Is EPR (Ethylene Propylene Rubber) bad for potting into penetrators

General Discussion
1

Hi,

I used EPR (Ethylene Propylene Rubber) cable for my thrusters. I am just about to pot it into penetrators, but now I’m worried it wont bond and let water past. I am using G/Flex 650 epoxy. Can anyone tell me if I’m ok to proceed?

Thanks.

2

The only way to know for sure is to do a bonding test. Get a chunk of aluminum, clean and/or abrade it, lay down some lines of epoxy, and then put samples of your EPR cable in them. You can prepare the cable samples in different ways, such as abrading the cable or just giving it a simple wipe with acetone. Once the epoxy has cured, try to pull the cable off of the aluminum, and see which debonds first, the cable or the aluminum. If the cable and the epoxy are compatible, the epoxy should pull off of the aluminum first.

And please let us know how it all goes, so the rest of the forum can learn about this particular combination…

-W

2 Likes
3

That sounds like a good idea. Does it matter if I clean with Acetone or Isopropanol? Or do both? Would you suggest keeping the aluminium the same, say sanded and cleaned with Isopropanol?
Thanks for suggestion. Ill report back with outcome.

4

For Polyurethane jackets (that’s the jacket most commonly used for underwater cables), the acetone eats away a bit at the jacket, giving it a micro-etched finish. That’s why Blue Robotics sells the acetone wipes in their store. I don’t know whether isopropyl alcohol would do the same, but I’m guessing not.

That would be a good thing to do a pull test on - have one small sample that’s just been cleaned with isopropyl alcohol, one with acetone, and a third that’s been mechanically abraded, then cleaned with IPA or acetone.

-W

5

Ok I did the test. Its probably not very scientific, but here we go.

IMG_56291
IMG_562911920×1440 290 KB

Aluminium sanded and wiped with Isopropanol. Cable from left

  1. cleaned with Isopropanol
  2. sanded and cleaned with Isopropanol
  3. cleaned with acetone
  4. sanded and cleaned with acetone

The outcome

IMG_56331
IMG_563311920×1440 290 KB

So everything stuck. The two sanded ones actually stayed stuck to aluminium and tore the rubber jacket, but I think that is more a case of more glue on aluminium.
The epoxy stayed stuck to the two that peeled off the aluminium, but where a few bits of epoxy stayed it tore the rubber jacket to.
In conclusion, to me that looks like it will be just fine no matter what method I use.

What do yous think?