A porous membrane according to the present disclosure includes polytetrafluoroethylene as a main component, wherein a melting curve obtained in a first run of differential scanning calorimetry at a rate of temperature increase of 10 C./min has an endothermic peak in a range of 300 C. to 360 C., and a difference between an onset temperature and an endset temperature of the endothermic peak is 20 C. or less.

The present disclosure relates to a micro or nano porous membrane composed of a stretched membrane of a fluororesin membrane, wherein the fluororesin membrane contains sintered bodies of a plurality of core-shell particles containing fluororesins, wherein the core-shell particles include cores and shells covering outer surfaces of the cores, wherein an average particle size of the core-shell particles before being sintered is greater than or equal to 100 nm and less than or equal to 1,000 nm, wherein a ratio of a volume of the shells to a volume of the cores in the core-shell particles before being sintered is greater than or equal to 2/98 and less than or equal to 50/50, wherein a fluororesin of the cores is a tetrafluoroethylene-hexafluoropropylene copolymer, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer or a combination thereof, and a fluororesin of the shells is polytetrafluoroethylene, and wherein a first heat of fusion of the fluororesins in the core-shell particles is less than or equal to 68 J/g.

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.

A porous membrane comprising PTFE blended with PFSA is disclosed.

Disclosed are hydrophilic porous PTFE membranes comprising PTFE and an amphiphilic copolymer, for example, a copolymer of the formula:

##STR00001##

wherein m and n are as described herein. Also disclosed are a method of preparing hydrophilic porous PTFE membranes and a method of filtering fluids through such membranes.

Disclosed are hydrophilic porous PTFE membranes comprising PTFE and an amphiphilic copolymer of the formula (I):

##STR00001##

wherein Rf, Rh.sub.1, Rh.sub.2, Y, m, n, and o are as described herein. Also disclosed are a method of preparing hydrophilic porous PTFE membranes and a method of filtering fluids through such membranes.

Polyparaxylylene (PPX) polymers that can be expanded into porous articles that have a node and fibril microstructure are provided. The fibrils contain PPX polymer chains oriented with the fibril axis. The PPX polymer may contain one or more comonomer. PPX polymer articles may be formed by applying PPX to a substrate by vapor deposition. The nominal thickness of the PPX polymer film is less than about 50 microns. The PPX polymer film may be removed from the substrate to form a free-standing PPX polymer film, which may then be stretched into a porous article. Alternatively, a PPX polymer article can be formed by lubricating PPX polymer powder, heating the lubricated powder, and calendering or ram extruding to produce a preform that can subsequently be stretched into a porous article. The heating and expansion temperatures are from about 80 C. to about 220 C. or from about 220 C. to about 290 C. or from about 290 C. to about 450 C.

The present invention is directed to methods of separating a fluid emulsion stream into a hydrocarbon stream and an aqueous stream, by contacting the stream with a microporous membrane to yield a hydrocarbon product stream and an aqueous product stream. The membrane comprises a substantially hydrophobic, polymeric matrix, and substantially hydrophilic, finely divided, particulate, substantially water-insoluble filler distributed throughout the matrix. The polymeric matrix has a mean pore size less than 1.0 micron, and the purities of the product streams are independent of the flux rate of the aqueous product stream and the pore size of the membrane.

The present invention aims to provide a biaxially stretched porous membrane having high strength, a small pore size, and excellent homogeneity. The biaxially stretched porous membrane of the present invention includes polytetrafluoroethylene obtained by copolymerizing tetrafluoroethylene and perfluoro(methyl vinyl ether).

A method for making a filter membrane includes: forming a polymer layer; applying a plurality of nanoparticles on the polymer layer, the nanoparticles being self-assembled to form a closed pack arrangement on the polymer layer; heating the nanoparticles such that a portion of the polymer layer contacting the nanoparticles is softened so that the nanoparticles are sunk into the polymer layer; and removing the nanoparticles from the polymer layer so that the polymer layer is formed with a plurality of pores penetrating the polymer layer and being arranged in a honeycomb pattern.