Additional comments on a novel technique for the quantitative measurement of gaseous uptake in organic polymers at high pressure

The decrease in the normalised frequency of a vibrating slender elastic cantilever with an absorbing polymer attached at its free end is proportional to the combined sorbed gas mass and entrained mass. To a good approximation the entrained mass contribution arises from two factors: the ambient gas density and the increase in the specimen compression area. The latter factor may increase if the polymer swells during sorption and this process can significantly increase the entrained mass contribution. An appropriate correction is required. The authors describe how this may be achieved and provide sample results for a silicone elastomer sorbing CO₂ at high gas pressures.