When designing your next product, there are a myriad of elastomer materials to choose from. Jehbco manufactures all our products from 100% silicone. Is silicone the right elastomer for your application? In this article, we’ll explore the differences between silicone and a common competitor – nitrile – and clarify which material is the best choice for your design.
Acrylonitrile-butadiene, commonly known as nitrile or NBR, has excellent chemical resistance, similar to silicone. However, the two materials differ in many of other properties. The table below summarises some of their key differences.
|-57 °C to 121 °C||-50 °C to 230 °C|
|Great compression set||Excellent compression set|
|Poor weather resistance||Excellent weather resistance|
|Approx. tensile strength 15 MPa||Approx. tensile strength 5 MPa|
|Good abrasion resistance||Poor abrasion resistance|
|Not compatible with: ozone, ketones, esters, aldehydes, chlorinated hydrocarbons, brake fluid, concentrated acids. Some formulations are not food grade.||Not compatible with: hydrocarbon fuels, alkalis and acids, steam over 121 °C, trichloroethylene, aromatic hydrocarbons.|
|Compatible with: hot and cold water, petroleum-based oils and fuels, silicone greases, hydraulic fluids, alcohols, weak acids and alkalis.||Compatible with: ozone, oils, brake fluids, hot and cold water, salt water, high molecular weight chlorinated hydrocarbons, fire resistant hydraulic fluid.|
Both silicone and nitrile exhibit excellent resistance to cold temperatures, remaining flexible down to -50 °C, with special formulations of nitrile remaining flexible to -57 °C (at the expense of other physical properties such as wear resistance). Nitrile can operate to 100 °C, or 121 °C with reduced longevity. Silicone can operate at much higher temperatures, up to 230 °C. This makes silicone the best choice for high temperature applications.
Both materials are resistant to a range of chemicals. Nitrile has excellent resistance to hydrocarbon fuels and oils, making it ideal for automotive fuel applications. Formulations of nitrile containing phthalate plasticizers cannot be used with food or children’s toys. Silicone, on the other hand, is food grade and is often used in food and water processing equipment. For any application, it is important to check that the elastomer is resistant to the chemicals it will come into contact with.
Nitrile has high tensile strength and excellent wear and abrasion resistance. By contrast, silicone has poor abrasion resistance, and for dynamic applications where elastomers must have good wear characteristics, nitrile is a better choice.
Nitrile exhibits poor resistance to weathering, UV and ozone, making it unsuitable for outdoor applications. Silicone has excellent weathering characteristics and is highly resistant to both ozone and UV. For outdoor applications, silicone is a clear winner.
While both materials exhibit good compression set, silicone generally undergoes less compression set than nitrile. This makes silicone a better choice in sealing applications where a long-lasting, reusable seal is required.
For help selecting a material for your application, please contact us with any questions.