The present disclosure provides methods for forming asymmetric membranes. More specifically, methods are provided for applying a polymerizable species to a porous substrate for forming a coated porous substrate. The coated porous substrate is exposed to an ultraviolet radiation source having a peak emission wavelength less than 340 nm to polymerize the polymerizable species forming a polymerized material retained within the porous substrate so that the concentration of polymerized material is greater at the first major surface than at the second major surface.

The present disclosure provides methods for forming asymmetric membranes. More specifically, methods are provided for applying a polymerizable species to a porous substrate for forming a coated porous substrate. The coated porous substrate is exposed to an ultraviolet radiation source having a peak emission wavelength less than 340 nm to polymerize the polymerizable species forming a polymerized material retained within the porous substrate so that the concentration of polymerized material is greater at the first major surface than at the second major surface.

The present invention relates to a method for producing a porous membrane, the method being characterized in that a solvent system comprising 2-pyrrolidone and N-alkyl-2-pyrrolidone is used, wherein the content ratio of 2-pyrrolidone to N-alkyl-2-pyrrolidone in the solvent system is from 90%:10% to 10%:90%, based on mass %, and wherein N-alkyl-2-pyrrolidone is N-propyl-2-pyrrolidone and/or N-butyl-2-pyrrolidone. Furthermore, the present invention relates to a porous membrane obtainable by said method. Moreover, the present invention relates to the use of a specific solvent system for the production of a porous membrane.

A large-scale fabrication technique for PIM-1 asymmetric membranes doped with low-molecular-weight polyethylene glycol for gas separation. Based on the membrane fabrication technique of dry/wet phase inversion, firstly, the coagulation process of casting solution is regulated by low-molecular-weight polyethylene glycol to thin the dense functional layer, to improve the hydrophilicity of the membrane structure, and to form mass transfer channels for the diffusion of polyethylene glycol into the dense functional layer. Then, directional migration and enrichment of polyethylene glycol are realized through capillary action induced by directional water evaporation for large-scale fabrication of PIM-1 asymmetric membranes doped with low-molecular-weight polyethylene glycol in the dense functional layer for gas separation, and thereafter high permeation ability and high selectivity are achieved simultaneously.

Described are liquid-flowable, porous polyethylene filter membranes that include two opposing sides and that have an asymmetric pore structure; filter components and filters that include this type of porous polyethylene filter membrane; methods of making the porous polyethylene filter membranes, filter components, and filters; and methods of using a porous polyethylene filter membrane, filter component, or filter, to filter a fluid such as a liquid chemical to remove unwanted material from the fluid.

Asymmetric films, methods of making asymmetric films, and uses of asymmetric films. A method may include using at least two different solvents and at least one homopolymer and at least one block copolymer that can undergo self assembly, where the solvents are immiscible and have different surface tension, where, on film formation, all or substantially all of the block copolymer(s) migrate to an exterior surface of the homopolymer. The asymmetric films may include an isoporous region or layer and an asymmetric region or layer, where the asymmetric region does not include 10 percent by weight or more of the multiblock copolymer(s) and/or the isoporous region/layer and the asymmetric pore region/layer are not independently (or separately) formed and/or not laminated together to form the asymmetric film. The films can be used in devices, such as, for example, filtration devices.

Described are liquid-flowable, porous polyethylene filter membranes that include two opposing sides and that have an asymmetric pore structure; filter components and filters that include this type of porous polyethylene filter membrane; methods of making the porous polyethylene filter membranes, filter components, and filters; and methods of using a porous polyethylene filter membrane, filter component, or filter, to filter a fluid such as a liquid chemical to remove unwanted material from the fluid.

The present invention relates to a process for the production of asymmetric cellulose hollow fibres and the use of such fibres in the production of asymmetric carbon hollow fibre membranes (CHFMs). In particular, the present invention provides a facile and scalable process for the preparation of asymmetric CHFMs by direct pyrolysis of polymeric precursors without the need for complex pre-pyrolysis treatment steps to prevent pore collapse. The present invention also relates to the use of asymmetric CHFMs prepared according to said process in the separation of hydrogen gas from a mixed gas source, especially in the separation of hydrogen from CO.sub.2 in the steam-methane reforming reaction.

A fabrication technique for PIM-1 asymmetric membranes doped with polyethylene glycol for gas separation includes the following steps. Firstly, the coagulation process of casting solution is regulated by polyethylene glycol to thin the dense layer, to improve the hydrophilicity of the membrane structure, and to form mass transfer channels for the diffusion of polyethylene glycol into the dense layer. Then, directional migration and enrichment of polyethylene glycol are realized through capillary action induced by directional water evaporation for fabrication of PIM-1 asymmetric membranes doped with polyethylene glycol in the dense layer for gas separation.

Asymmetric hollow fiber membranes comprising a porous substrate layer and a skin layer are described. The skin layer is a copolymer of polymethyl pentene and polypropylene. Gas separation articles made using such hollow fiber membranes, as well as methods of making and using such hollow fiber membranes and gas separation articles are also described.