Effects of Thermal Treatment and Physical Aging on the Gas Transport Properties in Matrimid^®

Abstract

-Carbon dioxide and methane transport in a commercial polyimide, Matrimid 5218 Ò , has been characterized in order to evaluate the effect of membrane thermal treatment and physical aging on its potentialities for CO 2 /CH 4 separation. In particular, CO 2 and CH 4 permeabilities and diffusion coefficients were measured at three different temperatures (35, 45 and 55°C) in films pretreated at 50, 100, 150 and 200°C, respectively. The performances of each sample were examined for a period of more than 3 000 hours. Permeability and diffusivity values for both penetrants showed a marked decrease with increasing the pretreatment temperature up to 150°C and remained, then, substantially unchanged for specimens pretreated at the highest temperature. Interestingly, the samples characterized by the higher flux after film formation also showed a faster aging phenomenon, leading to a 25% decrease of CO 2 permeability in the period inspected. Conversely, the samples pretreated at temperatures of 150°C, or higher, displayed very stable transport properties for the entire duration of the monitoring campaign. At the end of the aging period considered, the differences among samples were definitely reduced, suggesting that the initial behaviors are related to different polymer structures induced by pretreatment, which slowly evolve in time towards more similar and more stable configurations. Such aging rearrangements affect both CO 2 and CH 4 permeability in a similar way, so that no significant changes were observed for selectivity, which showed only a slight increment by increasing the temperature of the thermal treatment or the duration of the aging period. 150°C ont affiche´des proprie´te´s de transport tre`s stables pendant toute la dure´e des mesures. Par conse´quent, a`la fin de l'e´tude, les diffe´rences entre les e´chantillons ont e´te´nettement re´duites, ce qui sugge`re que la structure initiale pourrait eˆtre due a`des structures polyme´riques diffe´rentes, induites par un pre´traitement, qui e´voluent lentement avec le temps vers des configurations plus semblables et plus stables. Il est important de remarquer qu'un tel re´arrangement a affected e la meˆme manie`re la perme´abilite´au CO 2 et celle au CH 4 . Nous n'observons donc pas de changements significatifs en ce qui concerne la se´lectivite´qui a montre´seulement une le´ge`re hausse lorsque l'on augmente la tempe´rature du traitement thermique ou le temps de vieillissement.

Effect of relative humidity and temperature on gas transport in Matrimid®: Experimental study and modeling

“…As often showed by many authors, the polymer thermal history can significantly affect the mass transport properties, as well as the performance of glassy polymer membranes [7,9,40]. However, it was observed that the pretreatment of Matrimid s films at 200 1C is able to produce membranes with gas transport properties stable for a period of at least 6 months, as no significant aging was detected from gas permeability measurements [41]. Density measurements have been carried out on Matrimid s samples after the thermal pretreatment, by means of the buoyancy method (Sartorius Density Kit YDK01), weighing the specimens in air and in n-dodecane (Sigma-Aldrich, anhydrous, Z99% purity).…”

Effect of relative humidity and temperature on the gas transport properties of 6FDA–6FpDA polyimide: Experimental study and modelling

“…the protocol used for preparation [6], the exposition to swelling agents [11], [12] or thermal treatments [13]- [15].…”

“…vacuum at 200°C for 24 h prior to testing in order to ensure solvent and low molecular weight species removal, as well as to give stability to the membrane properties, because such pre-treatment ensures the absence of aging phenomena, that cause permeability to change with time, as proven in the case of Matrimid [13]. …”

Impact of coated calcium carbonate nanofillers and annealing treatments on the microstructure and gas barrier properties of poly(lactide) based nanocomposite films

“…Although it is commonly acknowledged that gas transport properties of polymers are highly dependent on the polymer amorphous or semicrystalline microstructure, their relation with physical ageing has been much less studied. The importance of this parameter on gas transport properties has been mainly investigated on amorphous thin films usually prepared by solvent cast process from polymers with high glass transition temperature . The gas permeability of these films has been shown to change in time, due to a slow reorganization of the polymer chains from a nonequilibrium thermodynamical state to an equilibrium state, leading to a redistribution of the free volume sizes and contents.…”

“…The importance of this parameter on gas transport properties has been mainly investigated on amorphous thin films usually prepared by solvent cast process from polymers with high glass transition temperature. [20][21][22] The gas permeability of these films has been shown to change in time, due to a slow reorganization of the polymer chains from a nonequilibrium thermodynamical state to an equilibrium state, leading to a redistribution of the free volume sizes and contents. Film forming processes based on melt routes usually involve high cooling rates that can also lead to immobilize polymer chains in a non-equilibrium state.…”