http://www.dcproducts.com.au/documents/ElectronicsBrochure.pdf
JB Weld works fine for me. It has thermal properties just as good as arctic alumina, if not a little better, and the stuff is dirt cheap when compared to AA.
I’ve heard it can be slightly capacitive, but I can’t get any resistance reading on any of my DMMs, all the way to 2000 kohms.
I might try taking the welder to a lump of the stuff, just to see how good an insulator is really is. If 300 amps at 45v DC wont arc to it, id say we’re safe.
After frying two drivers (12volt in, 5A ) and cooking three XML2’ LED’s it appears I have the need for potting compound too
I have seen the recommendation for JB Weld and Carbide grit, but is that better than ready made compound like this
That Potting compound is designed to be mixed in the bag,all in one go,then the bag is opened and it all has to be used,or wasted.This one looks like it can be mixed in batches.I know it only has one fifth the thermal conductance of the other one,but it’s still 10 times more than air (0.025W/m°c),maybe enough.
My 2 centimes.
I am pretty sure that polyurethane Polyurethane is not a great thermal conductive material. It sounds like this kit is intended to be used for vibration and as a moisture barrier.
To me is sounds like to keep things simple is JB weld and like texaspyro said
“Why use boron nitride? Silicon carbide has four times the thermal conductivity, is not hygroscopic, and is dirt cheap. Search Ebay for silicon carbide powder and you will find 1500 grit (very fine powder) for between $10 and $1 a pound.”
BADA BING 
If NeilP can get hold of JB weld,then use that.the engineering toolbox quotes epoxy at 0.35w/m°c.Jb weld is an American product not easily available in Europe.Araldite does not have the same high temperature resistance.
I am in luck, I have seen jb weld at some of out local suppliers:)
What?Do they have Nyogel and Deoxit as well? 
I think that is what the thread is bulding up to.
Be crazy, give it a whirl, let us know how it goes.
remimber its in the name of science!
What do you think of this?
POWERBOND 817/12/300 Black Polyamide
Black, Low Viscosity, High Temperature Resistant, VO Rated, Zero Halogen, UL listed & ROSH approved Polyamide Adhesive.
BOND - FILL - SEAL - REPAIR- INSULATE - ASSEMBLE - DECORATE - REINFORCE & ENCAPSULATE
Developed for potting electronic components, encapsulation, component stabilisation, wire tacking, mechanical protection, low pressure moulding, over moulding of PCB and sensors and product identification and for the bonding of difficult plastics such as flexible PVC.
Extensive Technical Data available: Please refer to enclosed data sheets#
http://www.powerbond.co.uk/products/powerbond_81712300_black_polyamide.php
Just been to my local store and they have a JB Weld display rack with about 30 products. including two or three types of epoxy. Some metal reinforced, plastic filler types etc.
What sort is the sort that is being recommended here?
this thread has all you ever wanted to know(and a lot you didn’t)about JB Weld.
Post 16 has a Wiki link
Thanks, that is interesting info.
but it still does not tell me what version of JB Weld the others here have been recommending.