or high-temperatures and have excellent flex fatigue and ozone resistance. They also have physiologically neutral and insulating properties. Additionally, silicone is non-toxic and approved for use in food manufacturing.
VMQ rubber, commonly known as Silicone o rings silicone O rings, are made of polymers that contain silicon, oxygen, hydrogen and carbon derived from quartz. Pendant organic groups such as methyl, phenyl or vinyl are added to these molecules to achieve different characteristics. These modifications can increase the o-ring’s ability to withstand temperature extremes, chemical corrosion or physical damage.
Silicone O-rings retain flexibility and low compression set even within one of the widest working temperature ranges of all elastomers. They are resistant to ozone, UV radiation and have good dielectric stability. However, they are not recommended for dynamic applications due to their low tensile strength and poor wear and tear resistance.
Choosing the right O-ring for your application requires careful consideration of the media/substances that will be sealed, temperature requirements and environmental conditions. The sealing experts at Marco can help you choose the best O-ring for your specific application.
Temperature Resistance
When evaluating potential o-ring materials for your application, it is important to consider the operating temperature range. Some materials are better suited to high temperatures than others. For example, silicone o rings offer excellent thermal stability and resist many chemicals and oils. They also have one of the widest working temperature ranges of any elastomer.
This is largely due to the unique chemical composition of the material. Silicone is comprised of alternating silicon atoms and oxygen molecules. It is able to retain its properties at a high level of heat, and can be compounded to be flame retardant or conductive.
Other o-ring materials such as nitrile, elastomer and fluorocarbon rubber (VitonTM) have good chemical resistance, but are less flexible at low temperatures or in environments where the o-ring is exposed to a lot of vibration. In addition, if you are looking for a food-grade seal you must ensure the material is declared and approved for use in contact with aqueous, acidic or fatty foods.
Another good option is a food-safe o-ring made from EPDM rubber, which has excellent ozone and UV resistance as well as good resistance to most chemicals and oils. However, it is not suitable for contact with diluted salt solutions, brake fluid, strong acids or superheated steam.
Chemical Resistance
Silicone O rings are odorless and non-toxic, so they work well in food, medical, and semiconductor applications. They are also resistant to UV damage, corrosion, oils, chemicals, and solvents. However, they do have low tensile strength and poor tear resistance, so they are best used for static rather than dynamic seals.
Nitrile rubber (Buna-N) is another popular choice for O-rings because of its oil, fuel, and solvent resistance. This material is very durable and can withstand high temperatures. However, it does not react well with ethers, esters, ketones, or chlorinated hydrocarbons.
Ethylene-propylene-diene rubber (EPDM) is also resistant Silicone o rings to a wide range of chemicals and has excellent temperature resistance. Peroxide cured EPDMs are especially strong, providing resilience and resistance to cracking.
Tensile Strength
As with most rubbers, silicone has low tensile strength. This can limit its use in dynamic seals, although it’s still an excellent choice for static applications with exceptional environmental resistance.
It holds up against extreme temperatures, UV radiation, ozone, corrosion and many oils and chemicals. It also has good insulating properties and is physiologically neutral, making it safe for medical and food equipment and appliances.
The silicone class of elastomers includes polymers with pendant organic groups such as methyl, phenyl and vinyl. These additions affect properties and allow for a wide range of formulations. GFS carries standard and custom silicone compounds that meet FDA, USDA and 3-A standards as well as EMI requirements.
In addition to injection molded silicone, Stockwell also compression molds electrically conductive silicone for EMI gaskets in a variety of standard and custom geometries. We also offer a broad selection of fluorosilicones, which are more chemically resistant than silicone and can be compression molded in complex O-ring geometries. Fluorosilicones are ideal for defense and aerospace applications.
