O-Ring Permeation Chart

Learn About O-Ring Permeation Rate and Permeation Coefficients

Permeability or permeation of gases through an O-ring varies by material type; material hardness; degree of squeeze; presence or absence of lubrication; size of O-ring cross section; and the pressure, temperature and type of gas being sealed.

Typically, harder compounds containing more carbon black feature lower diffusion rates. Increased seal squeeze results in decreased permeability. Externally lubricated O-rings can decrease permeability.

FKM Viton® O-Rings are commonly used in vacuum applications due to lower permeation which impacts vacuum pump-down time and the ultimate vacuum level achievable. O-Ring permeation can also affect the accuracy of sensitive sensor and test equipment. O-Ring outgassing or leaching of internal substances can also impact sensor effectiveness. Marco Rubber offers FKM Viton® O-Rings with an additional post cure or vacuum baking resulting in lower outgassing O-Rings.


O-ring Permeation
Q = K A (P1 - P2) / D
Q is the permeation rate (cm3/sec)
K is the permeation coefficient (cm3 cm/sec cm2 atm)
A is the area (cm2)
P1 - P2 is the pressure gradient (atm)
D is the thickness (cm)


Permeation Coefficients (10-8 sccm - cm/sec - cm2 - atm)

Material
HE
H2
H20
N2
CO2
Buna-N
8
2.5
760
0.1
25
EPDM
25-30
16-18
6-7
85
Silicone
250
75-450
8000
200
2000
Fluorosilicone
140
80
40
400
FKM Viton ® A
9-22
1-2
40
0.05-0.7
5
FKM Viton ® GF
30
3
2
Markez ® FFKM
60-80
6-8
90-100
8-12
KEL-F
0.1
0.1
0.5
PTFE
0.4
0.14
0.12
Polyimide
1.9
0.1
0.3
0.2


Have Questions About Your Specific Application?

Connect With an Expert
  • Expert product, application and design assistance
  • Trusted by 14,000+ customers
  • Fast response (usually within hours)