Microporous film containing water swellable fillers

摘要

A self-regulating breathable microporous film layer transmits water vapor at normal use conditions, and reduces or eliminates the vapor transmission when the vapor in the environment become excessive. The film layer includes a voided polymer matrix and a plurality of fine water-swellable filler particles disposed within the voids. When there is an excess of vapor, the filler particles swell to block or partially block transmission of vapor through the voids and the film layer.