Results in Materials (Mar 2022)
Functionalized nanodiamonds in polyurethane mixed matrix membranes for carbon dioxide separation
Abstract
The present study demonstrated the incorporation of functionalized nanodiamonds (NDs) in polyurethane (PU) with various loadings (0.1, 0.25, 0.5, 0.75, and 1.0 wt%) to fabricate mixed matrix membranes (MMMs) with an upgraded capability of capturing CO2. An appropriate molar ratio of polyol:diisocyanate:chain extender (1:3:2) was used to synthesize all polymers. The MMMs were fabricated using the solution blending and casting method. The transmission electron microscopy results demonstrated that the silanized nanodiamond (SND) had less aggregation and a higher dispersity than the carboxylated nanodiamond. Also, by adding –NCO functional groups to the SND nanoparticles, their aggregation was minimized while the dispersity was improved. Moreover, characterization of the functionalized NDs was carried out by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The distribution of functionalized NDs throughout the PU matrix was confirmed by Field-emission scanning electron microscopy (FE-SEM). Also, the crystallinity of all the membranes was examined by XRD and differential scanning calorimetry; besides, we used FTIR to examine phase separation between soft and hard segments. Permeation tests of CO2, N2, and CH4 were performed on all membranes in order to examine CO2 separation performance. According to the gas permeability results, among all samples, PU/SND-NCO with 0.5 wt% SND-NCO showed the highest separation performance due to the better dispersion and interfacial interaction of fillers through the polymer matrix compared to other samples, as FE-SEM suggested earlier. Indeed, increasing SND-NCO up to 0.5 wt% caused an increment of 41.6, 37.0, and 53.6% for CO2 permeability, CO2/N2 selectivity, and CO2/CH4 selectivity, respectively, in comparison with the pure PU membrane.
