Gas Transport Phenomena in PDMS/Matrimid Thin Film Composite Membrane

Membrane-based separation plays a vital role in various industrial sectors, facilitating the effective partitioning of mixture components at low energy and capital costs. The efficacy of this separation is largely determined by the membrane materials and their interactions with the mixture components. Polydimethylsiloxane (PDMS) membrane, a silicon-based organic polymer, is notable for its gas separation capabilities due to its high permeability and appreciable gas selectivity. Beyond its gas separation attributes, PDMS offers additional advantages including thermal stability, mechanical flexibility, and potential for hybridization with other materials, making it a versatile choice for numerous separation applications. In practical scenarios, PDMS membranes are often designed as thin film composites (TFCs). This configuration comprises a thin PDMS selective layer cast on a porous support, which ensures membrane integrity under high feed pressures while maintaining a desirable flux. Most transport models in reverse osmosis, for membranes designed as TFCs, assume negligible resistance within the support. This study helps validate such assumptions by evaluating the pore sizes of Matrimid supports and their contributions to gas flux. PDMS was spin-coated on Matrimid supports, followed by gas permeation experiments to measure the gas permeances of N2, He, and CO2 through the membranes. The acquired data were utilized in a permeation resistance model, developed to evaluate the surface porosity and pore sizes of both the PDMS layer and the Matrimid support. Understanding such transport resistance within the support aids in designing support materials with optimal pore sizes for defect-free, high-flux membranes. This insight is pivotal for optimizing PDMS membranes for enhanced separation efficiency and providing a foundation for further explorations into innovative membrane designs, particularly in CO2 capture applications.