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8/3/2019 Pages From O-Ring Handbook_Parker
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-8 Parker Hannifin Corporation • O-Ring Division2360 Palumbo Drive, Lexington, KY 40509
Phone: (859) 269-2351 • Fax: (859) 335-5128www.parkerorings.com
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Parker O-Ring Handbook
The extraction of plasticizer from a seal material is sometimescompensated for by partial absorption of the contact medium.This situation however, can still lead to unexpected shrinkageand resultant leakage when an elastomer dries out and theabsorbed fluids evaporate.
A chemical reaction between sealed or excluded medium and
the elastomer can bring about structural changes in the formof further crosslinking or degrading. The smallest chemicalchange in an elastomer can lead to significant changes inphysical properties, such as embrittlement.
The suitability of an elastomer for a specific applicationcan be established only when the properties of both the me-dium and the elastomer are known under typical working conditions. If a particular seal material suits a medium, itis referred to as being “compatible” with that medium. SeeTable 2-2 for a comparison of the properties of commonlyused elastomers.
2.4 Physical and Chemical Characteristics
In addition to the basic elastomer descriptions, it is helpfulhave more information on the important physical and chemicalproperties of various elastomer compounds. This informationis needed to provide a clearer picture of how physical andchemical properties interact and affect the proper selection
of an effective seal material. Among the more basic physicalproperties that have to be considered are:
2.4.1 Resistance to Fluid
As used throughout this handbook, the term “fluid” denotesthe substance retained by the seal. It may be a solid, a liquid, agas, a vapor or a mixture of all. (The term “medium” — plural“media” — is often used with this same meaning intended.)
The chemical effect of the fluid on the seal is of prime impor-tance. The fluid must not alter the operational characteristics orreduce the life expectancy of the seal significantly. Excessivechemical deterioration of the seal must be avoided. It is easy,however, to be misled on this point. A significant amount of
volume shrinkage usually results in premature leakage of any
Figure 2-3: Temperature Range for Common Elastomeric Materials
-100
-148
-75
-103
-50
-58
-25
-13
0
32
25
77
50
122
75
167
100
212
Temperature °C
125
257
150
302
175
347
200
392
225
437
250
482
300
572
Normal recommended temperature range Extended temperature range for short term only.
Temperature Range for Common Elastomeric Materials
°C
°F
Sttyrene-Butadiene Rubber (SBRrene-Butadiene Rubber (SBR)
Poolyurethaneyurethane Rubberubber (A(AU,, EUU)
Buutylyl Rubberubber (IIR(IIR)
Loow TTemperature Nitrmperature Nitrilele Rubberubber (N(NBRR)
Hiighh Teemperature Nitrerature Nitrilele Rubberubber (N(NBRR)
Hydrydrogenated Nitrgenated Nitrilele Rubberubber ((HNBR)NBR)
Chhloropreneoroprene Rubberubber (C(CR))
Poolyyaccryylateate Rubberubber (A(ACMM)
Etthyylene-Propne-Propylene-Diene-Rubber (EPDM)lene-Diene-Rubber (EPDM)
Flluorosilicorosilicone-Rubber (FMQ, FVMQne-Rubber (FMQ, FVMQ)
TFE/PropropFE/Propropylene Rubber (FEPMlene Rubber (FEPM)
Flluorocarbon Rubber (FKMorocarbon Rubber (FKM)
Peerfluorfluorinated Elastomer (FFKM)ated Elastomer (FFKM)
Siliclicone-Rubber (VMQne-Rubber (VMQ)
Styrene-Butadiene Rubber (SBR)
Polyurethane Rubber (AU, EU)
Butyl Rubber (IIR)
Low Temperature Nitrile Rubber (NBR)
High Temperature Nitrile Rubber (NBR)
Hydrogenated Nitrile Rubber (HNBR)
Chloroprene Rubber (CR)
Polyacrylate Rubber (ACM)
Ethylene-Propylene-Diene-Rubber (EPDM)
Fluorosilicone-Rubber (FMQ, FVMQ)
TFE/Propropylene Rubber (FEPM)
Fluorocarbon Rubber (FKM)
Perfluorinated Elastomer (FFKM)
Silicone-Rubber (VMQ)
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