Elastomer Hardness Selection
Elastomer Hardness Selection chart below offers a guideline of composition and general properties as well as general chemical resistance information.
Thermoset rubber materials are available in durometers ranging from 20 Shore A to 90 Shore A, while even harder materials are available for thermoplastic elastomers on the Shore D scale. Commonly, materials hardness range in most general applications from 50 Shore A to 80 Shore A, with the majority of sealing products being made from materials with 70 Shore A hardness. Depending on your specific application, Rahco Rubber will be able to recommend a proper hardness for your rubber material.
In dealing with very hard or very soft materials, some manufacturing limitations will apply. Parts that have a complex geometrical design or deep undercuts are more difficult to manufacture from very soft (less than 30 Shore A) or very hard (greater than 80 Shore A) materials.
| Common Name(s) | Designation (2) | Composition | Min/Max Temp Operating Range (F) (5) | General Properties(1) | General Chemical Resistance (3) | |
| Resistant to: | Attacked by: | |||||
| Neoprene | CR | Chloroprene | -30 F / 212 F | Good Weathering Resistance. Flame retarding. Moderate resistance to petroleum-based fluids. | Moderate chemicals and acids, ozone, oils, fats, greases, many oils, and solvents. | Strong oxidizing acids, esters, ketones, chlorinated, aromatic and nitro hydrocarbons. |
| EPDM | EPDM, EPM | Ethylene-propylene- diene; Ethylene-propylene | -40 F / 300 F | Excellent ozone, chemical, and aging resistance. Poor resistance to petroleum-based fluids. | Animal and vegetable oils, ozone, strong and oxidizing chemicals. | Mineral oils and solvents, aromatic hydrocarbons. |
| Buna-N | NBR | Nitrile-butadiene | -30 F / 250 F | Excellent resistance to petroleum-based fluids. Good physical properties. | Many hydrocarbons, fats, oils, greases, hydraulic fluids, chemicals. | Ozone (except PVC blends), ketones, esters, aldehydes, chlorinated and nitro hydrocarbons. |
| Silicone | Q, Si | Polysiloxane | -80 F / 420 F | Excellent high and low temperature properties. Fair physical properties. | Moderate or oxidizing chemicals, ozone, concentrated sodium hydroxide. | Many solvents, oils, concentrated acids, dilute sodium hydroxide. |
| SBR | SBR | Styrene-butadiene | -20 F / 212F | Good physical properties and abrasion resistance. Poor resistance to petroleum-based fluids. | Most moderate chemicals, wet or dry, organic acids, alcohols, ketones, aldehydes. | Ozone, strong acids, fats, oils, greases, most hydrocarbons. |
| Butyl | IIR | Isobutene-isoprene | -60 F / 250 F | Very good weathering resistance. Excellent dielectric properties. Low permeability to air. Good physical properties. Poor resistance to petroleum-based fluids. | Animal and vegetable fats, oils, greases, ozone, strong and oxidizing chemicals. | Petroleum, solvents, coal tar solvents, aromatic hydrocarbons. |
| Natural, Gum Rubber | NR | Isoprene, natural | -60 F / 220 F | Excellent physical properties including abrasion and low temperature resistance. Poor resistance to petroleum-based fluids. | Most moderate chemicals, wet or dry, organic acids, alcohols, ketones, aldehydes. | Ozone, strong acids, fats, oils, greases, most hydrocarbons. |
| Hypalon (4) | CSM | Chloro-sulfonyl- polyethylene | -40 F / 320 F | Excellent ozone, weathering, and acid resistance. Good and abrasion and heat resistance. Fair resistance to petroleum-based fluids. | Similar to Neoprene with improved acid resistance. | Concentrated oxidizing acids, esters, ketones, chlorinated, aromatic, and nitro hydrocarbons. |
| Urethane | AU, EU | Polyethylene-apdate, Poly (oxy-1, 4, butylene) ether | -40 F / 175 F | Good aging and excellent abrasion, tear, and solvent resistance. Poor high temperature properties. | Ozone, hydrocarbons, moderate chemicals, fats, oils, greases. | Concentrated acids, ketones, esters, chlorinated and nitro hydrocarbons. |
| Viton ® (4), Fluoro-elastomer | FPM | Hexaflouropropylene- vinylidene fluoride | – 10 F / 400 F | Excellent oil and air resistance both at low and high temperatures. Very good chemical resistance. | All aliphatic, aromatic and halogenated hydrocarbons, acids, animal and vegetable oils. | Ketones, low molecular weight esters and nitro containing compounds. |
| Fluoro-silicone | FSi | Fluorocarbon | -60 F / 350 F | Offers superior heat resistance. resistant to cold, oils and solvents of fluorinated rubber. Good for special applications where general resistance to oxidizing chemicals, aromatic and chlorinated solvent bases are required. Narrower Temp range than silicone but better fluid resistance | Moderate or oxidizing chemicals, ozone, aromatic chlorinated solvents, bases. | Brake fluids, hydrazine, ketones. |
| Hydrogenated Nitrile | HNBR | Hydrogenated Acrylonitrile-butadiene rubber | -22 F / 300 F | Excellent heat and oil resistance, improved fuel and ozone resistance (approximately 5X) over Nitrile Good abrasion resistance. Decreased elasticity at low temperatures with hydrogenation over standard nitrile. | Many hydrocarbons, transmission fluids, refrigerants, diluted acids, hydraulic fluids, silicone oils, vegetable and animal fats and oils, water and steam. | Chlorated hydrocarbons, keytones, strong acids. |
| Carboxylated Nitrile | XNBR | Carboxylated Nitrile | -20 F / 250 F | Excellent Abrasion and Tear Resistance, Fair Ozone and Steam Resistance. Poor to Fair Sunlight and Outdoors. Good to Excellent Oil Resistance. | Many hydrocarbons, fats, oils, greases, hydraulic fluids, chemicals. | Ozone (except PVC blends), ketones, esters, aldehydes, chlorinated and nitro hydrocarbons. |
Footnotes
- From the “Sheet Rubber Handbook – Gasket and Packing Materials” publication #IP-40 of the Rubber Manufacturers Association (RMA).
- ASTM D 1418-79
- 1979 Yearbook of the Los Angeles Rubber Group, Inc.
- “Viton” and “Kalrez” are registered trademarks of E.I. Dupont, Inc.
- The temperature range is determined by the base elastomer used. This chart depicts the maximum temperature range for each elastomer. The temperature range for a specific compound may not reach these maximum limits. Higher temperatures may be considered if exposure is short or intermittent.