EPDM vs SBR Rubber 1

[Savalikom]

Hi everyone!

I am a QC manager for a stove manufacturing company. We are in the process of ordering EPDM components from an overseas supplier. This is after we tested the components with SBR grade rubber and it didn't perform well. My question is, when I receive the EPDM components, what QC tests can I perform to ascertain what has been sent is actually EPDM and not SBR?

 

[tom1953]

What tests did you do that convinced you to switch to EPDM from SBR?

 

[GrahamBennett]

Interesting you should start with parts made from SBR, Savalikom. Why did you do this? How close are the parts to the heat source and to what sort of temperatures are they subjected? It could be that EPDM-based compounds wouldn't withstand the service demands and silicone rubber parts mights be a better option.

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[Savalikom]

Heat Aging. The parts are exposed to heat of up 130C. SBR couldn't withstand that sort of temperatures. Silicone would be the last option if EPDM didn't work but for now it's working fine.

 

[Metten]

Burn a small sample. If the try to smear the ashes and they are very smooth, it probably is EPDM. If the ashes are dry and hard you might have SBR (or other types of rubber).

Properly formulated EPDM with peroxide cure should be able to withstand 130°C. If there is contact with glass, you might want to test contact staining. (glass itself isn't an issue, but special coatings on the glass might be a problem)

 

[Savalikom]

Thanks very much Metten for your response. There is no contact with glass. The EPDM parts will be in contact with galvalume sheet of 0.7mm in thickness. Are there any safety concerns when burning the rubber?

 

[Metten]

Just cut a very small strip: few centimeters long, few millimeters thick. Burn that for 1-2 seconds and extinguish. You should have enough ashes to drop on a paper without the paper catching fire. By the time someone alerts your safety personel, you can get rid of the paper and open a window, only the sooted finger is left as evidence.

(There are more elaborated tests to distinguish the different types CR, NBR etc, but it sometimes requires to inhale the fumes and I don't encourage that.)

 

[Savalikom]

We have safety masks in the factory and a lab with a chimney and an fume extractor. Burning the samples might just be okay. Can you share the more elaborate tests to distinguish the EPDM and SB?

 

[Metten]

EPDM peroxide: often distinct smell (not burnt!), soft dry ashes
EPDM sulphur: smoke has a certain smell, soft dry ashes

SBR: no special mention of the smell after burning, hard dry ashes

NBR: hard and dry ashes, asphyxiating smell

CR: hard and dry ashes, HCl smell (when burning with flame burner and in present of copper wire you get a special colour from copper chlorides) density 1.3-1.6 expected

NR and butyl give sticky ashes and distinctive smells.

etc. The smells might need an experienced nose.


I just burn the mini samples behind my desk. I wait for my colleague, the safety coordinator, to leave the room so that he doesn't have the burning smell. Open a window after burning.
I burn less then half a gram of rubber.

 

[GrahamBennett]

Please, please, please, both of you, be very careful when burning NBR rubber because the combustion products will contain carbon dioxide, carbon monoxide, and more especially hydrogen cyanide.

forumtowers.com

 

[GrahamBennett]

I forgot to mention in my previous post that any Neoprene (CR) based compound will self-extinguish after a few seconds usually when the heat source is removed.

forumtowers.com

 

[Savalikom]

Hi Graham Bennett, am burning a small piece in a hood fitted with fume extractor. We observe the basic laboratory safety rules. The burning only takes 1 min and will happen once every 2 months.