Here from the past to save the day!
pHx to the rescue -- lol
I am researching something similar as well, and have found 2 prime candidates! OptiCool biodegradable transformer fluid from DSI Inc., or a mixture called Fluorinert by the 3M corporation
http://www.dsifluids.com/
http://solutions.3m.com/wps/portal/!..._IcFQEAOIxDW4!