Outgassing from epoxy resins and methods for its reduction

Abstract

Due to the ease of moulding light components of any shape, excellent electrical insulation and nonmagnetic properties of epoxy resins, their use in vacuum systems is quite wide spread. However, their relatively high outgassing rates—approximately one hundred times that of unbaked glass or metals and one million times that of baked glass and metals—is a serious drawback and can cause formidable vacuum problems unless this aspect is duly considered in the design. This effect is usually manifested in impracticably high pumping speeds which would be required to attain pressures below 10 −5 torr (10 −3 Pa), in systems using large surface areas of epoxy. In situations where large epoxy surfaces are unavoidable, some means of reducing the outgassing rate would be desirable. This paper presents the results of many trials in this direction. It was found that outgassing rate can be reduced by an aquadag coating (by a factor of 5), by a vacuum evaporated aluminium coating (by a factor of 10) or by cladding with aluminium or stainless steel foils (by a factor of 20). However, these surface treatments would obviously affect the surface dependent electrical properties of the epoxy.