EPDM Compound
EPDM Compound
(OP)
Hello i have an problem with EPDM rubber diaphragm (membrane).
I use this membrane in pressure application sensor. When pressure increase, the diapragm make an movement and i measure this movement.
The problem is that with time the EPDM rubber chanhe her characteristic. After 2 or 3 days i see that at first day calibrated value is changed.
I also do not know what to measure on rubber diaphragm, is it hardness of rubber the right data?
Do you have any idea how cen i improve this?
Is silicon rubber bether in stability with time?
I use this membrane in pressure application sensor. When pressure increase, the diapragm make an movement and i measure this movement.
The problem is that with time the EPDM rubber chanhe her characteristic. After 2 or 3 days i see that at first day calibrated value is changed.
I also do not know what to measure on rubber diaphragm, is it hardness of rubber the right data?
Do you have any idea how cen i improve this?
Is silicon rubber bether in stability with time?





RE: EPDM Compound
Measureing hardness may mislead you because it only reflects the modulus at the surface of the part and is more likely to change quickly due to UV, heat, oxidation.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: EPDM Compound
You may want to look into details of the compound (i.e. is it pure EPDM, or is there other stuff mixed in?). A large amount of carbon black in your compound, or nitrile rubber mixed in, or some sulfur-type cure agents, can cause the compound to absorb a fair amount of water, and change the way the diaphragm will respond. Try specifying a peroxide-cured EPDM.
RE: EPDM Compound
I am not sure if the problem you describe is maybe a more general problem.
Any elastomer takes its elasticity (that is: it returns to old shape after deformation) from internal network of crosslinks. Unfortunately nearly nothing in this world is perfect and so is any rubber. If you apply a stress and keep it constant (as with your diaphragm) you will see a certain relaxation over time and depending mainly from temperature and chemical environment.
So you have to choose rubber (of any type) with a high level of crosslink density (look for low value of Compression set) or separate the two functions of your diaphragm: sealing with (any) rubber sheet and controling the force by steel spring below.
Hope that helps a bit.
Berti
RE: EPDM Compound