Potting: Converting Durometer to Elastic Modulus

[MarkUMSU]

I'm working to select an elastomer to pot some electronics for use in high vibration. It could be helpful to know the elastic modulous of resins, but manufacturers typically report hardness.

I know that there's no direct anylitical conversion between durometer and modulus of elasticity, but does anyone know of a graph, guideline, or equation that makes some reasonable assumptions to make approximations without doing something more rigorous involving viscoelasticity?

This is an interesting starting point:

http://www.simritna.com/catalog/o-ring/98physics_rubber.htm

but I'm also interested in higher values than they report.

 

[gfbotha]

Thanks for the link you mentioned! - as you said, this kind of data is not readily available.

The hardness vs Young's modulus graph appears to give initial (tangent) modulus. E.g. hardness of 80 equals a modulus of 8.6 MPa. This is in agreement with a graph in the Shock & Vibration Handbook by Harris and Crede. As you probably know, this moduli are only good for small deformations. Modulus at 100% strain will of course be much lower.

But, you mentioned you are interested in higher values... Did you notice that the IRHD scale only goes up to 100 and beyond 95 it really gets asymptotic?

Be aware that you also get moduli listed at different frequencies (Hz) and of course temperatures.

For your application you may also have to look at damping properties; apparently some PU's and butyl rubbers have superior damping characteristics.