A method for producing a microporous material comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a filler; providing a processing plasticizer; adding the filler to the UHMWPE in a mixture being in the range of from about 1:9 to about 15:1 filler to UHMWPE by weight; adding the processing plasticizer to the mixture; extruding the mixture to form a sheet from the mixture; calendering the sheet; extracting the processing plasticizer from the sheet to produce a matrix comprising UHMWPE and the filler distributed throughout the matrix; stretching the microporous material in at least one direction to a stretch ratio of at least about 1.5 to produce a stretched microporous matrix; and subsequently calendering the stretched microporous matrix to produce a microporous material which exhibits improved physical and dimensional stability properties over the stretched microporous matrix.

A method for treating a surface of a microporous membrane includes: (1) contacting at least one surface of the membrane with a treatment composition including: (a) an acrylic polymer prepared from a mixture of vinyl monomers including: (i) a (meth)acrylic acid monomer and (ii) a silane-functional acrylic monomer; and (b) a base, where the acrylic polymer is in contact with the filler present in the matrix; and (2) subjecting the membrane of (1) to conditions sufficient to effect a condensation reaction between the filler and the acrylic polymer. A treated microporous membrane and an aqueous treatment composition are also disclosed.

A composite porous membrane contains at least one porous base layer and at least one uniaxially stretched coating layer located on at least one side surface of the porous base layer. For example, the composite porous membrane comprises at least one porous base layer and at least one nanofiber-like non-polyolefin polymer porous layer oriented along the transverse stretching direction of the composite porous membrane and located on one or two side surfaces of the porous base layer, or the composite porous membrane comprises a biaxially stretched polypropylene porous base layer and a uniaxially stretched coating layer located on at least one side surface of the porous base layer. The composite porous membrane is coated with a coating solution prior to transversely stretching. The nanofiber-like non-polyolefin polymer porous layer may reduce cracking of the composite porous membrane in the machine direction.

A hollow fiber membrane of the present invention is a hollow fiber membrane having an outer surface and an inner surface, wherein the inner surface has a zebra stripe pattern in which dense portions and porous portions are alternately formed in the longitudinal direction, and the outer surface has a maximum pore size of about 1 m or less (about 1 m), and wherein the hollow fiber membrane has a water permeability (flux) of about 1,300 LMH/bar to about 5,000 LMH/bar.

Disclosed are a method of manufacturing a polyethylene membrane comprising: stretching a polyethylene film in a first direction during a first stretching; attaching a plurality of rods on side edges of the polyethylene film; attaching a tape on the polyethylene film; stretching the polyethylene film having the rods attached thereto in a second direction during a second stretching; and annealing the polyethylene film after the second stretching. The second direction can be a transverse direction of the first direction, and the first stretching and the second stretching can be performed at the same (or higher) temperature and the same stretching speed as each other.

Provided is an internal pressure adjustment member to be attached to an outer surface of a housing, the member having high air permeability even when a differential pressure that can be generated between the inside and the outside of a housing to which the internal pressure adjustment member is attached is small, and inhibiting damage to the member and a reduction in the air permeability of the member due to coming soil and mud. The internal pressure adjustment member includes: a filter portion including a net-like or mesh-like support layer and first and second porous polytetrafluoroethylene (PTFE) membranes laminated on the support layer such that the support layer is interposed therebetween, the first porous PTFE membrane being exposed on one surface of the filter portion, the second porous PTFE membrane being exposed on another surface of the filter portion; and an adhesive portion, formed on the one surface of the filter portion, for attaching the filter portion to the outer surface of the housing. The first porous PTFE membrane and the second porous PTFE membrane each have an average pore diameter of 2.0 m or more, the filter portion has a thickness of 140 m or less, and the filter portion has a density of 0.60 g/cm.sup.3 or less.

The present invention provides a method for preparing a porous membrane of a fluorine-based resin having an improved shrinkage while maintaining excellent filtration efficiency and air permeability.

A novel or improved base film for impregnation, impregnated base film, product incorporating the impregnated base film, and/or related methods as shown, claimed or described herein.

A polyolefin packaging film is provided. The polyolefin film is formed by a thermoplastic composition containing a continuous phase that includes a polyolefin matrix polymer and nanoinclusion additive is provided. The nanoinclusion additive is dispersed within the continuous phase as discrete nano-scale phase domains. When drawn, the nano-scale phase domains are able to interact with the matrix in a unique manner to create a network of nanopores.

A catalytic composite is formed of a catalytic layered assembly including a porous catalytic fluoropolymer film and one or more felt batts connected with the porous catalytic fluoropolymer film. At least one felt batt is positioned adjacent the upstream side of the porous catalytic fluoropolymer film to form the catalytic composite. The fluoropolymer film is perforated to allow for enhanced airflow therethrough while retaining the capability of catalyzing the reduction or removal of chemical species in fluid flowing through the catalytic composite.