Special problems and methods in the study of water vapor transport in polymers

Water presents special and unique difficulties in diffusion and sorption measurements because of its high cohesive energy and hydrogen-bonding capacity. In the case of transport measurements in hydrophilic polymers the time-lag method is complicated by the tendency of the water vapor to be adsorbed onto the glass receiving sections of the equipment. On the other hand, with more hydrophilic polymers where nonsteady-state direct sorption methods can be used the large amount of heat liberated during the sorption process again causes considerable difficulty. A discussion of these and other problems concerned with transport studies with water vapor is presented and various practical solutions are offered.