COLL 459 |
| Benny D. Freeman, Department of Chemical Engineering, Department of Chemical Engineering, University of Texas at Austin, 10100 Burnet Road, Austin, TX 78758 |
| Traditionally, incorporation of fine filler particles into polymer matrices reduces gas and vapor solubility and diffusivity, which, in turn, reduces permeability and has little or no effect on selectivity. Surprisingly, we have found that incorporation of very small fumed silica particles (of the order of several nm to several tens of nanometers in extent) into stiff chain glassy polymers (such as poly(4-methyl-2-pentyne) [PMP] actually increases permeability coefficients by as much as 300% and can double selectivity for separations such as the removal of butane from mixtures with methane. Positron annihilation lifetime spectroscopy data indicate that the fumed silica particles introduce extra free volume sites into the polymer matrix, which significantly increases diffusion coefficients (and, therefore, permeability) and weakens the size sieving nature of the polymer matrix, which increases selectivity. Activation energy of permeation and diffusion are consistent with this interpretation. The effect of particle size and polymer matrix type and permeability on this unusual behavior will also be discussed. |
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ACS Award in Colloid and Surface Chemistry Symposium Honoring Clay Radke
Division of Colloid and Surface Chemistry |