Water vapour transmission properties of applied polymer films

Abstract

Abstract The rates of moisture uptake by film-coated tablet matrices containing calcium chloride have been determined as a function of polymer coat formulation, film coat thickness and calcium chloride content of the matrix. The more hydrophilic polymer film formulations were less effective in reducing the rate of moisture uptake by the tablet matrices. A linear relation was observed between rate of moisture uptake and film thickness, in contrast to the log-log relationship obtained in previous work using the same systems cast as free films. Decreasing the calcium chloride content of the matrix caused an overall lowering of the moisture uptake rate. The results indicate that the water vapour transmission characteristics of these polymer film systems are not the same when assessed using the rate of moisture uptake of tablets coated with these films as when using the rate of water vapour transmission through the free films. It is suggested that films should not be accepted or rejected solely on the basis of transmission rates across free films but that due consideration should be given to the more meaningful moisture uptake rates of the film-coated dosage form.