Organic solvent nanofiltration membranes that include at least one polymer coated expanded polyparaxylylene (eP-PX) membrane are provided. A substrate/support layer may be positioned on one side of the ePPX membrane. In some embodiments, the substrate/support layer is sandwiched between ePPX membranes. Processes for manufacturing and using such organic solvent nanofiltration membranes are also provided. The organic solvent nanofiltration membranes are capable of separating and/or concentrating solutes from a solution comprising a lower molecular weight organic solvent with high permeability. The polymer coated ePPX membranes may also be resistant to chemical attack, resistant to gamma radiation, thermally stable, biocompatible, and strong.

A provided stretched porous polytetrafluoroethylene membrane has an air permeability of 4 cm.sup.3/(sec.Math.cm.sup.2) or more, as expressed in terms of Frazier air permeability, in a thickness direction, and has a total cohesion of 1.9 (N/20 mm).sup.2 or more, the total cohesion being expressed by a product of a peel cohesion in a first in-plane direction and a peel cohesion in a second in-plane direction perpendicular to the first direction. The above stretched porous membrane is highly air-permeable and, for example, when included in a filter member, being less likely to suffer breakage at the time of handling the member or placing the member on a housing or the like.

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.

Compositions and methods directed to the production of single layer, highly porous, free-standing polytetrafluoroethylene (PTFE) membranes having macro-textured surfaces are provided. The macro-textured surfaces are due to the presence of macroscopic nodal aggregates within the membrane that are connected by fibrils The membranes have high porosity, high airflow, and a bulk density less than 1.0 g/cm3. Articles comprising the porous, single layer PTFE membranes are also provided.

A provided stretched porous polytetrafluoroethylene membrane has a node-fibril structure including a plurality of nodes and a fibril connecting the plurality of nodes. A ratio of an average length of the plurality of nodes in a thickness direction of the stretched porous polytetrafluoroethylene membrane to a thickness of the stretched porous polytetrafluoroethylene membrane is 10% or more. The above stretched porous polytetrafluoroethylene membrane is less likely to suffer breakage. In the above stretched porous polytetrafluoroethylene membrane, assuming that there is a cuboid region having an upper surface and a lower surface respectively positioned at one membrane surface and the other membrane surface of the stretched porous polytetrafluoroethylene membrane, the number of the nodes included in the region may be 4 or less per micrometer thickness, the upper surface and the lower surface each having dimensions of 280 μm×280 μm.

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 μm or more, the filter portion has a thickness of 140 μm or less, and the filter portion has a density of 0.60 g/cm.sup.3 or less.

Polytetrafluoroethylene (PTFE) composite articles that have a macro textured surface. The composite articles include at least two different PTFE membranes in a layered or stacked configuration. The composite article has a macro textured surface characterized by a plurality of strands raised from the surface of the PTFE membrane. The strands may be formed of either interconnected nodes of PTFE or of at least one nodal mass of PTFE and have a length equal to or greater than about 1.5 mm. The macro textured surface provides a topography to the first PTFE membrane. The composite articles have a bubble point from about 3.0 psi to about 200 psi, a thickness from about 0.01 to about 3.0 mm, and a bulk density from about 0.01 g/cm.sup.3 to about 1.0 g/cm.sup.3.

Provided is a porous membrane including polytetrafluoroethylene and/or modified polytetrafluoroethylene having a small pore diameter, thin film thickness, high porosity, and high strength; and a method for manufacturing the same. The porous membrane including polytetrafluoroethylene and/or modified polytetrafluoroethylenehas bubble point of isopropyl alcohol according to JIS K3832 of 600 kPa or more, and tensile strength according to JIS K6251 of 90 MPa or more.

Hollow fiber membranes, membrane contactors, and related production and use methods. The asymmetric hollow fiber membranes include a porous substrate having a multiplicity of pores and including at least one semi-crystalline thermoplastic polyolefin (co)polymer. A skin layer including at least one polydiorganosiloxane polyoxamide copolymer overlays the porous substrate. The skin layer is less porous than the porous substrate and forms an outer surface of the asymmetric hollow fiber membrane, while the porous substrate forms an inner surface of the hollow fiber membrane. The skin layer is preferably nonporous.

The problem of the present invention is to provide a novel polytetrafluoroethylene porous film having a small pore diameter, small film thickness, high porosity, and high strength, and a production method thereof.

The present invention provides a polytetrafluoroethylene porous film, wherein a bubble point in isopropyl alcohol (IPA) according to JIS K3832 is not less than 400 kPa, and a tensile strength based on JIS K6251 is not less than 50 MPa.