Development of water vapor transmission rate measuring device using a quadrupole mass spectrometer and standard gas barrier films down to the 10-6 g m-2 day-1 level.

Water vapor transmission rate (WVTR) measuring devices with a quadrupole mass spectrometer (QMS) have an advantage in measuring low WVTRs because measurements are taken under an extremely low background of water vapor by realizing ultrahigh vacuum conditions. Here, the reliability of the QMS measurements was improved by including a porous plug with known molecular conductance in the device to generate a reference molar flux for in situ QMS calibration. Then, standard gas barrier (SGB) films made from a clay-polyimide nanocomposite film were also developed and used to validate the measurement. The measurement results for the SGB films were on the extrapolated calibration curve obtained with the porous plug down to WVTR at the 10-6 g m-2 day-1 level within the estimated measurement uncertainty.