suitable insulation Material for machining

[themroc]

I am looking for insulation Material with low thermal conductivity. It will be used inside a 60mm stainless steel tube as an kind of inlay to reduce the 60mm to a smaller diameter. The Material Properties need to allow for machining, e.g. on a lace or milling machine.

I used Delrin an acetal resin from du pond which has a thermal conductivity of about 0.36W/mK in the past

Does anyone know of something similar which can be used for machining but with a lower thermal conductivity?

It needs to cope with fluidtemperatures (Oil or water) of up to 80°C

 

[unclesyd]

Here is a glass ceramic material (Macor) that may fill the bill. This is just one of the providers, check around.

http://www.accuratus.com/macorfab.html

 

[MintJulep]

How about Lexan? 0.2 W/Mk.

 

[IRstuff]

Macor's thermal conductivity is actually quite comparable to other ceramics:

http://www.accuratus.com/macormats.html

1.5 W/m-K

For the thermal conductivity that you're looking for, expanded foams and plastics are probably it. Polystyrene and expanded polystyrene have thermal conductivities lower that 0.08 W/m-K:

http://en.wikipedia.org/wiki/Polystyrene

Styrofoam has thermal conductivities on the order of 0.02 W/m-K:

http://www.dow.com/PublishedLiterat...foam/pdfs/noreg/179-02548.pdf&fromPage=GetDoc

But they're are probably not machinable, although they can certainly be molded. And it might be possible to use a machinable insert if machining is an absolute requirement.

TTFN

FAQ731-376

 

[thermcool]

Try high density polyethylene with the thermal conductivity in the range of 0.42-0.51 W/mK.

The material have got very good physical properties and can be easily machined.

 

[MikeHalloran]

You could have the Delrin molded in a lattice form that would exhibit low thermal conductivity.

Or you could insert Styrofoam, and roll/crush the inner diameter to whatever you need.


The specification is so far incomplete; you haven't stated a limit on yield strength or elasticity.



Mike Halloran
Pembroke Pines, FL, USA

 

[moltenmetal]

You can "machine" styrofoam, just not to a good surface finish! The same goes with many other rigid foam materials.

I've also seen sintered/porous thermoplastics, but can't recommend a supplier etc. and don't know if they're available in the form of bar.

 

[themroc]

Thanks all this is quiet a lot of information I will see what I can make of it.

I have got a related Question, for insulation purposes we are using for tubes foam insulation from Amstrong Amaflex. Of the shelf this is only available for tube sizes up to 3 inch.

I have got some tubing with a diameter of about 4 inch.
Does anyone know a supplier who can deliver such sizes.
(preferably in the UK)

Maximum Wall temperatures 90°C

 

[MintJulep]

You can get Armaflex in sheets.

 

[themroc]

I am looking for cylindrical slotted forms which adapt perfectly to the tube.

 

[dcasto]

I can't find the name of the material that roto-flow, texas turbines, mafi-trench, and other turbo expander manufacturers use as a thermal barrier in thier machines. The material has vertually no thermal expansion and they machine it to very tight tolerances, you could call one of them and find our, It is a resin based material.

 

[EngAP]

IRstuff: You are correct when stating Styrofoam is probably not machinable. It looked fine to me and was easy to manually cut using a saw but I sent a sample of the material to be machined and the company broke 5 blades trying to machine one piece on their CNC bed.

In the end I went for Celluplank. Approx. 0.69W/m-K so probably not applicable here but machinable and available quickly.