Water vapor permeable polyurethane films based on the hyperbranched aminoethers of boric acid

Recent advancements in polyurethane-based membranes for gas separation

Gas separation membranes are critical in a variety of environmental research and industrial applications. These membranes are designed to selectively allow some gases to flow while blocking others, allowing for the separation and purification of gases for a variety of applications. Therefore, the demand for fast and energy-efficient gas separation techniques is of central interest for many chemical and energy production diligences due to the intensified levels of greenhouse and industrial gases. This encourages the researchers to innovate techniques for capturing and separating these gases, including membrane separation techniques. Polymeric membranes play a significant role in gas separations by capturing gases from the fuel combustion process, purifying chemical raw material used for plastic production, and isolating pure and noncombustible gases. Polyurethane-based membrane technology offers an excellent knack for gas separation applications and has also been considered more energy-efficient than conventional phase change separation methodologies. This review article reveals a thorough delineation of the current developments and efforts made for PU membranes. It further explains its uses for the separation of valuable gases such as carbon dioxide (CO2), hydrogen (H2), nitrogen (N2), methane (CH4), or a mixture of gases from a variety of gas spillages. Polyurethane (PU) is an excellent choice of material and a leading candidate for producing gas-separating membranes because of its outstanding chemical chemistry, good mechanical abilities, higher permeability, and variable microstructure. The presence of PU improves several characteristics of gas-separating membranes. Selectivity and separation efficiency of PU-centered membranes are enhanced through modifications such as blending with other polymers, use of nanoparticles (silica, metal oxides, alumina, zeolite), and interpenetrating polymer networks (IPNs) formation. This manuscript critically analyzes the various gas transport methods and selection criteria for the fabrication of PU membranes. It also covers the challenges facing the development of PU-membrane-based separation procedures.

Molecular Simulation of Pervaporation on Polyurethane Membranes

This article discusses a molecular simulation of membrane processes for the separation of liquid mixtures during pervaporation. A method for simulating the structure of polyurethane membranes was developed. The method was based on the known mechanisms of the formation of macromolecules from constituent monomers. For the formation of a chemical bond between the monomers, values of the parameters of the potentials of intermolecular interactions were set so that bonds were formed only between the corresponding atoms. The algorithm was validated to produce polymer films from diphenylmethane diisocyanate (MDI) and amino ethers of boric acid (AEBA). The polymer film obtained according to the developed algorithm was used to study the adsorption of ethanol and water. The concentration distributions of the components inside the polymer film were obtained for films of various thicknesses. Modifications of the DCV-GCMD method were proposed for the molecular simulation of pervaporation. The algorithm was based on maintaining a constant density of the mixture in the control volume. After the molecules were added to the control volume, thermodynamic equilibrium was established. During this process, molecules moved only in the control volume, while the rest of the molecules were fixed. The proposed algorithm was used to calculate the flows of water and ethanol through the polymer film.

Organophosphorus Polyurethane Ionomers as Water Vapor Permeable and Pervaporation Membranes

Organophosphorus polyurethane ionomers (AEPA-PU) based on aminoethers of ortho-phosphoric acid (AEPA) were obtained and studied as pervaporation membrane materials for separating isopropanol/water mixtures. The regularities of the change in the water vapor permeability of AEPA-PU were also investigated. It has been established that an increase of solute content in the composition of the urethane-forming system and the content of ionogenic groups in AEPA leads to a noticeable increase in the vapor permeability of the resulting film materials. An increase in water vapor permeability values is accompanied by a significant increase in the pervaporation characteristics of AEPU-PU. It was shown that the conditions promoting clustering of phosphate anions cause an increase in the values of the vapor permeability coefficient of AEPA-PU obtained using polyoxypropylene glycol. However, the hydrophobicity of the polypropylene glycol surrounding the clusters makes it difficult for water to move through the polymer matrix. Due to the hydrophilicity of polyoxyethylene glycol, the highest values of water vapor permeability and pervaporation characteristics are achieved for AEPA-PU synthesized using PEG.

Organoboron Ionic Liquids as Extractants for Distillation Process of Binary Ethanol + Water Mixtures

Aminoethers of boric acid, which are organoboron ionic liquids, were synthesized by using boric acid, triethanolamine, and triethylene glycol/diethylene glycol. Due to the formation of intermolecular complexes of borates, the structure of aminoethers of boric acid contains ion pairs separated in space, giving these compounds the properties inherent to ionic liquids. It is established that the thermal stability of aminoethers under normal atmospheric conditions increases with an increase in the size of the glycol. According to measurements of fast scanning calorimetry, density, dynamic viscosity, and electrical conductivity, water is involved in the structural organization of aminoethers of boric acid. The impact of the most thermostable organoboron ionic liquids on the phase equilibrium conditions of the vapor–liquid azeotropic ethanol–water mixture is studied. It is shown that the presence of these substances leads to increase in the relative volatility of ethanol. In general, the magnitude of this effect is at the level shown by imidazole ionic liquids, which provide high selectivity in the separation of aqueous alcohol solutions. A large separation factor, high resistance to thermal oxidative degradation processes, accompanied by low cost start reagents, make aminoethers of boric acid on the basis of triethylene glycol a potentially effective extractant for the extractive distillation of water–alcohol mixtures.