MEASUREMENT OF THE VAPOUR PRESSURE OF SOME MACROMOLECULAR MATERIALS BY A RADIOMETRIC MANOMETER OF HIGH SENSITIVITY

The possibility of using macromolecular materials in vacuum systems was investigated initially by measurement of the vapor pressures of these materials. Measurements were made of the vapor pressure and its temperature dependence of seven samples of butylmethacrylate of varying molecular masses. The vacuum apparatus and its associated radiometric manometer used in the determinations and the measurement techniques are described in detail. The results show that butylmethacrylate, carefully cleaned of monomer, is a suitable material with respect to the vapor pressure for vacuum systems with pressures higher than 1 x 10/sup -4/ mm Hg as long as the operational temperature is not higher than 50 deg C. Some butylmethacrylate fractions have a vapor pressure low enough to be used in systems with pressures of the order of 10/sup -5/ mm Hg. (J.S.R.)