Electrical and thermal insulation or isolation.
Sealing — because they can conform to the surface configuration.
Cushioning — because of elastic or plastic properties.
Protects surface finishes.
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Acetal 5614
Good electrical insulator (400-465 v/mil)
Low water absorption rate
Good cold flow resistance
High strength for a non-metallic
Good bearing qualities
High toughness
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Fibre 5602
Low cost
Fair electrical insulator (150-250 v/mil)
Fair mechanical properties
Good thermal conductivity for a non-metallic
(.25 btu/hr/sq ft/°F/ft)
Good cold flow resistance
Not recommended for humid environments
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Fibreglass
• Epoxy 5621
Good electrical insulator (400 v/mil)
High mechanical strength at room temperature
Low water absorption rate
Good dimensional stability
Not recommended for extremely high compression applications
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• Melamine 5621
Good thermal conductivity for a non-metallic
(.29 btu/hr/sq ft/°F/ft)
Best mechanical properties of fibreglass
Good electrical insulator (350 v/mil) particularly in humid environments
Good dimensional stability
Non recommended for extremely high compression applications
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Kapton 5611
Excellent electrical insulator (700 v/mil)
Good for high temperature applications
High dimensional stability
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Mica 5624
Excellent electrical insulator (3000-6000 v/mil)
Excellent for high temperature applications
Relatively expensive to fabricate
Material tends to flake and chip
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Mylar 5622
Extremely good electrical insulator (4000 v/mil)
Less expensive alternate to Kapton for lower temperature applications
Good dimensional stability
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Neoprene 5613
Cushioning properties
Excellent abrasion resistance
Good oil & gasoline resistance
Excellent flame resistance
Excellent sealing qualities
Resilient — tear resistant
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Nylatron (Molybdenum disulfide impregnated nylon) 5615
Excellent anti-frictional properties
Heat resistant to 400°F
Stronger than nylon and better dimensional stability
Not recommended for an electrical insulator
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Nylon (Polyamide) 5610
Good electrical insulator (385 v/mil)
High strength
Good anti-fractional properties
Heat resistant to 300°F
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Phenolics
• CE
5620
Good electrical insulator (225
v/mil)
Good cold flow resistance
Fair water absorption
rate
Moderate shear
strength
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• LE 5620
Good electrical insulator (225 v/mil)
Mechanical properties
not as good as “CE” but better than “XXXP”
Easiest to
fabricate
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• XXXP 5620
Lowest water absorption rate
Good electrical insulator (325
v/mil)
More difficult to
fabricate
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Polyethylene
5617
Low cost — very common plastic
Good
electrical insulator 460 v/mil)
Very low water absorption rate
Good
sealing
properties
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Teflon (polytetrafluoroethylene)
5612
Excellent chemical and corrosion
resistance
Very low water absorption rate
High heat
resistance
Excellent anti-fractional properties
Excellent impact
strength at low temperature
Good electrical insulator (480
v/mil)
Great for frying
eggs!
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| Covers large clearance holes. |
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| The terms washer, shim and spacer are essentially interchangeable and often dictated by personal preference. |