O-ring materials explained
Posted on 30/10/2015 Category: O-Rings
The versatile loops of elastomer that we know as O-rings can come in a variety of different materials. Martin’s Rubber has put together this handy guide to explain the various strengths and weaknesses of common O-ring materials. Martin’s Rubber stock a large range of O-rings in NBR (nitrile), FKM (Viton®), silicone, Neoprene and EPDM. The following guide explains the various properties of these materials. It is also worth bearing in mind that we can also offer specialised materials if you have a particularly demanding environment or special performance requirements.
A guide to O-ring materials
Nitrile was a result of the search for elastomers that would withstand lubricating oil and fuels, to allow the design of better sealing systems as technology advanced in the 1930s. Sometimes known as Buna-N or Perbunan, it has good all-round performance with oils and fuels, and it is typically used in applications such as rubber O-rings and gaskets because of this. There are more modern materials available now for enhanced performance and resistance to modern fuels, however Nitrile remains a very common and appropriate solution. Viton® is a fluoroelastomer (FKM/FPM), a high performance synthetic rubber with exceptional properties, particularly when working with aggressive chemicals and fuels. It has very good high temperature resistance, and is commonly used where explosive gases are a concern, making it a commonly selected material within the Oil and Gas industry. However it is not suitable for use in steam. Silicone is a synthetic rubber with exceptionally wide temperature range, from low to high. It has excellent cosmetic and weathering properties and the clear nature of the gum stock means it can be accurately coloured. Unlike other polymers, where carbon black increases the strength of the rubber, the strength is not adversely affected by the choice of colour. Silicone is generally not a particularly high-strength material and does tear relatively easily. However we have special compound grades with much better tear resistance than standard silicones. Neoprene® or Chloroprene was one of the earliest commercially available synthetic rubber material types, and provides a good all-round performance at reasonable cost. It is available in commercial and specification grades, both as moulding compound and finished sheeted forms, and has a wide variety of general engineering applications given its good performance with resistance to fuel splash, weathering and mechanical damage. EPDM is a synthetic rubber with very inert chemical properties which gives it great weathering resistance and good all round performance other than contact with fuels and oils. Widely used as a lower cost polymer, with good processing abilities, however the very inert nature of the material also means it is difficult to adhere to, and this can be a limitation. Many applications for this material exist where external weathering will occur, such as construction and architectural glazing installations.
O-ring cord, back-up rings and specialist fabrications
Martin’s Rubber also offers O-ring cord with standard sections ranging from 1mm to 20mm. O-ring cord has an o-profile but is supplied as an extruded cord and therefore can be cut to the length you require. It can be used as a static seal, where standard sizes are either unavailable or too costly, and can be bonded or vulcanised to the size required. It is available in all the standard materials and supplied in lengths or coils. We manufacture and supply PTFE back-up rings to prevent extrusion of O-rings under pressure. These may be spiral types such as those laid out in BS5106 or solid styles. Plus, we have facilities to fabricate large O-rings in-house, and are also able to mould complex seals with an O-ring cross section. Many material options are available from stock or to special order, and we offer a Kitting service which provides a complete, ready to fit set of parts for repair or OEM applications. Contact us today on 023 8022 6330, or email Email Us, for more details about our entire range of O-rings.