No abstract

Blends containing ionic liquid (IL) 1-ethyl-3-methyimidazolium tetrafluoroborate [emim][BF] gelled with Pebax 1657 block copolymers were modified by adding graphene oxide (GO) and fabricated in the form of thin film composite hollow fiber membranes. Their carbon dioxide (CO) separation performance was evaluated using CO and N gas permeation and low-pressure adsorption measurements, and the morphology of films was characterized using scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. Upon small addition of GO into the IL-dominated environment, the interaction between IL and GO facilitated the migration of IL to the surface while suppressing the interaction between IL and Pebax, which was confirmed using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Amplified migration of IL to the surface and better dispersion of GO stacks were further achieved under alkaline conditions. With the enriched IL on the surface, the gas permeation through the films at 0.5 wt % GO and approximately 80 wt % IL loading reached 1000 GPU for CO with their CO/N selectivity (up to 44) approaching that of pure IL.

Block copolymer materials have been considered as promising candidates to fabricate gas separation membranes. This microphase separation affects the polymer chain packing density and molecular separation efficiency. Here, we demonstrate a method to template microphase separation within a thin composite Pebax membrane, through the controllable self-assembly of one-dimensional halloysite nanotubes (HNTs) within the thin film via the solution-casting technique. Crystallization of the polyamide component is induced at the HNT surface, guiding subsequent crystal growth around the tubular structure. The resultant composite membrane possesses an ultrahigh selectivity (up to 290) for the CO/N gas pair, together with a moderate CO permeability (80.4 barrer), being the highest selectivity recorded for Pebax-based membranes, and it easily surpasses the Robeson upper bound. The templated microphase separation concept is further demonstrated with the nanocomposite hollow fiber gas separation membranes, showing its effectiveness of promoting gas selectivity.

The current methods used to impart flameretardant or fire-resistant properties to flexible polyurethane foams (PUFs) to meet fire safety requirements entail the use of halogenated phosphorus-based compounds. Whereas these are highly effective as flame retardants, the associated toxicity derived from halogens in the burning fumes are deadly. To address this problem, we herein present a facile and efficient method of fabricating highly fire-resistant flexible PUF using halogen-free nature-inspired coatings. All of the active ingredients used to fabricate the coatings originated from natural or widely available sources: chitosan from crustacean shells, acetic acid that is found in vinegar, and expandable graphite mined from mineral rocks, thus making this strategy environmentally friendly and sustainable. These coatings offer excellent flame-retardant properties; with a limiting oxygen index (LOI) value as high as 31%, the coated foam could potentially pass the highest levels within the British Standard 5852, which is a commonly accepted global industry standard for meeting the fire safety requirement of flexible PUF. Furthermore, cone calorimeter testing revealed the superior fire safety performance of the coated foam, including very low heat and smoke release upon burning. The flame retardancy of the coated PUFs is tunable depending on the amount of graphite employed in the coating solutions. It is anticipated that the coating strategy described here is applicable to other substrates.

Forward osmosis (FO) is an emerging low-energy technology. Much effort was given on developing a new membrane material and engineering membrane structure to improve the performance of FO membranes. The performances of two newly developed polyamide based thin film composite (TFC) FO membranes were tested and compared with the commercially available cellulose triacetate (CTA) FO membrane. The intrinsic properties of the two TFC FO membranes determined in RO experiments indicate superior performance of the membranes. When tested in FO experiments, TFC membranes delivered consistent results, confirming their outstanding permeability and selectivity properties. The study shows that future studies on membrane fouling will be necessary to have a better understanding of membrane performance and to further optimize membrane properties.