Flake-filled reactive membranes

Aligned mica flakes and colloidal zinc oxide can combine to reduce the acid permeability and increase the lag time in polyvinylalcohol (PVA) membranes. The permeability is reduced up to 10 times by the flakes, but is affected much less by the zinc oxide. The lag times are increased by up to 1000 times by a combination of flakes and reaction. The results can be estimated with theories for this transport, including variations with the square of the volume fraction of flakes and the first power of the zinc oxide concentration. These estimates are successful only when the flakes are evenly distributed within the membrane. When they are unevenly distributed, the apparent membrane permeability behaves differently. While the experiments use only polyvinylalcohol as a polymer, the same flakes and reactants will give the same relative permeability reductions with other, less permeable polymers, (C) 2002 Elsevier Science B.V. All rights reserved.