Abstract
A comparison is made between the salt solution sandwich and wet/dry mixed gas methods of humidifying and controlling moisture in film samples while being tested for oxygen barrier properties on a flowing gas coulometric permeation analyzer. Measurements of the oxygen barrier proper ties, as a function of humidity, of film samples that have moisture dependent permeability are used to assess the effectiveness of each method to control the moisture. Barrier tests are specifically performed on high barrier multilayer films of EVOH (32% ethylene)/polyethylene at 10 and 23 ° C and on moderate barrier monolithic films of nylon 6/6 at 15 and 23°C at humidities ranging from 0 to 100% R.H. permitting comparisons at two barrier levels and at differ ing temperatures. Details and critical issues of each method are presented and discussed. Measured barrier properties obtained with both methods of hu midification are compared. Conclusions on the effectiveness and application of the humidifying methods are presented. Additionally, because of their somewhat unusual behavior and high technical interest, the barrier properties of the two sample films and their dependence on humidity are specifically noted and discussed.
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