[modeleng] Re: plastic pipe - why not composite?

Rich, I was / am looking for 275F = 135C, which would be the temperature at 
about 30psi, saturated steam.

It seems that there are some plastics that can withstand that temperature, 
but whether or not they are suitable for steam, and that pressure, is 
another matter.
Plus there would need to be an allowance for safety.

With advances in plastic technology, it looks possible now, and if it isnt, 
I would say will certainly be so in the near future.
Alan


----- Original Message ----- 
From: "R.L. Roebuck" <rlr20@xxxxxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Wednesday, April 26, 2006 10:53 AM
Subject: [modeleng] Re: plastic pipe - why not composite?


Hi there Alan,

One more thing you may like to consider: quite frequently where they
appear to have used a plastic for something that you wouldn't have though
they could have used it for, they haven't used a plain plastic.

I would image that if you took a plastic that could take high temp but not
high pressure; and then added something to it to make it into a composite
then this would increase it's strength so that it could take the pressure,
for example a glass filled plastic composite.

I've got part of a truck air cussion spring a few feet away from me, that
will take 5 tonnes of load, and it has a plastic base (with steel inserts
for the bolting points though). It is a glass plastic composite.

The only problem is that you don't want to alter it's properties so that
it would shatter if the steam pressure was too great, you'd really want
it to bulge instead (if you see what I'm getting at).

Possibly someone else on the list could advise about modern plastic
composites, or you could look up a list on the web.

RS has a good list in it's catalogue (you may be able to get to it online
rswww.com or I can send you a scan of the catalogue pages if you want).

They have one - PPS 40% glass filled which they say has high thermal
mechanical strength. max long term service temp 230degC.

Thinking of materials more common to model engineers, Tufnol Carp and
Tufnol Whale are both capable of taking up to 120degC and have good
mechanical strength - what temp did you need again?

Yours,


Rich.


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