Effects of Using Different Polymers in Post-Synthesis Treatments of Zeolite a Coatings

Zeolite A coatings were prepared by the substrate heating and repeated conventional syntheses methods, targeting their use especially in adsorption heat pump applications. The coatings, grown on stainless steel, were then covered by polyvinyl acetate, polyvinyl alcohol, and cellulose acetate as post-synthesis treatments for improving the stabilities of the coatings. The water desorption properties of the metal-zeolite-polymer integrated systems were investigated by thermogravimetry (TG). Their stabilities were determined by the application of consecutive ultrasonic treatments and heating/cooling cycles. The zeolite coatings prepared by substrate heating contained void fractions of about 45%, significantly higher values than those obtained by repeated syntheses, which remained below 10%. When the former coatings were covered by polymer, they exhibited water desorption of about 0.13–0.15 g/g sample which was higher than the amount of water desorbed from both pure zeolite (0.12–0.14 g/g sample) and pure polymer (0.038–0.083 g/g sample) under the conditions investigated. Such behavior was absent for the more compact zeolite coatings prepared by repeated syntheses. This might signify that the zeolite coatings with larger intercrystalline void regions provided higher amount of surface and/or interactions between the polymer and zeolite phases, which mostly favored water desorption properties of composite coatings. Zeolite coatings prepared by both synthesis methods exhibited high stabilities after the post-synthesis treatments applied.