I have a question that maybe someone could answer.

My company has tubing that is a proprietary blend (only two people in the company know what it is). Lets just say it is similar to nylon. One end of the tube is hermetically sealed. The other end needs to connect to an aluminum tube line. We are having a lot of trouble finding a fitting that is leak proof for our application.

It must remain nitrogen pressurized to 100PSI while going through thermal cycles of (75F, 200F, -75F). Of course it will increase and decrease with respect to the high and low temperatures, but in the end it should be back to 100PSI at ambient.

We have tried various sized aluminum Swagelok fittings with little success. It seems that the high temperature portion of the cycle relieves some stress in the tube, and when the temp drops, the nitrogen leaks out of the Swagelok fitting.

I also tried using fittings made of various plastics (Kynar, Polypropylene) in hopes that the CTEs would be similar. Unfortunately, they could not handle the pressure and would blast off during the high temp cycle.

Any suggestions?