Standard Scope
Test methods for determining maximum pore size and pore size distribution in membrane laminates measure gas displacement pressures through liquid-saturated porous media. Designed specifically for porous materials, ASTM F316 defines standardized procedures for identifying the largest effective pore diameter and mean flow pore diameter in technical textiles, nonwoven filter fabrics, protective apparel membranes and microporous barrier laminates. The standard covers bubble point and mean flow pore determinations using automated or manual gas flow instrumentation, but excludes non-porous solid films or woven fabrics with visible open apertures.
Measurement Principle
Liquid displacement relies on wetting a porous textile sample with a fluid of known surface tension until every capillary path is filled. Increasing gas pressure applied to one side of the saturated material systematically forces fluid out of the largest pores first, triggering initial gas flow recorded as the bubble point pressure. Further pressure increases flush progressively smaller capillaries, allowing full calculation of cumulative gas flow curves compared against dry sample flow profiles.
Pore Evaluation
Mean flow pore size represents the precise aperture diameter at which half of the total gas flow passes through the wetted structure. This metric determines filtration efficiency ratings and liquid barrier thresholds in protective apparel fabrics.
Verification Requirement
Quality control laboratories verify test fluid purity and temperature stability during testing procedures. Mill test certificates must declare the specific wetting liquid used, applied gas pressure ramp rate and resulting mean flow pore distribution metrics.
