Surface roughness, poly silicon layers

Asymmetric blend poly(ether sulfone)-polyimide (PES-PI) hollow fiber membranes were prepared at different air gaps and used for gas separation [23,24]. It was observed that the permeance of CO2 and N2 increased with an increase in air gap while the ideal selectivity decreased when the hollow fibers were uncoated. After silicone coating, no significant change was observed either in permeance or in the permeance ratio. Although the feed gas was supplied to the shell side of the hollow fiber, it seems that the skin layer is on the lumen side when the SEM pictures are examined. From AFM [25], it was observed that the mean roughness parameter of the inner surface (uncoated lumen side) increased with an increase in the air gap. 

Many technical textiles are finished with a heavy polymeric coating of, e.g., poly(vinyl chloride) (PVC), polyurethane, or silicone, which effectively masks the textile fabric with a smooth surface. One exemplary application of coated textiles, where easy or self-attained cleanability is highly required, is the construction of textile roofs in modem architecture. The present solution to decrease dirt take-up is to apply hydrophobic topcoats, i.e. layers of lacquer of approx. 5 jm thickness, to the coated fabrics. However, the performance of these conventional topcoats with regard to cleanability is not sufficient. The approaches to the creation of superhydrophobic surfaces by means of micro-rough surfaces as discussed in Section 6.1 refer to the texture of textile fabrics as well as the actual fiber surfaces, and are not necessarily applicable to coated textiles. 

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