A Study of the Reinforcement Effect of MWCNTs onto Polyimide Flat Sheet Membranes

Abstract

Polyimides rank among the most heat-resistant polymers and find application in a variety of fields, including transportation, electronics, and membrane technology. The aim of this work is to study the structural, thermal, mechanical, and gas permeation properties of polyimide based nanocomposite membranes in flat sheet configuration. For this purpose, numerous advanced techniques such as atomic force microscopy (AFM), SEM, TEM, TGA, FT-IR, tensile strength, elongation test, and gas permeability measurements were carried out. In particular, BTDA–TDI/MDI (Ρ84) co-polyimide was used as the matrix of the studied membranes, whereas multi-wall carbon nanotubes were employed as filler material at concentrations of up to 5 wt.% All studied films were prepared by the dry-cast process resulting in non-porous films of about 30–50 μm of thickness. An optimum filler concentration of 2 wt.% was estimated. At this concentration, both thermal and mechanical properties of the prepared membranes were improved, and the highest gas permeability values were also obtained. Finally, gas permeability experiments were carried out at 25, 50, and 100 °C with seven different pure gases. The results revealed that the uniform carbon nanotubes dispersion lead to enhanced gas permeation properties.

Nanocarbon-Based Mixed Matrix Pebax-1657 Flat Sheet Membranes for CO2/CH4 Separation

“…By increasing the number of GNPs, the CO 2 permeability also increases, presenting a maximum value for the concentration of 3 and of 5.3 wt.% in the cases of oxidized and raw GNPs, respectively. This behavior is in correlation with what is reported in literature for Pebax [ 46 , 57 , 58 ] but also for other polymeric mixed matrix membranes [ 16 , 59 , 60 ]. Here, it must be noted that the addition of the oxidized GNPs finally provides improved properties and better position in the Robeson plot of selectivity versus permeability, as the selectivity is remaining constant, and simultaneously the CO 2 permeability increases about 46% at 1.3 bar.…”

Review: Mixed-Matrix Membranes with CNT for CO2 Separation Processes

“…For instance, in Reference [ 87 ] researchers found better results by adding to a brominated poly (2,6-diphenyl-1,4-phenylene oxide) (BPPOdp) membrane 9 wt% of SWCNT and 5 wt% of MWCNT. Another investigation [ 88 ] demonstrated a better permeability by adding only 2 wt% of MWNT to a N-methyl-2-pyrrolidone membrane (at higher quantities of MWNT the membranes deteriorates due to the formation of agglomerates); the authors attributed this performance to the effective dispersion of the nanotubes in the polymer. The addition of carbon nanotubes to the polyimide membranes matrices improves their properties due to the uniform dispersion achievement of the nanotubes in the polymer matrix, which could play the role of a polymeric-chain crosslinker.…”