NASA low outgassing silver filled epoxy is highly thermally conductive

MASTER BOND EP3HTS-TC one part NASA low outgassing rated epoxy delivers enhanced thermal conductivity of 16-17W/(m·K). Product cures rapidly at temperatures around 250-300°F [~ 125-150°C], and has an unlimited working life at room temperature. The material features a thixotropic paste consistency and is not pre-mixed and frozen. Product is suitable for automatic dispensing equipment or manual syringes and can be applied without any tailing. Primarily, it is formulated for use as a die attach and special purpose bonding material. Product is highly electrically conductive, with a volume resistivity of less than 1×10-6 ohm-cm.

click here for more info