Microcomposite membranes

There are dear technological incentives for generating novel microcomposite membranes based on perfluorinated ionomer matrices. To begin with, the remarkable chemical inertness and high temperature stability of the base polymer would allow applications in a range of environments... 

In a practical vein it was observed that the structural integrity of the microcomposite membranes (from methanol solvent) is very poor after about 45 min. teeatment in that the films are susceptible to brittle fracture within the context of simple handling. In fact, sarnies having an immersion time of 60 min. (88 wt%) can be easily crumbled which is an interesting feet when compared with the conventional experience of Nafion behaving as an extremely cohesive material. 

Figure 3. Tensile stress vs. strain for Nafion microcomposite membranes having indicated silicon oxide solids uptakes from TEOS/methanol solutions.

In a similar vein, Sakai, Takenaka and Torikai produced Nafion/metal microcomposites by reducing palladium, rhodium, platinum and silver ion-exchanged membranes with H, at high temperatures (100-300°C) (26). The affected metal clusters, distributed homogeneously, were about 50 A in size. As in Risen s work, a polymer matrix template effect appears to be operative. These systems were considered and evaluated within the context of gas separations technology. 

Figure 8. FT-IR (ATR) difference spectra of Nafion/silicon oxide microcomposites produced by immersion of hydrated membranes in TEOS/methanol solutions for the indicated times.

Yold has determined by IR spectroscopy that the degree of silicon oxide network connectivity increases with increasing H O/TEOS mole ratio for add-catalyzed polymerizations in bulk solutions (21). These results, if applicable to the membrane in situ add-catalyzed polymerizations described herein, serve to reinforce our conclusion that a more highly-coordinated silicon oxide structure exists within microcomposites produced with short immersion times according to procedure A, or according to the slow stepwise TEOS addition in procedure B. In either case, more initial hydrolysis water molecules per alkoxide molecule are available to promote this situation. General Conclusions... 

The diffusion of some aromatic solvents (benzene, toluene, and p-xylene) through microcomposites of NR/carboxylated styrene-butadiene rubber (XSBR) latex blend membranes (70/30) was investigated by Stephen et al. Results indicated that the blend membrane exhibited unexpected diffusion behaviour, and this was attributed to the immiscibility of the two blend... 

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