[Materials] GE varnish

1-1. Introduction to GE varnish (GE-7031 or VGE-7031) 

• Commonly used in cryogenic physics as an adhesion with excellent bonding properties for the following reasons;
  - electrical insulator ($10^{15} - 10^{17}Wm^-1$)
  - good high thermal conductivity at low temperature 
  - High dielectric strength of over $10^8 V/m$ 
• suitable for a calorimeter cement at cryogenic temperature 
• Excellent for laminating many types of materials
• may be thinned to the desired application viscosity with a 1:1 mixture of denatured alcohol and toluene 
• Can be used in vacuum ($9.98\times10^{-9}$torr)

1-2. The basic information about GE varnish 

Thermal conductivity at 4K	$3.2\times 10^{-5}$W
Volume resistivity	1013 - 1015 $\Ohm$/cm
Air drying time	15 minutes
Solvent	- 1:1 mixture of toluene and ethanol - Xylene - Alcohol - Acetone
Maximum operating temperature	423 K

 

1.3 Few drawbacks to the usage of GE varnish 

• not available from many equipment stockists because it contains dangerous chemicals
  - often shipped in restricted quantities 
• Can not be used with polystyrene 
  - GE varnish degrades polystyrene through the release of phenol