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.

Provided is a microporous polyolefin membrane which has excellent oxidation resistance and electrolyte injection performance and further has excellent permeability and strength balance. The multilayer, microporous polyolefin membrane has a first microporous layer containing polypropylene. The electrolyte injection performance is 20 seconds or less, at least one surface layer is the first microporous layer, and the PP distribution in the first microporous layer is uniform in the in-plane direction.

Hollow fiber membranes, membrane contactors, and related production and use methods. The membranes include a substrate having a multiplicity of pores and a skin layer overlaying the porous substrate. The porous substrate includes a first semi-crystalline thermoplastic polyolefin (co)polymer resin and a nucleating agent in an amount effective to achieve nucleation. The skin layer includes a second semi-crystalline thermoplastic polyolefin (co)polymer resin derived by polymerizing at most 98 wt. % of 4-methyl-1-pentene monomer with at least 2 wt. % of linear or branched alpha olefin monomers. Preferably, the first thermoplastic polyolefin (co)polymer is different from the second thermoplastic polyolefin (co)polymer. The skin layer is less porous than the porous substrate and forms an outer surface of the hollow fiber with the porous substrate forming an inner surface. The hollow fibers are formed by co-extruding the porous substrate resin and the skin layer resin through an annular die.

A dry-process porous membrane having an oxygen induction time (OIT) greater than 3 minutes, greater than 5 minutes, greater than 10 minutes, greater than 15 minutes, greater than 20 minutes, or greater than 25 minutes where OIT is measured at 215? C. and 100% O.sub.2. The dry-process porous membrane may be a microporous polyolefin membrane.

A method suppresses membrane thickness variation and air resistance variation after a compression at 60 C. or 80 C. Stretching is performed at least twice in at least different axial directions before the extraction of the solvent, and at the same time, at least one of (i) and (ii) is satisfied. (i) The step (c) is a first stretching step of stretching the sheet-shaped product at least once in a sheet transport direction (MD direction) and at least once in a sheet width direction (TD direction) individually, and the MD stretching magnification and the TD stretching magnification in the step (c) satisfy (TD stretching magnification MD stretching magnification2). (ii) The stretching temperature (T1) of a first axial stretching performed firstly in the step (c) and the maximal stretching temperature (T2) of a second stretching performed after the first axial stretching satisfy (T1T20).

The invention relates to the field of membrane gas separation. A method of removing components of gas mixtures which is based on passing the components of a gas mixture through a nanoporous membrane and subsequently selectively absorbing them with a liquid absorbent that is in contact with the nanoporous membrane, wherein to prevent the gas from getting into the liquid phase of the absorbent and the liquid phase of the absorbent from getting into the gas phase, a nanoporous membrane with homogeneous porosity (size distribution less than 50%) and a pore diameter in the range of 5-500 nm is used, and the pressure differential between the gas phase and the liquid absorbent is kept below the membrane bubble point pressure. An acid gas removal performance of more than 0.3 nm.sup.3/(m.sup.2 hour) in terms of CO.sub.2 is achieved at a hollow-fiber membrane packing density of up to 3200 m.sup.2/m.sup.3, which corresponds to a specific volumetric performance of acid gas removal of up to 1000 nm.sup.3 (m.sup.3 hour). The technical result is that of providing effective extraction of undesirable components from natural and process gas mixtures.

Features of relatively low pressure microporous (and preferably plant-responsive) irrigation tubes are combined with features of relatively high pressure drip emitter tubes to produce a hybrid irrigation tube. Methods for using and manufacturing the hybrid irrigation tube are also disclosed.

Embodiments relate generally to a filter (110), for example, for attachment onto a gas detector device or a gas sensor, and attempt to improve the efficiency and service life of the filter (110). Embodiments typically comprise a dustproof membrane (114) and a waterproof membrane (113). Some embodiments may also comprise a splash-proof cap (130) and/or features to reduce negative pressure on the filter (110).

Provided is a novel continuous single-step method of manufacturing a multilayer sorbent polymeric membrane having superior productivity, properties and performance. At least one layer of the polymeric membrane comprises sorbent materials and a plurality of interconnecting pores. The method includes: (a) coextruding layer-forming compositions to form a multilayer coextrudate; (b) casting the coextrudate into a film; (c) extracting the film with an extractant; and (d) removing the extractant from the extracted film to form the multilayer sorbent polymeric membrane. The sorbent membrane of this disclosure can find a wide range of applications for use in filtration, separation and purification of gases and fluids, CO.sub.2 and volatile capture, structural support, vehicle emission control, energy harvesting and storage, electrolyte batteries, device, protection, permeation, packaging, printing, and etc.

Provided herein are tubular membrane filter elements, tangential flow filtration systems comprising such filter elements and methods of using such filter elements and filtration systems.