Microporous polymer membranes and related methods of fabrication are provided. An asymmetric microporous membrane embodiment includes, but is not limited to, a thermoplastic polymer substrate defining a plurality of micropores, the thermoplastic polymer including one or more of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and a combination thereof; and a polymethylpentene (PMP) polymer skin positioned on the thermoplastic polymer substrate, wherein when the thermoplastic polymer substrate includes PMP, the PMP polymer skin has a crystallinity that differs from a crystallinity of the PMP in the polymer substrate.

A tetrafluoroethylene polymer is provided in an air filter medium having a pressure loss that can be reduced and made uniform at a plurality of positions. The tetrafluoroethylene polymer may also be provided in an air filter medium, a filter pack, or an air filter unit. The tetrafluoroethylene polymer has drawability and non-melt processability. The tetrafluoroethylene polymer has a ratio S.sub.2/S.sub.1 of 0.60 or more, where S.sub.2 represents an endotherm mJ/mg in a range of T.sub.0 C. or higher and 350 C. or lower, T.sub.0 C. is a temperature 2.5 C. lower than a temperature T.sub.p C. (340T.sub.p345) at which a minimum point is given on a heat-of-fusion curve obtained by measuring an unbaked polymer for measurement having no history of heating to a temperature of 300 C. or higher using a differential scanning calorimeter at a temperature-increasing rate of 2 C./min, and S.sub.1 represents an endotherm mJ/mg in a range of 320 C. or higher and T.sub.0 C. or lower.

Provided are a polyethylene microporous membrane, a method for manufacturing the same, and a separator including the microporous membrane. According to an embodiment of the present disclosure, a microporous membrane is provided which includes a polyethylene having a weight average molecular weight of 1?10.sup.5 g/mol to 10?10.sup.5 g/mol, and has a thickness of 3 ?m to 20 ?m, a puncture strength of 0.25 N/?m or more, a gas permeability of 1.5?10.sup.?5 Darcy or more, a shrinkage rate in the transverse direction of 10% or less as measured after being allowed to stand at 131? C. for 1 hour, a tensile strength in the machine direction of 1500 kg/cm.sup.2 or more, a tensile strength in the transverse direction of 2000 kg/cm.sup.2 or more, and a ratio between the tensile strength in the machine direction and the tensile strength in the transverse direction of 0.5 to 0.7.

Provided are a polyethylene microporous membrane, a method for manufacturing the same, and a separator including the microporous membrane. According to an embodiment, a polyethylene microporous membrane which has a thickness of 3 ?m to 30 ?m, a puncture strength of 0.15 N/?m or more, a shrinkage rate in the transverse direction of 5% or less as measured after being allowed to stand at 121? C. for 1 hour, and a PS index represented by the following Equation 1 of 110 or more is provided:

PS index=[gas permeability (?10.sup.31 5 Darcy)?porosity (%)]+[shrinkage rate (%) in the transverse direction at 121? C.]. [Equation 1]

Provided are a polypropylene microporous membrane, a method for manufacturing the same, and a separator including the microporous membrane. According to an embodiment, a polypropylene microporous membrane including a polypropylene having a viscosity average molecular weight of 1?10.sup.6 g/mol to 3?10.sup.6 g/mol, a thickness of 3 ?m to 30 ?m, and exhibits a puncture strength of 0.20 N/?m or more, a gas permeability of 1.0?10.sup.?5 Darcy or more, and a shrinkage rate in the transverse direction of 20% or less as measured after being allowed to stand at 150? C. for 1 hour, is provided.

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.

Disclosed is a membrane with one or more dry-process porous layers that comprise (1) a polyolefin and (2) a product formed by reacting two components, which may be a compound with one or more carboxy groups and a compound with one or more epoxy groups. The product may be a reaction network, a three-dimensional reaction network, or a cross-linked network The resulting membrane has improved strength, reduced splittiness, or both improved strength and reduced splittiness. The membrane may be used in a battery, capacitor, HVAC, filtering device, or textile. Methods for making the membrane are also disclosed.

A hollow fiber membrane and a method of preparing the same. The hollow fiber membrane has an inner surface and an outer surface, wherein the inner surface has a zebra-stripe pattern in which a dense portion and a porous portion are alternately formed in a longitudinal direction of the hollow fiber membrane.

The invention relates to a method for producing a dispersion of nanoscale dicarboxylic acid salts, to the use of these dispersions for producing a compound, and to the use for producing films. The invention further relates to the use of the compounds for producing films.

A film-stretching apparatus in accordance with an aspect of the present invention includes a stretching furnace which has (i) an entrance through which a material film is transferred into the stretching furnace and (ii) an exit through which the material film having been stretched is transferred out of the stretching furnace, an airflow in the entrance being controlled so as to be directed toward an outside of the stretching furnace.