Machinable Material with low thermal conductivity 3

[triage]

Is there a cost effective material alternative to aluminium which is machinable, but has a low thermal conductivity.

Currently prototyped a component machined from a hardened block of JB Weld.

It would be an advantage to purchase a material which is already in block form and could stand up to 700 Deg F.

The material does not need to conduct electricity, but should have about the same hardness / strength as Al.

 

[CoryPad]

There is no polymer with the same hardness as Al.

How low does the thermal conductivity need to be? Titanium has less than 1/10th the conductivity of Al.

If you really want a polymer, and with a 700 deg F temp, you are looking at stout ones like epoxy, PPS, PEEK, etc. These are available as shapes from various vendors.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[patprimmer]

Have you tried resin impregnated hardwood.

Have you tried concrete.

Regards

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[triage]

corypad,

Titanium is a bit expensive.
Looking for blocks, 2" X 4" X 4".

PPS and PEEK have too low of melting point (<500 Deg F)and/or or get too expensive for more exotic compositions, otherwise ok.

Epoxy is essentially what we are using for prototype, as mentioned, however has a thermal operating range of ~550 Deg F.

Patprimmer,
Concrete is not very machinable and hardwood... does not hold up to 700 Deg F.

Thanks for the contributions, the search goes on.

 

[IRstuff]

Perhaps a machinable ceramic:

http://www.crystexllc.com/pb_docs/MMDataSheetMACHINABLE_FINAL__8-24_.pdf

http://www.ecsceramics.com/cercoa/ceramics.html

TTFN

FAQ731-376

 

[jedward]

how low must the thermal conductivity be? if very low
Corning's MACOR should be considered
low thermal conductivity, excellent electrical insulator,
thermally stable to about 1000C and machinable

how strond must it be?
aluminum silicate is good but possibly too soft

 

[Demon3]

If you look around you can find special epoxies that stand up to higher temperature, 300C and above. You might try the high temp polymers from Solvay such as Torlon. I think you can get blocks of that to machine from a company called Piper Plastics.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[btrueblood]

Foamed silica blocks, see

http://www.cotronics.com:

http://www.cotronics.com/vo/cotr/cm_machinable.htm

Sintered boron nitride (not crystalline) is low conductivity and quite machinable also.

 

[triage]

IRStuff, jedward, demon3 and btrueblood, thanks for your guidance. It looks like a machinable and castable ceramic is probably the only choice.

I am awaiting pricing information and hope that the cost is not prohibitive.

There is always concrete as a backup option(lol)!

 

[Compositepro]

Polyimdes and BMI's (bismaleimide) can be used at temperatures up to 700F, particularly if you use fiber or filler reinfocement. But you won't find off-the shelf blocks of material. Is your application for a few prototypes or potentially larger volume?

The other important questions are the loads on the part and service life needed. Thermal stresses will be a big factor on part life.

 

[triage]

Compositepro,
In the process of prototype development, however we need a solution which is cost effective and manufacturable, so that when the design transitions to production, we are not limited by an exotic solution.

Thanks for your contribution