Abstract
A fluid penetration technique is described which enables measurements to be made of penetration rate into coatings, of total pore volume, and of the subsequent permeation rate of fluid through the film. From these measurements, the number of pores and their length and diameter can be calculated assuming a simple model of pore structure. The lengths of pores calculated in this way are shown to be unrealistically large and a more complex model structure is postulated involving large and small pores serially connected. In order to determine pore sizes for this model it is necessary to generate an additional equation and this is achieved by measuring air permeation through the film. Pore sizes determined in this way are comparable in magnitude with those measured by other techniques.
Evidence is offered which suggests that air flow through coatings is molecular rather than viscous and that fluid pressures within the coating pore structure can be negative.
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