Issues with EPDM spinning

[LorenzaG.]

Hello Everyone.
We are polyolefin fiber spinners, and I am currently working on a project using a formulation based on a polyolefin polymer + 20 wt.% EPDM (specifically, Dow's NORDEL IP 4725P).
The formulation is perfectly spinnable, but we are experiencing random breaks. Namely, the process can run smoothly for hours (or even days!), then suddenly encounter continuous breaks lasting (a few) hours, before stabilizing again; this cycle repeats unpredictably.
Since I am familiar with the behavior of the polyolefin polymer, I am confident that the issue originates from the EPDM. The inconsistency appears within the same lot and has affected almost all the lots I have tested so far (at least five).
I do not have experience with rubbers, so I am unsure whether this type of behavior is expected. I have read about potential issues related to variable gel content in rubbers (which could naturally impact spinning); however, Dow states that their NORDEL products are "virtually gel-free."
Has anyone else experienced a similar inconsistency? Any insights or suggestions on how to identify and resolve the issue would be greatly appreciated.
Thank you for your time and attention.

 

[btrueblood]

Nordel will be "substantially gel free" at room temperature. But you are heating the material blend to some temperature to make it soft enough to extrude/spin into a fiber? At some temperature over about 250/300 F the epdm will begin to revert, i.e. the crosslinking induced in curing of the rubber will break down, and areas of the rubber will soften and become a sticky goo rather than a firm elastomer.

 

[LorenzaG.]

Nordel will be "substantially gel free" at room temperature. But you are heating the material blend to some temperature to make it soft enough to extrude/spin into a fiber? At some temperature over about 250/300 F the epdm will begin to revert, i.e. the crosslinking induced in curing of the rubber will break down, and areas of the rubber will soften and become a sticky goo rather than a firm elastomer.

Thank you for your reply.
For spinning, we use EPDM in its as-sold form, meaning as a TPE (not cured or crosslinked). We mix it with the polyolefin polymer, then melt and blend the two polymers, and finally extrude and spin the resulting compound. Indeed, we operate at very high temperatures (spinning can reach up to 280 °C), but since melting, blending, and spinning are carried out under a nitrogen flow, I wouldn’t expect significant material degradation; in fact, the appearance of the extrudate is good, its MFI remains stable and in line with expectations (even during periods when we experience breaks), and overall spinnability is good.
The only issue is the occurrence of random breaks, which appear unpredictably...

 

[btrueblood]

Um, I'm behind the times I guess. I have never heard of EPDM used as a thermoplastic elastomer (TPE), usually these are styrenic block or urethane based copolymers.

But I can't find mention of an EPDM-block TPE in a casual search. For instance, https://en.wikipedia.org/wiki/Thermoplastic_elastomer doesn't mention it?

Do you know which Nordel formulation you are using? Can you tell us what else is in the mix? As far as I'm aware, you would need to add a curative agent (sulfur or peroxide based) to the raw Nordel and mix it, and then expose it to an elevated tempeature for some time to cure it into a solid.

Nordel is a Dow product - here: https://www.dow.com/en-us/search.html#q=nordel&t=All&sort=relevancy