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. Activation energy for permeation depends on the amount of layered silicate in polyimide coatings. • Freeze-drying of layered silicates is a key step to enhance the barrier properties in coatings with organic solvent • A higher proportion of layered silicates leads to an increase in elongation of the tortuous path and a reduction in permeation • Activation energies of the permeation of water and oxygen show differences in the permeation mechanisms of the investigated gases