Comparing three techniques to determine the water vapour transmission rates of polymers and barrier films

Barrier films are required for a number of applications such as food packaging or organic electronics to prevent product degradation results from exposure to water vapour and oxygen. In order to determine the effectiveness of polymers and deposited barrier films to inhibit water permeation, the water vapour transmission rate (WVTR) needs to be measured. The calcium test, MOCON instrument and tritiated water permeation can all be used to determine the WVTR, but the values produced by these techniques have not been extensively compared. The WVTR of two polymer substrates and two barrier films deposited onto polymer substrates have been measured using these three techniques. For a polyethylene terephthalate substrate and a MOCON reference film, similar WVTR were observed for all three techniques. For two commercially available barrier films, variable WVTRs were observed and attributed to film defects. WVTR measurements play an essential role in the use of polymers and barrier films to retard water permeation, therefore an understanding of the advantages and disadvantages of each technique is of great importance.