Eisbaer 200 tube/fittings repurposing

[BobbyBoyGaming]

Hello,

I purchased an Eisbaer 200 a long time ago and I have since been using that radiator with 13/10 tubing and fittings on another system. I would really like to reuse these fittings and this anti-kink spring, but I cannot untighten these fittings. They are EXTREMELY tight. Did you guys put superglue on the threads?
I have tried using WD40 and strong pliers but it's still extremely difficult to untighten these fittings.

Do you have any information or suggestions on how to achieve this?

I also want to know what kind of tubing material is used on these Eisbaer hoses? The plastic looks shinier and less flexible than EPDM. I know it's not EPDM. I suspect this material is why this fitting is so extremely difficult to untighten.
Is this Silicone? or PVC? The tube has a shine to it and it also more difficult to work with than EPDM. That's all I know or have noticed thus far. It does not seem to compress as easily as EPDM.
I want to know so that I can avoid this material forever... LOL..

 

[Eddy]

Brute force is the only thing that will help here. It might help to warm up the fittings so the material expands or becomes a bit more flexible. Otherwise, only pliers will do the job.
This is an 11/8 mm PVC tube like item 17493, a tubing size that is currently dying out. There are hardly any fittings available for this size anymore.