علوم و تکنولوژی پلیمر (Aug 2022)
Effect of Polyurethane Substrate Morphology on Gas Permeation Properties of Poly(dimethyl siloxane) Block Copolymer/Polyurethane Layered Membranes
Abstract
Hypothesis: Poly(dimethyl siloxane) block copolymers membranes are a good choice for gas separation application. The mechanical strength and gas separation properties of these polymers can be improved by the preparation of layered membranes. In layered membranes, the coating layer generally controls the flow and selectivity of gas, while the porous substrate plays the role of mechanical strength supplier. The dense layer, at the interface of the substrate and selective layer, can also affect the efficiency of the layered membranes gas separation, and its performance depends on the morphology of the substrate and the gas permeation properties of the substrate and the coating layer. The goal of this research is to prepare and investigate the effect of substrate morphology on the performance of poly(dimethyl siloxane) block copolymers/polyurethane layered membranes.Methods: Polyurethane substrates were prepared through the non-solvent-induced phase separation (NIPS) method. Different substrates with sponge-like and finger-like morphology structures were prepared with the help of changing the concentration of dope solution concentration (10, 20, 25, 30% by weight of polymer) and coagulation bath (molar ratio of water/methanol=100/0, 80/20, 70/30 and 50/50), and used for the preparation of poly(dimethyl siloxane) block copolymer/polyurethane layered membranes.Findings: The polyurethane substrates revealed a finger-like morphology structure when a water coagulation bath was used due to the high exchange rate of solvent/non-solvent. Meanwhile, by adding methanol to the coagulation bath, the morphology of the substrate changed to a sponge-like one. In an overview, the gas separation properties of poly(dimethyl siloxane) block copolymers were improved by using a polyurethane substrate. The results revealed that by changing the morphology of the substrate from finger-like to sponge-like, the CO2 permeability of the membranes improved from 1.58 GPU to 4.53 GPU. While the permselectivity of the layered membranes (CO2/N2) decreased from 21.94 to 12.57.
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