Polyimide membranes plasticization

WI1 Wind, J.D., Sirard, S.M., Paul, D.R., Green, P.F., Johnston, K.P., and Koros, W.J. Carbon dioxide-induced plasticization of polyimide membranes pseudo-equilibrium relationships of diffusion, sorption, and swoliEovg, Macromolecules, 36,6433,2003. 

Figure 11.26. Initial decomposition temperature of polyimide membrane of different types and amounts of plasticizers. DGD — diethylene glycol dibenzoate, DMP — dimethyl phthalate. [Data from Totu E ...

Kanehashi, S., Nakagawa, T., Nagai, K., Duthie, X., Kentish, S. and Stevens, G. 2007. Effects of carbon dioxide-induced plasticization on the gas transport properties of glassy polyimides membranes. 298 147-155. 

Shao, L., Chung, T.-S., Goh, S.H. and Pramoda, K.P. 2005b. The effects of l,3-cyclohexanebis(methylamine) modification on gas transport and plasticization resistance of polyimide membranes. 267 78-89. 

J. D. Wind, C. Staudt-Bickel, D. R. Paul, W. J. Koros, Solid-state covalent cross-hnking of polyimide membranes for carbon dioxide plasticization reduction. Macromolecules, 36, 1882-1888 (2003). 

M. Alexis, W. Hillock, W. J. Koros, Cross-hnkable polyimide membrane for natural gas purification and carbon dioxide plasticization rednction. Macromolecules, 40, 583-587... 

Zeolite/polymer mixed-matrix membranes prepared from crosslinked polymers and surface-modified zeolite particles offered both outstanding separation properties and swelling resistance for some gas and vapor separations such as purification of natural gas. Hillock and coworkers reported that crosslinked mixed-matrix membranes prepared from modified SSZ-13 zeolite and 1,3-propane diol crosslinked polyimide (6FDA-DAM-DABA) synthesized from 2,2 -feis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, p-dimethylaminobenzylamine-and 3,5-diaminobenzoic acid displayed high CO2/CH4 selectivities of up to 47 Barrer and CO2 permeabilities of up to 89 Barrer under mixed gas testing conditions [71]. Additionally, these crosslinked mixed-matrix membranes were resistant to CO2 plasticization up to 450 psia (3100kPa). 

Specialty polymers achieve very high performance and find limited but critical use in aerospace composites, in electronic industries, as membranes for gas and liquid separations, as fire-retardant textile fabrics for firefighters and race-car drivers, and for biomedical applications (as sutures and surgical implants). The most important class of specialty plastics is polyimides. Other specialty polymers include polyetherimide, poly(amide-imide), polybismaleimides, ionic polymers, polyphosphazenes, poly(aryl ether ketones), polyarylates and related aromatic polyesters, and ultrahigh-molecular-weight polyethylene (Fig. 14.9). 

In case of ultrafiltration membranes, resistance of membrane is owing to membrane material. Therefore, selection of membrane material is the most important. Figure 9 shows comparison of engineering plastics which have ever investigated for ultrafiltration membranes with solvent and high temperature resistance. It is the most difficult to find materials which satisfy both excellent resistivity and excellent processibility. Polyimide is an only material commercialized for a rather resistant ultrafiltration membrane. 

Wind, J.D. et al.. The effects of crosslinking chemistry on COj plasticization of polyimide gas separation membranes. Industrial and Engineering Chemistry Research, 2002. 41(24) 6139-6148. 

In the past, the available membranes lost a significant fraction of their selectivity when operated at these high temperatures. They also became plasticized by absorbed heavy hydrocarbons in the feed gas. As a consequence, a number of early hydrogen-separation plants installed in refineries had reliability problems. The development of newer polyimide and polyaramide membranes that can safely operate at high temperatures has solved most of these problems and the market for membrane-based hydrogen-recovery processes in refineries is growing. 

Duthie X, Kentish S, Powell C, Nagai K, Qiao G, Stevens G. Operating temperature effects on the plasticization of polyimide gas separation membranes. J Membr Sci 2007 294(l-2) 40-9. 

Membrane technology has often been mentioned as the next technological generation for the prtrification of natural gases. Indeed, membrane systems are operated successfully for gas sweetening for decades. The best known examples include CO2 selective membranes that are based on pure polymers, e.g., cellulose acetate (Cynara membranes by Natco or Separex membranes by UOP) and polyimide (Ube). Despite their popularity, their performance at high pressures deteriorates as a result of CO2 induced plasticization. 

Kapantaidakis, G.C., Koops, G.H. and Wessling, M. 2003. CO2 plasticization of polyethersnl-fone/polyimide gas-separation membranes. 49 1702-1711. 

Krol, J.J., Boerrigter, M. and Koops, G.H. 2001. Polyimide hollow fiber gas separation membranes Preparation and the suppression of plasticization in propane/propylene environments. 184 275-286. 

Plasticization behaviour induced by condensable gases and vapours (e.g. carbon dioxide, hydrocarbons and other organic vapours) in polymer membranes is stiQ a painful problem in polymeric membrane-based gas separation applications [27,28]. Recently, novel hyperbranched polyimides were prepared from telechelic polyimides and an attempt was made to improve its gas separation performance and physical stability by obtaining plasticization-resistant materials [29-33] (see e.g. Chapters 4, 6 and 7 of this book). 

Thus, we can state that the use of hyperbranched polyimides can enhance the resistance to plasticization of polymer membranes. 

Section I (Novel Membrane Materials and Transport in Them) focuses on the most recent advances in development of new membrane materials and considers the transport parameters and free volume of polymeric and even inorganic membranes. Kanehashi et al. (Chapter 1) present a detailed review of hyperbranched polyimides, which are compared with more common cross-linked polyimides. These polymers with unusual architecture were studied in the hope that they would show weaker tendency to plasticization than conventional linear polymers. However, many representatives of this new class of polymers reveal relatively poor film forming properties due to absence of chain entanglement. Nonetheless, some promising results obtained can show directions of further studies. 

In EP07708077A3 (Dabou et al. 1996), gas separation polymer membranes were prepared from mixtures of a polysulfone, Udel P-1700 and an aromatic polyimide, Matrimid 5218. The two polymers were proven to be completely miscible as confirmed by optical microscopy, glass transition temperature values and spectroscopy analysis of the prepared mixtures. This complete miscibility allowed for the preparation of both symmetric and asymmetric blend membranes in any proportion from 1 to 99 wt% of polysulfone and polyimide. The blend membranes showed significant permeability improvements, compared to the pure polyimides, with a minor change in the selectivity. Blend membranes were also considerably more resistant to plasticization compared with pure polyimides. This work showed the use of polysulfone-polyimide polymer blends for the preparation of gas separation membranes for applications in the separation of industrial gases. 

H. Wang, T.-S. Chung, D.R. Paul, Physical aging and plasticization of thick and thin films of the thermally rearranged ortho-functional polyimide 6FDA-HAB, Journal of Membrane Science 458 (2014) 27-35. 

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