Temperature dependence of gas barrier property of clay-polymer composite coatings

The temperature dependence of the coating layer`s He gas permeability was measured using a coat made of natural smectite and water-soluble nylon. When the smectite content was 100%, the temperature dependence was minimal, but it increased as the polymer content increased. Temperature dependence was used to calculate the activation energy of He gas permeation. When the coating layer was made entirely of clay, the activation energy of He gas permeation was the lowest, and it increased as the polymer component increased. When the polymer content was 60 vol%, the activation energy was the same as that of the polymer alone, and it leveled off thereafter. From this result, the gas permeation mechanism was discussed. When the polymer content is <60 vol%, the movement of the polymer filled in the spaces between the smectite platelets is restricted by the smectite platelets. At 60 vol% polymer content, the gas permeation through the polymer can be regarded similar to that through a pristine polymer, whose motion is not constrained by the clay. Due to the maze effect of the filler with a high aspect ratio of up to 350, the absolute value of gas permeability of the composite film was reduced by three orders of magnitude compared to the film made of polymer alone.