Arrhenius Equation and Activation Energy
Arrhenius Equation and Activation Energy
(OP)
Is there a Arrhenius Plot out there for EPDM? We are trying to calculate the qualified life of an EPDM O ring in a valve using the following equation:
ln(life) = (E/K)(1/T) + Constant
where E = activation energy
K = Boltzmann's Constant
T = absolute temperature
Constant = Intercept of the Arrhenius line
I do not know what the Activation Energy value would be for EPDM(Ehtylene Proylene Diene Monomer) nor the value of the Constant. Can someone please throw some light on this?
ln(life) = (E/K)(1/T) + Constant
where E = activation energy
K = Boltzmann's Constant
T = absolute temperature
Constant = Intercept of the Arrhenius line
I do not know what the Activation Energy value would be for EPDM(Ehtylene Proylene Diene Monomer) nor the value of the Constant. Can someone please throw some light on this?





RE: Arrhenius Equation and Activation Energy
TTFN
RE: Arrhenius Equation and Activation Energy
Elastomer lifetimes are not simply a function of "activation energy", but rather dependent on environment (i.e. pressure, temperature and chemical composition of the working fluid) and manufacturing processes (base rubber composition, mixture additives which are trade secrets, press pressure/temperature). And this is only the start of a huge list of unknowns.
Elongation of life is typically a laboratory experiment conducted in autoclave studies by the manufacturer. On ocassion I have had the need to design and perform studies in explosive decompression and degragation in rubber when an unlisted environment pops up in an application. You cannot simply sit behind a desk and expect to pull a recipe formula from a chemistry book.
IRStuff has it right. The manufacturer would have the necessary information assuming you have the right chemistry for the working fluid.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Arrhenius Equation and Activation Energy
RE: Arrhenius Equation and Activation Energy
What does the valve manufacturer have to say about the life in air service? They should have some idea of the number of cycles if the O-ring is dynamic.
Did you call the Parker Tech Service or did you query a distributer?
Parker at one time was the leader in technical service, but that was several years ago.
Another good source "was";
h
RE: Arrhenius Equation and Activation Energy
RE: Arrhenius Equation and Activation Energy
RE: Arrhenius Equation and Activation Energy
What you actually need to do is specify the operating conditions to the seal manufacturer in detail and ask how often the seal should be replaced. You need to say if the seal is a face seal/rod seal atc, static/dynamic, process fluids (including any contaminants), temperatures with duration and frequency of any cycles, pressure, radiation dose rate (if appropriate).
For the conditions that you quote and if the time at 135C is very limited (a few hours) and very rare (once or twice) and it is a static face seal, I would say that typically qualified life would be 10 years maximum for an EPDM seal.