brittle PEx pipe

Hello all!

In my hands i have a few pieces of PEx-c pipe (electron ray cross linked polyethylene), which have been part of a ring main tube of a drinking water circuit (hot water). The pipes where put in in 1984 and last year they cracked and - of course - started leaking. The pipes were replaced and the brittle stuff is on my desk now. These bits of pipe are so brittle they break easily and shatter when they fall onto a stone floor. The producer of the pipes says that "the temperature stabilizer" was "used up" prematurely. An immediate google tour did not help me on my questions:

- What are temperature stabilizers for PEx?

- How do they work?

- What could probably "use them up"? (no high temperature stresses

80°C)

Anyone any ideas on this? Thanks in advance for any help!

dave

Reply to
dave.lister
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You ought to consider also hydrolysis as the root cause for embrittlement. Hot water can degrade about anything ...

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Reply to
Rolf Wissmann

There was a lawsuit recently where plastic pipes in homes were repalced with copper pipes free of charge. I don't have the first clue as to where you'd begin to find out any info.

BILL D

Reply to
William DiMenna

hydrolysis of polyethylene? I am having a hard time believing that. It is not chemically cross linked, so no silanes, azo's or whatever else is used, just PE. Oh, those pipes are used in hot water circuits a lot and normally they survive.

Reply to
dave.lister

You are referring to water pipes in polybutylene

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Reply to
Rolf Wissmann

Since the molecular weight of the material is extemely high, you might have better luck with hot xylene, decalin or tetralin, heated to 140 C. (There is not a single known solvent that will dissolve PE ar room temperature) Still the same fire danger as before.

It is also possible that the old material will be degraded but not completely uncrosslinked. In that case, the sample will still swell and not completely dissolve. If you let it sit long enough in the solvent, uncrosslinked material will diffuse out of the matrix and into the excess solvent. If you measure weight of the inital sample, and then dry down the swollen sample, you may see a difference in mass. This mass loss could be compared to that of a new sample.

John

Reply to
John Spevacek

thx all!

And yes, it definitely PE and it is electron beam cross linked. The whole chlorine idea could be a winner here, because in the 80's the use of chlorine in potable water in Germany was still quite common - as opposed to nowadays. Didn't think of that. Thx again.

dave

Reply to
dave.lister

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