Effect of alternating humidity and dryness on the durability of adsorbent sheets used in open cycle adsorption processes

Silica gel based composite materials are considered as promising materials in open-cycle adsorption processes for water vapor adsorption/desorption. However, their long-term performance under fluctuating humidity conditions remains unclear. This study investigates the role of alternating humid and dry aging cycles on the mechanical and water vapor adsorption properties of silica gel-polymer matrix composite sheets. Controlled humid/dry cycles mimicking real operating conditions were applied to the sheets, followed by tensile strength and water vapor adsorption tests to assess performance degradation. The aim was to understand how these cycles affect the sheets' ability to capture and release water vapor effectively over time. The findings show the material's good hydrothermal stability, maintaining mechanical strength and water vapor adsorption after aging. The 50–100–0 samples had the lowest performance post-aging (average strength and modulus of 1.13 MPa and 26.8 MPa, respectively). Critical conditions occur in long aging cycles, such as 40–1000 and 50–1000 batches, leading to substantial performance decline post-drying, hinting at slight permanent damage. The 50–1000 batch showed a tensile modulus of 34.8 MPa after 7 days of dry storage, about 18.8 % less than unaged samples. This information serves as a preliminary approach for optimizing the material design of these sheets for open-cycle adsorption applications. By identifying potential weaknesses arising from humidity cycling, the study paves the way for improvements that ensure long-term effectiveness and reliability in these systems.