Barrier coating of an elastomer and a dispersed layered filler in a liquid carrier, and coating compositions, particularly for tires

An aqueous barrier coating mixture comprises (a) an elastomeric polymer; (b) a dispersed exfoliated layered filler having an aspect ratio greater than 25, and (c) at least one surfactant, wherein the solids content of said mixture is between 1% and 30% and the ratio of polymer (a) to filler (b) is between 20: 1 and 1.2:1; and wherein upon applying to a substrate and allowing said mixture to dry to a flexible barrier coating having the same ratio of polymer to filler as in said solution, a coating is formed which provides an at least 10-fold greater reduction in gas permeability than a coating formed of said unfilled polymer (a) alone.