Conductivity of ebonite 1

[MagneticFlow]

Useing ebonite as a pipe liner and there is a question as to the conductivity of the ebonite.

Delivered from the pipe liner the assembly is dry but, we get very low resistance readings when testing with a megger i.e. 200 - 400 MOhms when we expect to see at least 4 GOhms.

There appear to be lighter coloured streaks across the liner as if some fluid has run over the surface.

Measuring the hardness with a Durometer we notice the lighter patches are softer and we get different resistance readings across the lighter and darker areas.

Is the vulcanising process a factor in controlling the resistivity?

Thanks

 

[RvL04]

MagneticFlow;

I would suggest getting some different conductivity readings (using a different technique). I don't know what technique you used, but the transient plane source method works pretty well for most materials like ebonite. There's a paper on this at

http://www.axelproducts.com/downloads/ThermalConductivity.pdf

that talks about this technique. I'm not 100% sure about your vulcanisation question, but without knowing what the process is you use, I would say there is a pretty good chance that your problems are related to that.

Ron

 

[MagneticFlow]

RvL04

Thanks for the interesting link, the assemblies were rejected and the liner manufacturer did concede that the rubber mix is defective hence the odd coloured patches.

From your post I think we need to address our methods of testing ebonite, we test the liner after it is vulcanised into a steel pipe, so we can't cut bits off for testing!

We typically use a megger set to 1000V and probe across key points, it was only by visual inspection we noticed the discolouration and soft spots. Measuring these and we found the low resistance values.

More work required!