O-Rings
Additional Information
There are several different standards to choose from when it comes to O-ring dimensions. The most popular in the United States is the AS568 standard for O-ring sizes and tolerances. Maintained by the Society of Automotive Engineers, this standard allows the user to choose from five different cross-sections with inside diameters ranging from 1/32" to 26". Tube fitting boss seals are included in AS568 as 900 series O-ring sizes, and are intended for use in MS33649 (now superseded by SAE-AS5202) straight thread tube fitings. RT/Dygert also offers a wide array of metric sizes, in both standard and non-standard dimensions. As a subset of the metric sizes offered, we also stock many Japanese Industrial Standard (JIS B2401) sizes. If an O-ring with special size or fluid resistance is required, RT/Dygert can provide custom O-rings, specially made to your demanding requirements.
SIZES
MATERIALS
PTFE
RT/Dygert Stock Material
Other Designations
Teflon® (duPont)
Composition
Fluorocarbon resin generically known as polytetrafluoroethylene
Temperature Range
-100 to 500 °F
Description
PTFE is not a rubber compound, but a white thermoplastic resin which can be formed into various shapes by either machining or molding. It is a premium grade material which is often specified in harsh chemical environments where no rubber material is suitable as it is impervious to virtually all fluids and gases. PTFE exhibits very low moisture absorption and can withstand extreme high and low temperatures. It also provides the lowest coefficient of friction of any seal material. One major drawback to using PTFE is its tendency to deform under a continuous load, a phenomenon commonly known as creep or cold flow. Loading PTFE with fillers such as bronze, graphite, glass, or molybdenum disulfide can counteract this behavior substantially. PTFE also has relatively poor elasticity compared to other sealing materials.
Information above applies to the generic material. Specific compounds may exhibit different properties.
Physical Properties*
| Excellent | Good | Fair | Poor | |
| Abrasion resistance | • | |||
| Compression Set | • | |||
| Elongation | • | |||
| Flame resistance | • | |||
| Gas permeability | • | |||
| Low temperature flexibility | • | |||
| Tear resistance | • | |||
| Tensile strength | • |
Chemical Resistance*
| Excellent | Good | Fair | Poor | |
| Alcohols | • | |||
| Aldehydes | • | |||
| Alipathic hydrocarbons | • | |||
| Alipathic solvents | • | |||
| Anhydrous ammonia | • | |||
| Concentrated acids | • | |||
| Concentrated Bases | • | |||
| Ketones | • | |||
| Petroleum oils and fuels | • | |||
| Steam | • | |||
| Weather | • |
*Excellent, good, fair and poor are intended to serve as general guidelines only. Actual testing in the application environment is always recommended.
Information above applies to the generic material. Specific compounds may exhibit different properties.