Permeation mechanism of gas molecules through polyimide barrier coatings with freeze- and oven-dried modified layered silicates

One effective strategy to improve the barrier performance of polymeric coating layers is the incorporation of layered silicate particles. This study investigates how the drying technology of silicates - specifically freeze drying versus oven-drying - affects the permeation properties of the coatings. Modified layered silicates, prepared using both drying methods, are incorporated in varying amounts into polyimide coatings. The arrangement, orientation, and exfoliation of the particles are analysed using SEM. Results indicate that a higher proportion of layered silicates enhances the tortuosity of the diffusion pathway, thereby reducing permeability. Furthermore, permeation measurements of oxygen and water vapor, along with the calculated activation energies, reveal distinct differences in the permeation mechanisms of these gases through the coating films, highlighting the significant impact of the drying method on the barrier properties of the coatings.