Partially pyrolized gas-separation membranes made from blends of copolyetherimides and polyimides

Elucidating the effect of chain extenders substituted by aliphatic side chains on morphology and gas separation of polyurethanes

“…Plasticization and penetrant competition can lead to reduced mixed-gas selectivity compared to single gas measurement [74][75][76]. Enhanced gas permeability along with significant reduced selectivity defines the plasticization [77,78]. It is evident from Figs.…”

Gas separation membranes obtained by partial pyrolysis of polyimides exhibiting polyethylene oxide moieties

“…12. For the sake of comparison, the data for cross-linked membranes were compared to those of PI0-based analogous ones, which were reported in a previous work [49], and of their pristine PI10 and PI0. Because the composition of the precursor membranes (i.e., before the thermal treatment) were similar in both PI10-and PI0-series, analogous acronyms will be used to indicate them.…”

“…In a recent study [49], our group developed a strategy that consisted in blending a high-free volume aromatic polyimide with block aromatic-aliphatic copolymers, which derived from the same aromatic polyimide but with poly(ethylene oxide) (PEO) moieties incorporated to the main chain. 6FDA-6FpDA polyimide was chosen as the aromatic polymer because of its high free volume, good mechanical resistance and good permeability/selectivity balance for CO 2 /CH 4 gas pair; however, this material suffers from plasticization.…”

Aromatic Polyimide Membranes with <em>Tert</em>-Butyl and Carboxylic Side Groups for Gas Separation Applications. Covalent Crosslinking Study

“…-Thermal crosslinking [33,[43][44][45], where the materials are subjected to elevated temperatures, generally above 300 °C and sometimes up to values close to 400 °C, that is, at temperatures above the Tg, so that intermolecular reactions occur between various groups of the polymer chain. In this type of crosslinking it is difficult to know whether small degradations also occur due to the high temperatures used and/or the high residence times at these temperatures [44,[46][47][48][49]. In fact, some researchers have used this partial degradation process as an advantage, since partially pyrolyzed membranes (PPMs), because removal of thermolabile groups, present in the macromolecular chain, translated in materials having good gas separation properties [50,51] However, this method has the disadvantage that a loss in mechanical properties was observed due to partial degradation of the macromolecular structure [47].…”