Thermal Mastic – a Non Degrading Heat Transfer Compound
In most refrigerator and freezer systems polyurethane foam insulation is used to fill the cavity or space between an inner refrigeration wall and the outer shell. rv refrigerator repair Evaporator tubing is usually disposed in close contact with the insulation and the tubing is held in place by a high temperature, high conductivity mastic disposed between the tubing and the walls.
During the operation of such systems, the tubing and the insulation will be subjected to considerable stress. This stress can be a significant source of breakdown in the insulating foam. The present invention provides a low cost thermal mastic that does not degrade the polyurethane foam insulation while allowing good heat transfer between the refrigeration tubing and the freezer walls.
The thermal mastic comprises a low viscosity chlorinated paraffin as a vehicle in combination with a finely divided filler and a wetting agent. The proportion of the vehicle and the filler may be varied to provide a mastic composition with particular properties adapted for the method of application and the type of refrigeration system in which it is employed.
For a variety of applications the pumpable thermal mastic can be applied with an ordinary household hose or other device for delivering the material to the area where it is needed. The mastic can be used as a sealer for evaporator coils, freezer plates or fins, and as a sealant for mold heater thermostats in ice makers.
This thermal mastic has been developed to solve the problems associated with prior thermal mastics that contained parafiinic hydrocarbon vehicles. The previous formulations caused cell collapse and cracking in the foam insulation adjacent to the mastic and thereby reduced its useful life.
The mastic has been tested and found to be compatible with the polyurethane foam insulation in refrigeration systems without the degrading of the cellular structure. The mastic is prepared by mixing the chlorinated paraffin vehicle with a finely divided inorganic filler of aluminum silicate clay and calcium carbonate. The mastic is then formulated and a small amount of a wetting agent is added to facilitate dispersion of the filler in the vehicle. The resulting mastic can be used as a thermal mastic in a wide range of applications and is compatible with all types of polyurethane foam insulation.