Exudation problem in EPDM compound

[nestorberasain]

Hi, I've a exudation problem on EPDM compound. it's very curious problem.
I use EPDM of hi-content of ethylene and paraphinic process oil. This row materials are used since 3 years w/o problems and now the oil exudes in both raw and volcanized state.
Several test was made in order to be sure of raw materials quality, and them was ok.
Then, I change Nordel by Keltan 5508, and exudation phenomena disappeared. Other test was reeplace Tolliris oil by other paraphinic oil (of lower flash point) in the original formula and results was no exudation.
So,

Nordel4770 + Tolliris 7200 = exudation
Nordel4770 + Dexil 109 = no exudation
Keltan5508 + Tolliris 7200 = no exudation
Keltan5508 + Dexil 109 = no exudation

If I see the Nordel resultas I could say the problem is the oil, but if I compare the results of Nordel vs Keltan I could say the problem is EPDM too.

The dilemma is: The problem is the EPDM rubber or paraphinic oil or there are other factor?
What might be the causes or conditions for exudation occurs?

Can someone help me or direct me to understand this phenomena?


Formula in phR

Dow Nordel IP4770P 100
Cabot N-550 225
Cabol N-660 20
Total Tolliris 7200 155
OZn 5
Stearic acid 1
Sulfur 1,4
MBTS 0,3
TMTM 1,4

Thanks you in advance

 

[ebirinci]

it is the polarity difference. nordel and keltan rubbers are different little in polarity. you need to adjust the oil polarity for your epdm. or change the epdm

 

[tom1953]

It may be that the Nordel 4770 has changed slightly, maybe slightly different in E/P ratio or molecular weight distribution than previous. Similarly, the oil may have changed slightly (maybe in the ratio of paraffinic/naphthenic/polar carbons).

I would question the suppliers of the EPDM and oil, advising them of the problem, and ask them if the recent lots of their product is in any way different from older lots of material that you used successfully.

tom

 

[JDLSHF]

Grettings!

Both comments will be correct. I don't know if nestorberasain receives technical specs of the material, or can run lab tests on reception. It's not the first and will not be the last that sent material is not in specs, even if said specs are sent. And sometimes it is not even the intermediarys' fault, and he is just reselling something that was sold to him already switched.

One thing is for sure: if that formulation was working for that time and out of the blue it does not work, then either there is a change on the EPDM or in the oil (or if you are unlucky, in both). Off hand I would say EPDM is the problem. The manufacturing of this can easily change the E/P ratio and you got an off spec batch. Nevertheless, it's not difficult that the problem be on the oil side. That formula does have heavy loads of carbon and oil, so a light shift in specs of these raw materials might cause your problem.

By the way, your zinc oxide formula shouldn't read OZn but ZnO. Being this post somewhat similar to previous ones, hope it helped.