Permeability and conductivity of platelet-reinforced membranes and composites

We present large scale simulations of the diffusion constant $D$ of a random composite consisting of aligned platelets with aspect ratio $a/b>>1$ in a matrix (with diffusion constant $D_0$) and find that $D/D_0 = 1/(1+ c_1 x + c_2 x^2)$, where $x= a v_f/b$ and $v_f$ is the platelet volume fraction. We demonstrate that for large aspect ratio platelets the pair term ($x^2$) dominates suggesting large property enhancements for these materials. However a small amount of face-to-face ordering of the platelets markedly degrades the efficiency of platelet reinforcement.Comment: RevTeX, 5 pages, 4 figures, submitted to PR

Diffusion Mass Tranfer In fluid Systems

xviii, 580 hal.; ill.; 23c

Ammonia selective hollow fibers

Microporous polypropylene hollow fibers can be coated with a 1.9 μm layer of perfluorosulfonic acid polymer (‘Nafion’), to give membranes selective for ammonia. The permeability, of the order of 104 barrers, is comparable with that obtained previously for thick flat perfluorosulfonic acid membranes, though the permeance is much higher. The selectivity for ammonia over hydrogen can be as high as 500:1 at room temperature; it is much higher for ammonia over nitrogen. This selectivity drops as the temperature rises. These composite membranes will be commercially valuable if they can be made to withstand the high pressures characteristic of ammonia synthesi