Chemical migration on vulcanized EPDM products

[Oksitocin]

Dear all,

I hope i will get your help with my problem.
We`ve been using PERKACIT ZDEC in our EPDM compounds since ever.

When we started using the last batch we noticed that the vulcanized products started having some white chemical migration and during time this migration increases and forms like a powder film that doesn`t seem good to the eye so we are afraid our customers will have remarks.
What is your opinion how can we solve this ? Everything else in the recipe compound is ok as far as we noticed - that is how we came to the conclusion that the problem may be from the new batch of PERKACIT ZDEC. Is this possible or is it some mixing mistake or maybe other chemical that is causing this migration ?

Thanks

 

[GrahamBennett]

Does your formulation contain any insoluble or soluble sulfur?

http://www.over50sforum.com

 

[Oksitocin]

Yes it does, we tried to mix the compound without the ZDEC and the products no longer have white migration on them...
It affects the hardness tho, so we had to adjust the N-550 quantity to get the hardness.

 

[GrahamBennett]

Well done, problem solved then. Just remember not to exceed about 0.8phr sulfur in your formulation and not to exceed about 100°C for the batch temperature when the sulfur has been mixed in, otherwise you'll start to get sulfur bloom again.

http://www.over50sforum.com