Other compounds
Other compounds
AU, EU (Polyurethane)
Polyurethanes (Polyester-urethane AU), (Polyether-urethane EU) exhibit outstanding mechanical and physical properties in comparison with other elastomers. Urethanes provide outstanding resistance to abrasion and tear and have the highest available tensile strength among all elastomers while providing good elongation characteristics. Ether based urethanes (EU) are directed toward low temperature flexibility applications. The ester based urethanes (AU) provide improved abrasion, heat, and oil swell resistance.
Over a temperature range of -40°C to +82°C (-40°F to +180°F), resistance to petroleum based oils, hydrocarbon fuels, oxygen, ozone and weathering is good. However, polyurethanes quickly deteriorate when exposed to acids, ketones and chlorinated hydrocarbons. Certain types of polyester-urethanes (AU) are also sensitive to water and humidity. Polyether-urethanes (EU) offer better resistance to water and humidity.
The inherent toughness and abrasion resistance of polyurethane (EU) seals is particularly desirable in hydraulic systems where high pressures, shock loads, wide metal tolerances, or abrasive contamination is anticipated.
CO, ECO (Epichlorohydrin)
Epichlorohydrin rubber compounds are noted for their superior gas impermeability and physical properties over a wide temperature range while maintaining excellent resistance to petroleum oils. It has a stable cycling capability from low to high temperature.
Resistance to ozone, oxidation, weathering, and sunlight are other typical ECO qualities. Service temperatures are -51°C to150°C (-60°F to +300°F). Compounds from this polymer can exhibit a corrosive nature and can be difficult to process in manufacturing.
IIR (Butyl)
Butyl has excellent resistance to phosphate ester fluids such as Skydrol", but has an inferior high temperature limit when compared to ethylene propylene. Butyl exhibits the best resistance to gas permeability and some rocket propellents. For O-ring applications, butyl has been all been replaced by ethylene propylene.
The temperature service range for this material is -55°C to +105°C (-65°F to +225°F).
FEP (Teflon®)
FEP is a copolymer of tetrafluorethylene and hexafluorpropylene. FEP has a lower melting point than PTFE making it suitable for injection moulding. FEP is used for encapsulation with TEFLEX® O-rings.
FEP has a wide spectrum of chemical compatibility and temperature range and excellent aging characteristics. Maximum operating temperature for FEP is +205°C (+400°F). A Teflon PFA encapsulation is available for higher temperatures (260°C).
NBR/PVC (resin blends)
PVC resins are blended with nitrile polymers to provide increased resistance to ozone and abrasion. The PVC also provides a significant improvement in solvent resistance, yet maintains similar chemical and physical properties, commonly noted among nitrile elastomers.
The addition of the PVC resins also provide a greater pigment-carrying capacity which allow better retention of pastel and bright colors.
