MFI-type zeolite dispersed in rubbery polymers: influence on surface and transport properties
Advancing the chemical engineering fundamentals
Membranes and Membrane Science (T2-8P)
Keywords: Gas separation, mixed matrix membrane, rubbery polymers, zeolite
The combination of organic and inorganic phases by means of the dispersion of a filler in a polymer matrix is an interesting route to modify the physical and transport properties of various materials [1, 2]. Adhesion problems can represent a significant limit in the development of mixed matrix membranes based on glassy polymers, which are widely used for separations on industrial scale. On the contrary the performance of the rubbers, in principle less appropriate to achieve remarkable separation factors, can be favourably improved via adequate inorganic fillers without defects at the interfacie polymer-crystal. In this framework the effect of MFI-type filler, a zeolite with sinusoidal and straight channels of a nominal pore size of about 0.55 nm, dispersed into different rubbery polymers has been investigated.
Water contact angle measurements, carried out in static and dynamic methods, showed an increase of the hydrophobic character of the hybrid samples as a function of the zeolite content for all polymer matrices. However, significant differences between bottom and upper (exposed to air) membrane sides have been observed due to the specific orientation of the terminal –OH groups of the zeolite during the membrane formation.
Microscopic investigations showed as the membrane morphology and the zeolite distribution within the polymer matrix are strongly affected by the filler concentration.
For what concerns the transport properties the presence of the zeolite filler can determine, according to a different behaviour of permanent gases at temperature changes, the inversion of the permeation rate order of some species with respect to the original polymer. In fact, the permeability of the more condensable gases, characterised by a big kinetic diameter and also by a significant solubility value, results more affected by the zeolite presence due to molecular sieving prevailing on the surface adsorption mechanism. Nevertheless, this trend becomes less important as operating temperature rises.
[1] T.T. Moore, R. Mahajan, D.Q. Vu, W.J. Koros, AIChE J., 50(2), 2004, 311.
[2] G. Clarizia, C. Algieri, E. Drioli, Polymer, 45, 2004, 5671.
Presented Tuesday 18, 13:30 to 15:00, in session Membranes and Membrane Science (T2-8P).
