O-rings prevent liquids or gases from leaking out where this is undesirable An O-ring is circular in shape, has a round cross-section and is inserted into a groove. O-rings are made of synthetic rubber. O-rings achieve their sealing properties through axial or radial compression.
In their factory in Pleidelsheim, our partner Parker manufactures O-rings for automotive engineering, the chemical and biochemical industries, fluid technology, refrigeration and air conditioning technology, the oil industry, medical technology, the aviation and aerospace sectors, the semiconductor industry, as well as many other industry sectors.
Acrylonitrile butadiene rubber (NBR)
Nitrile rubber (NBR) is the common name for this acrylonitrile butadiene copolymer. The acrylonitrile component varies in technical products (18 % to 50 %) and influences the elastomer characteristics. With a high acrylonitrile content, oil and fuel resistance increases, while at the same time flexibility under low temperatures and elasticity decrease, and the compression set deteriorates (see image).
As a compromise, an intermediate acrylonitrile value is often used.
NBR possesses good mechanical characteristics and, in comparison to other elastomers, a high resistance to wear. NBR is not resistant to
weathering and the effects of ozone.
- Heat resistance: up to approx. 100 °C, or 120 °C for short periods (at higher temperatures, it ages faster — this takes place more slowly in hot oils than in hot air).
- Cold resistance: between -20 °C and -55 °C depending on composition
Chloroprene rubber (CR)
Chloroprene was one of the first synthetic rubbers and shows good overall resistance to ozone, weathering, chemicals and aging, intermediate resistance to oil, and possesses good mechanical properties and an extended temperature range.
- Heat resistance: up to approx. 100 °C (120 °C)
- Cold resistance: down to approx. -40 °C
Ethylene propylene rubber (EPM, EPDM)
EPM is a type of rubber manufactured by co-polymerizing ethylene and propylene. With the use of a third monomer, ethylene propylene diene monomer rubber (EPDM) is created, which possesses especially good characteristics for use as seals in phosphate ester hydraulic fluids, and finds widespread use in glycol-based braking systems.
- Heat resistance: up to approx. 150 °C (max. 180 °C in water and steam)
- Cold resistance: down to approx. -50 °C
Rubber made from fluoroelastomers is the most significant development in materials science for seals from the 1950s and is characterized by its wide range of applications. FKM possesses excellent resistance against high temperatures, ozone, oxygen, mineral oils, synthetic hydraulic fluids, fuels, aromatic compounds, many organic solvents and other chemicals. The low-temperature range is disadvantageous, and for static applications lies at approx. -25 °C (some use scenarios and/or materials achieve leak tightness at down to -40 °C); in the case of dynamic stress at -15 to 20 °C. Gas permeability is low and similar to butyl rubber. Special FKM combinations possess higher resistance to acids, fuels, water and steam.
- Heat resistance: up to approx. 200 °C; resistant at higher temperatures for short periods
- Cold resistance: down to approx. -25 °C (in certain cases -40 °C)
Fluorosilicone rubber (FVMQ)
In addition to methyl groups, FVMQ molecules also contain trifluoropropyl groups. The mechanical and physical characteristics are similar to those of VMQ.
However, unlike silicone (VMQ), fluorosilicone has slightly weaker resistance to hot air, but significantly better resistance to fuels and mineral oils.
- Heat resistance: up to approx. 175 °C (200 °C max.)
- Cold resistance: down to approx. -55 °C
Hydrogenated nitrile butadiene rubber (HNBR)
HNBR is obtained by fully or partially hydrating NBR. Significant differences to NBR include a higher temperature resistance (up to 150 °C), and good resistance to oxidative corrosion (e.g. ozone). Furthermore, HNBR also possesses good mechanical properties.
- Heat resistance: up to approx. 150 °C
- Cold resistance: depending on composition, down to -40 °C
FFKM possesses the chemical properties of PTFE (Teflon®) and the elastic properties of FFKM rubber. The handling of FFKM is difficult. Because perfluoro-elastomers are several times more expensive than FKM, FFKM is only used where other types of materials are insufficient. Such applications (aggressive media and/or extremely high termpatures) exist, for example, in the semiconductor industry, in measurement technology and in the chemical industry.
- Heat resistance: up to approx. 310 °C
- Cold resistance: down to approx. -15 °C
Polyurethane rubber (AU, EU)
Depending on the composition of the polyols used, the result is either polyester urethane (AU) or polyether urethane (EU). EU has better hydrolysis resistance.
Compared to other elastomers, polyurethane elastomers possess excellent wear resistance, a high tear resistance and high elasticity. The gas permeability is comparable to IIR.
- Heat resistance: up to approx. 90 °C
- Cold resistance: down to approx. -40 °C
Silicone rubber (LSR, Q, MQ, VMQ)
Silicone rubber refers to a group of materials, of which vinyl methyl silicone (VMQ) is the most often used. Liquid silicone rubber (LSR), which can be dyed almost any color and which can be processed as a 2-component mixture, belongs to this group. The group of silicone elastomers possesses relatively poor tensile strength, tear propagation resistance and abrasion resistance, but possesses excellent special characteristics: Resistance to hot air up to 230 °C and flexibility at low temperatures down to -60 °C, resistance to weathering, good insulating properties, good physiological characteristics and good to intermediate resistance to media.
- Heat resistance: up to approx. 210 °C (for high quality products up to 230 °C)
- Cold resistance: down to approx. -55/-60 °C (for high quality products down to -100 °C)
Styrene butadiene rubber (SBR)
SBR is probably better known under its older names Buna S or GRS (Government Rubber Styrene) which can be traced back to the years between 1930 and 1950, during which a replacement for natural rubber was manufactured in state factories. The raw monomers for manufacture are butadiene and styrol (usually 23.5 %). Approximately two-thirds of world production is made into tires. Seals made of SBR are usually restricted to use in glycol-based braking fluids.
- Heat resistance: up to approx. 100 °C
- Cold resistance: down to approx -50 °C