Shrinkage Testing for EPDM Material

Troy Tipps

Registered
Is there a standard for testing shrinkage in EPDM rubber? We have a customer asking us to do shrinkage testing, but we are more comfortable doing it if there is some standard we can reference. There is an ASTM standard for SBR, but I can't find anything for EPDM or unspecified rubber compounds.
 

Jim Wynne

Leader
Admin
Please tell us more about what your company does, and why your customer is interested in this testing.
 

Troy Tipps

Registered
We produce rubber compound for various industries. The customer in question extrudes parts for the automotive industry (I believe sealing systems) with this compound. They are wanting shrinkage results from the material but don't have a spec they want us to test to. Without a standard, the results we get are of limited (at best) value. They want to try to control shrinkage on the final part and want to start by determining the amount that is inherent in the material. We want to give them data that will help if their efforts but it's difficult to provide without a spec we can both reference.
 

Jim Wynne

Leader
Admin
You need to tell the customer that no testing can be done in the absence of a standard that they specify. There are all kinds of things that can go wrong and provide unreliable results otherwise.
 

Troy Tipps

Registered
That's pretty much what I was thinking but I was hoping to find a standard that I could suggest since they are starting from scratch and have a goal without a path to reach it.
 

Miner

Forum Moderator
Leader
Admin
I worked in automotive sealing systems (EPDM) for about 10 years. They are barking up the wrong tree. Shrinkage has always been a problem in sealing systems. There are simply too many variables. The polymer is just one of those. The amount of tension during extrusion, the amount of shear introduced during extrusion, the type of carrier (e.g., woven wire), curing temperature, the percent of cure, the formulation (e.g., reinforcing materials), the ambient environment on the vehicle, etc. That is why the automotive engineer designs the weather-strip longer than the opening to allow for the shrinkage. This is the type of question that comes from someone with minimal experience in the industry.
 
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