A polymer or polymer composite membrane having through-thickness micropores and a method of preparing the same are provided. More particularly, a polymer or polymer composite membrane having a pore structure such that micropores are aligned in a mesh structure in the thickness direction of the polymer or polymer composite membrane due to unidirectional freezing in the thickness direction of a solvent. The membrane has through-thickness micropores, and thus has improved permeability in the thickness direction and superior uniformity in size of the micropores and wall thickness between the micropores. For these reasons, the membrane can be used for a porous membrane substrate, microfiltration membrane, etc.

One or more polymeric hollow fiber membranes are pyrolyzed to form one or more hollow fiber CMS membranes by directing a flow of pyrolysis gas through a polymeric membrane cartridge (including a porous center tube around which one or more green, polymeric, hollow fiber membranes is arranged) or a bundle of polymeric membranes (including a plurality of green, polymeric hollow fiber membranes oriented so that their ends are disposed with ends of the bundle) in a direction perpendicular to a length direction of the cartridge or bundle in order to sweep away off-gases that are formed during pyrolysis.

One or more polymeric hollow fiber membranes are pyrolyzed to form one or more hollow fiber CMS membranes by directing a flow of pyrolysis gas through a polymeric membrane cartridge (including a porous center tube around which one or more green, polymeric, hollow fiber membranes is arranged) or a bundle of polymeric membranes (including a plurality of green, polymeric hollow fiber membranes oriented so that their ends are disposed with ends of the bundle) in a direction perpendicular to a length direction of the cartridge or bundle in order to sweep away off-gases that are formed during pyrolysis.

One or more polymeric hollow fiber membranes are pyrolyzed to form one or more hollow fiber CMS membranes by directing a flow of pyrolysis gas through a bundle of polymeric membranes (including a plurality of green, polymeric hollow fiber membranes oriented so that their ends are disposed with ends of the bundle) in a direction perpendicular to a length direction of the bundle in order to sweep away off-gases that are formed during pyrolysis.

A method for preparing the network-pore polyvinylidene fluoride membrane based on polyvinyl alcohol (PVA) gel includes the steps of (1) mix and stir PVA, masking agent and solvent, heat and dissolve the mixture evenly under 105 degree Celsius to obtain a PVA solution; (2) in the PVA solution, add PVDF and pore-forming agent, where the rest shall be added with the solvent until the total mass fraction sum is 1, stir, heat and dissolve the solution evenly to obtain the homogeneous casting solution; (3) the casting solution is filtered, deaerated, phase-separated and solidified as membrane A; (4) removes the PVA gel from membrane A to obtain membrane B; (5) membrane B is washed with water to remove the residual solvent to obtain the PVDF membrane with network-pore structure. The resulting PVDF membrane is an asymmetric membrane with an ultra-thin cortex and an interpenetrating network-pore sub-cortex structure.

Membranes having a permselective active layer of a copolymerized perfluorinated monomer and an non-fluorinated alkylvinylester monomer demonstrate superior selective permeability performance for separating gas mixtures compared to membranes of exclusively perfluorinated polymers. Preferred active layer compositions are copolymers of perfluoro-2,2-dimethyl-1,3 dioxole (PDD) copolymerized with an alkylvinyl ester such as vinyl acetate, and vinyl pivalate, and with alkylvinyl esters that are substantially hydrolyzed to provide copolymerized vinyl alcohol functionality. The membranes can have a thin, high diffusion rate, gutter layer of a fluorinated polymer highly permeable to nitrogen positioned between the active layer and a porous support layer. A novel copolymer effective in selectively permeable membranes is a copolymer of PDD and an alkylvinyl ester compound having the formula H.sub.2C?CHOC(0)R.sup.1 in which R.sup.1 is a linear or branched alkyl group of from 2 to 5 carbon atoms.

The invention concerns polyimide membranes, preferably composed of P84 type 70 or P84 HT, having improved chemical and physical properties, a method of producing same and also their use.

A thermally-crosslinked membrane comprising a poly(1,2,4-triazole)-polymer that includes recurring hydroxyl-functionalized triazole units is described. The polymer has the structure of formula I: (I) wherein Ar describes an aromatic or heteroaromatic group, particularly with substituents and/or a multi-ring system, X describes a N group of the formula OR.sup.2, wherein R.sup.2 is a hydrogen atom or a group with 1 to up to 20 carbon atoms; Y describes a bond or a group with 1 to up to 20 carbon atoms, Z describes a group of the common formula SO.sub.3R.sup.1 or PO(OR.sup.1).sub.2, wherein R.sup.1 is a hydrogen atom or an alkali metal, and q is a whole number between 0 and 4, wherein n is a natural number 10, wherein at least one crosslink is present between two of the hydroxyl-functionalized Ar moieties of the polymer. Methods of making the thermally-crosslinked membranes and separation methods using the thermally-crosslinked membranes are provided.

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The invention concerns polyimide membranes, preferably composed of P84 type 70 or P84 HT, having improved chemical and physical properties, a method of producing same and also their use.

A microporous membrane is made by a dry-stretch process and has substantially round shaped pores and a ratio of machine direction tensile strength to transverse direction tensile strength in the range of 0.5 to 5.0. The method of making the foregoing microporous membrane includes the steps of: extruding a polymer into a nonporous precursor, and biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction stretching including a simultaneous controlled machine direction relax.