Suppression of CO2-plasticization by semiinterpenetrating polymer network formation

✍ Scribed by A. Bos; I. G. M. Pünt; M. Wessling; H. Strathmann

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 230 KB
• Volume: 36
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(19980715)36:9<1547::aid-polb12>3.0.co;2-5

✦ Synopsis

CO 2 -induced plasticization may significantly spoil the membrane performance in high-pressure CO 2 /CH 4 separations. The polymer matrix swells upon sorption of CO 2 , which accelerates the permeation of CH 4 . The polymer membrane looses its selectivity. To make membranes attractive for, for example, natural gas upgrading, plasticization should be minimized. In this article we study a polymer membrane stabilization by a semiinterpenetrating polymer network (s-ipn) formation. For this purpose, the polyimide Matrimid 5218 is blended with the oligomer Thermid FA-700 and subsequently heat treated at 265ЊC. Homogeneous films are prepared with different Matrimid/Thermid ratios and different curing times. The stability of the modified membrane is tested with permeation experiments with pure CO 2 as well as CO 2 /CH 4 gas mixtures. The original membrane shows a minimum in its permeability vs. pressure curves, but the modified membranes do not indicating suppressed plasticization. Membrane performances for CO 2 /CH 4 gas mixtures showed that the plasticizing effect indeed accelerates the permeation of methane. The modified membrane clearly shows suppression of the undesired methane acceleration. It was also found that just blending Matrimid and Thermid was not sufficient to suppress plasticization. The subsequent heat treatment that results in the s-ipn was necessary to obtain a stabilized permeability.