Material Specifications
The most important component of an oil seal is the elastomer material. You must consider all environmental conditions and functions of the seal such as:
- Chemical Resistance
- Resistance to high and low temperatures
- Resistance to ozone and weathering
- Resistance to water
- Low Compression Set
- Elasticity
- Cost
Harwal offers many compounds to satisfy almost any sealing application. The chart below shows the limitations and resistance qualities of our most common elastomers. Also included are the advantages and disadvantages of each elastomer.
| Material | Advantages | Disadvantages | Ranges | Substitutes |
| Nitrile (NBR) | Highly cost efficient. Good low temp. capabilities. Excellent wear resistance. Little to no swell in hydrocarbon fluids. | Poor high heat resistance Poor ozone resistance. Poor resistance to lubricants containing sulfur or EP additives, hydrocarbons or oxygenate blends (gasoline/methanol). | -40°F to +248°F -40°C to +120°c | FPM Polyacrylate PTFE |
| Viton® (FPM) | Excellent properties for sealing under high temperatures. Excellent fluid compatibility. Very long usage life | Poor resistance to basic fluids with ph>7. Expensive compared to other materials. | -22°F to +392°F | PTFE |
| Leather | Good dry running capabilities | Higher cost than Nitrile. Poor heat resistance. | -50°F to +200°F -46°C to +93°C | Nitrile FPM Polyacrylate PTFE |
| Polyacrylate (ACM) | Good resistance to EP lubricants. Low swelling when sealing hydrocarbon fluids. Better heat resistance than Nitrile. | Higher cost than Nitrile. Poor low temp. compatibility. Should not be used when sealing aqueous media. | -20°F to +300°F -29°C to +149°C | FPM PTFE |
| Silicone | Good resistance to dry heat. Excellent sealing compabilities in low temp. applications. | Higher cost than Nitrile. High swell properties. Poor dry running compatibility. Poor resistance to some EP additives. | -58°F to +356°F -50°C to +180°C | FPM PTFE |
| Urethane | Good lubricant and ozone resistance. Good abrasion resistance. More durable than Silicone. | Substantial softening when used in applications above 250°F. Poor resistance to hot water or steam. | Please contact your Harwal representative with your specific application. | Urethane cannot be substituted. |
| Teflon® (PTFE) | Superior dry running combatibility. Extremely low coefficent of friction. Excellent chemical resistance. Resistant to hydrocarbon/oxygenate blends. | Poor resistance to abrasion in dry environments. Can be easily damaged during installation. High thermal expansion. | -100°F to +450°F -73°C to +232°C | PTFE cannot be substituted. |