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Materials
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NAK only uses the highest quality raw materials to achieve high product performance, reliability and durability in each application. To achieve this a wide number of materials are now available to suit most applications demanded of NAK sealing products. In addition to these we would be happy to locate or develop a suitable compound for your specific needs.
Most sealing applications can be satisfied using four major compounds.
| Compound |
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| Temp Range |
-40 to 120
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-30 to 150
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-50 to 250
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-30 to 200
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| Abrasion Resistance |
2
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3
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4
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2
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| Compression Set |
2
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3
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2
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2
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| Cracking Resistance |
3
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3
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1
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2
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| Cut Growth Resistance |
2
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2
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4
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4
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| Flex Cracking Resistance |
3
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3
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2
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2
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| Impact Strength |
2
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4
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3
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3
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| Oxidation Resistance |
2
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1
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1
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1
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| Sunlight Resistance |
3
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1
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1
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1
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| Tear Resistance |
2
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4
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4
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3
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| Weathering Resistance |
2
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1
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1
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1
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* Viton ® is a registered trademark of DuPont Performance Elastomers
Advantages & Disadvantages
| Material |
Advantages |
Disadvantages |
Operating Range & Appearance |
Carboxylated
Nitrile - XNBR |
Similar Properties to standard NBR.
Tough.
Abrasion resistant. |
Reduced cold temperature flexibility. |
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| EPDM |
Excellent resistance to heat, water, steam, ozone and sunlight |
Inadvisable for petroleum service |
-50° C to +150° C |
| Fluoroelastomer |
Wide temperature range - 50/+250 ºC.
Flexibility.
High absorbance of lubricant minimises friction. |
Low tear strength.
Poor abrasion.
Poor resistance to oxidised oils or to EP additives. |
Temperature range is -50°C to 250°C,
Generally red, feels softer and more flexible than other materials |
| Nitrile |
Versatile.
Oil and abrasion resistant.
Good low swell characteristics.
Temperature range
Good processing.
Relative low cost. |
Limited high temperature capability.
Limited high speed.
Not suitable for synthetic oils such as phosphate ester. |
Temperature range is - 40°C to 120°C
Other formulations can cope with higher and lower temperatures
Generally black but red is also common as Silicone substitute |
| Polyacrylate - ACM |
High temperature 150 ºC.
Good resistance to oils.
Good ageing.
Low price. |
Lower resistance to water.
Poor processing.
Low temperature range. |
Temperature range is - 30°C to 150°C
Black with similar appearance to Nitrile |
| Silicone |
Wide temperature range - 50/+250 ºC.
Flexibility.
High absorbance of lubricant minimises friction. |
Low tear strength.
Poor abrasion.
Poor resistance to oxidised oils or to EP additives. |
Temperature range is -50°C to 250°C,
Generally red, feels softer and more flexible than other materials |
| Leather |
Tough.
Good abrasion resistant.
Good tensile strength.
Good low-lube run.
Polishes shaft.
OK with most oils.
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Poor resistance to Water.
Non-homogeneous matrix, very variable.
Becoming scarce and very expensive.
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Will handle temperatures from -100°F to 200°F
Safer range is - 65°F to 200°F
Colour brown/beige and fibrous
Generally black but red is also common as Silicone substitute
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| Felt |
Retains grease quite efficiently.
Excludes dust & dirt well. |
Unable to seal oil which seaps through the matrix.
Will absorb water causing shaft rusting.
May trap metal or abrasive particles damaging the shaft. |
Temperature range is - 65°F to 200°F.
White, grey or black. Very fibrous mat.
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