Silicone O Rings Are Suitable For Many Applications
O-rings are molded elastomer parts placed between two mechanical pieces to create a seal and prevent fluid or gas leakage. O-rings are available in a wide range of materials. Some are more suitable for some applications than others.
When choosing an o-ring, it is important to consider factors like temperature, seal pressure, durometer, chemical compatibility and other properties. Silicone is a silicone polymer that contains silicon, oxygen, hydrogen and carbon derived from quartz with additives like methyl, phenyl and vinyl.
High Temperature Resistance
An o-ring’s ability to maintain its flexibility and resist cracking at high temperatures is one of the most important factors in selecting an appropriate seal. If the o-ring becomes hardened or embrittled, it will lose its ability to seal – resulting in leaks and possible system failure.
Silicone o-rings can be used in a variety of applications that require high temperature resistance because they retain their flexibility and low compression set characteristics over one of the widest operating temperature ranges of all elastomers. Additionally, they offer excellent flex and fatigue life, superior ozone and UV radiation resistance, physiologically neutral properties, and insulating capabilities.
The silicone o-ring material also comes in a food grade Silicone o rings compound (FDA compliant) and a metal detectable version that can be used for medical or pharmaceutical production lines. Additionally, some silicone compounds are produced in a platinum-catalyzed process to achieve an ultra clean, low volatile compound.
Fluorosilicone o-rings are another choice that offers great high-temperature resistance and excellent chemical resistance. However, they do not have good hot air or dynamic performance compared to standard o-ring materials such as nitrile. A variation of this material, fluorosilicone with carbon-fluorine bonds, commonly known as FKM or Viton®, offers improved fuel and mineral oil resistance, but has limited hot air capability.
Excellent Flexibility
Silicone o rings retain their flexibility and low compression set characteristics within one of the widest working temperature ranges of all elastomers. This feature is a big reason they’re often used in electronics, automotive and aerospace applications. They’re also used in medical systems where it’s necessary to have flexible, non-toxic seals and to keep out moisture that can cause fungus.
In addition to their exceptional flexibility, silicone o-rings are also known for their physiologically neutral and insulating properties. They don’t absorb or transfer heat well and they resist corrosion, ozone and UV radiation very well. They’re also resistant to many oils, chemicals and solvents. They’re odorless, non-toxic and won’t grow mold.
When choosing the right o-ring, consider the working conditions, pressure, durometer and size of the o-ring. Also, make sure the o-ring can be installed with ease in the mating component’s groove and that it will stretch enough to fill that space.
When considering nitrile vs silicone o rings, know that nitrile is stronger than silicone and will withstand higher operating temperatures. Nitrile can be cured with peroxide, platinum or liquid silicone rubber (LSR). LSR is injection molded. This makes it easy to create custom o-ring shapes. It’s also very clean, making it a popular choice for food and semiconductor applications. It can be compounded to be electrically conductive, flame retardant or to have high or low ozone resistance.
Low Volatile Matter
The low volatile matter content of silicone (VMQ) O-rings makes them an excellent choice for static applications where air and other gases are not present. They can be used with medical systems and other sealed areas where the o-ring must be resistant to leachables and extractables, as well as high purity water, alcohols and chemicals. They are also USP Class VI certified for food grade use and can withstand exposure to sterilizing agents.
Silicone o-rings do not perform as well in dynamic applications due to their poor Silicone O Rings – Supplier tear, abrasion and compression set resistance. Their excellent flexibility and fatigue life are an asset, but they may not be ideal for dynamic sealing situations that subject the seal to cyclical movement and stress.
Compared to other elastomers, nitrile O-rings offer good abrasion and tear resistance and good temperature ranges. Nitrile is a popular choice for automotive o-rings and is available in a variety of durometers. Its popularity stems from its low cost, easy handling and good tensile strength.
VMQ O-rings are typically peroxide-cured. For a more stable and dependable seal, they can be platinum-cured, although this increases the price of the o-ring. Depending on the application, these o-rings can be designed with a variety of cross-sections, including T-shapes and L-shapes. They are also available in molded or unshaped cord form for custom sealing applications.
High Chemical Resistance
Silicone has good resistance to a wide range of chemicals, including oil and fuel. It also has good ozone and UV radiation resistance, is physiologically neutral, and provides insulating properties. These characteristics make silicone an ideal choice for static environments that face environmental and temperature extremes. They’re particularly well suited for environments that require FDA approval for food handling equipment and appliances.
Silicone O rings are available in a variety of colors and compounds. The standard compounds are peroxide-cured and a few are platinum-cured, which requires special production processes and is more expensive. Platinum-cured rubbers provide improved flexibility and low volatile matter, and they can be used in applications where medical grade materials are required.
The material’s high chemical resistance also makes it a popular choice for use with foods, where it prevents contamination and keeps the integrity of the equipment intact. Other options for O-rings in these environments include neoprene, latex and PTFE.
FKM, or fluoroelastomer, is another popular option that offers similar high chemical and thermal stability. Its strong carbon-fluorine bonds make it impervious to a variety of substances, including engine and transmission oils, animal and vegetable grease, brake fluid, and fire-resistant hydraulic fluid. However, FKM is not suitable for use in environments requiring aromatic hydrocarbons, concentrated acids, alkalis and superheated steam. It also has a relatively low tensile strength and limited abrasion resistance, so it is not recommended for dynamic applications.