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Abstract
A new method for measuring the oxygen permeability (Dk) of common polymer membranes based on an amperometric sensor was developed. The system was successfully applied to food wrapping and storing films. The method is based on measurement of oxygen concentration variations in time, by means of an amperometric oxygen sensor (Clark electrode), covered with the polymer film and secured with a proper cap. Measurements were carried out under a constant flow of oxygen in order to be independent of initial oxygen concentration. The oxygen permeability of various commercially available food wrapping films was determined according to Fick's first law of diffusion. The method was tested using a reference material of different thickness, Hydrofilcon-43, with a known permeability value. This method gave more reproducible results compared with the ISO measurement systems. The influence of time, use and hydration degree on oxygen permeability was also tested by exposing the tested films for 36 h to UV radiation and keeping them for 50 days in a dryer under vacuum. Results showed that oxygen permeability is proportional to the degree of hydration of the film.
Acknowledgements
Financial support from the EU and Italian Ministry of Education University and Scientific Research (PRIN 2002) is acknowledged.