A sheet comprising a plexifilamentary film-fibril network consisting essentially of high density polyethylene in an overlapping multi-directional configuration, the sheet, as-produced from a spin cell, having a normalized Frazier air permeability of between 0.002 and 0.2 m.sup.3/m.sup.2.Math.minute at 50 gsm, a BET surface area of between 9 and 20 m.sup.2/gm, and a normalized hydrohead of between 150 and 250 cm at 50 gsm, wherein the plexifilamentary film-fibril network in an overlapping multi-directional configuration is flash-spun from a spin fluid comprising polymer and spin agent, the spin fluid temperature being 190° C. or greater, the spin agent comprising dichloromethane, the spin fluid having a polymer concentration of 12 to 14 weight percent.

A sheet having a plexifilamentary structure with a normalized Frazier air permeability of between 0.002 and 0.2 (m.sup.3/m.sup.2.Math.minute)@50 gsm, and a normalized hydrohead of between 150 and 250 centimeters@50 gsm.

A sheet having a plexifilamentary structure with a normalized Frazier air permeability of between 0.002 and 0.2 (m.sup.3/m.sup.2.Math.minute)@50 gsm, and a normalized hydrohead of between 150 and 250 centimeters@50 gsm.

Disclosed is a method for the manufacture of fibrous yarn including the steps, where an aqueous suspension including fibers and at least one rheology modifier is provided, followed by directing the suspension through at least one nozzle, to form at least one yarn, and then dewatering the yarn.

Disclosed is a method for the manufacture of fibrous yarn including the steps, where an aqueous suspension including fibers and at least one rheology modifier is provided, followed by directing the suspension through at least one nozzle, to form at least one yarn, and then dewatering the yarn.

A sheet comprising a plexifilamentary film-fibril network consisting essentially of high density polyethylene in an overlapping multi-directional configuration, the sheet, as-produced from a spin cell, having a normalized Frazier air permeability of between 0.002 and 0.2 m.sup.3/m.sup.2.Math.minute at 50 gsm, a BET surface area of between 9 and 20 m.sup.2/gm, and a normalized hydrohead of between 150 and 250 cm at 50 gsm, wherein the plexifilamentary film-fibril network in an overlapping multi-directional configuration is flash-spun from a spin fluid comprising polymer and spin agent, the spin fluid temperature being 190 C. or greater, the spin agent comprising dichloromethane, the spin fluid having a polymer concentration of 12 to 14 weight percent.

A sheet comprising a plexifilamentary film-fibril network consisting essentially of high density polyethylene in an overlapping multi-directional configuration, the sheet, as-produced from a spin cell, having a normalized Frazier air permeability of between 0.002 and 0.2 m.sup.3/m.sup.2.Math.minute at 50 gsm, a BET surface area of between 9 and 20 m.sup.2/gm, and a normalized hydrohead of between 150 and 250 cm at 50 gsm, wherein the plexifilamentary film-fibril network in an overlapping multi-directional configuration is flash-spun from a spin fluid comprising polymer and spin agent, the spin fluid temperature being 190 C. or greater, the spin agent comprising dichloromethane, the spin fluid having a polymer concentration of 12 to 14 weight percent.

A separator medium for electrochemical cells that contains at least one nonwoven sheet of polymeric fibers. The nonwoven sheet has a surface area of about 0.5 to about 1.5 m.sup.2/g and has a maximum pore size that is equal to or more than 2.5 times the mean flow pore size and more than 11 times the minimum pore size. The sheet may be sulfonated to a level of 0.67% and demonstrates superior tensile properties after sulfonation and relative to previously known separators.

A separator medium for electrochemical cells that contains at least one nonwoven sheet of polymeric fibers. The nonwoven sheet has a surface area of about 0.5 to about 1.5 m.sup.2/g and has a maximum pore size that is equal to or more than 2.5 times the mean flow pore size and more than 11 times the minimum pore size. The sheet may be sulfonated to a level of 0.67% and demonstrates superior tensile properties after sulfonation and relative to previously known separators.

Fibers, yarns, woven fabric including the yarns and fibers, and methods of manufacturing the same are disclosed. Fibers can include base material staple fibers and dissolvable or water-soluble fibers that are mixed together to define an ultra-homogenous yarn comprising base material and dissolvable material, which is provided in at least the warp direction to form a woven fabric having a 7-end, 8-end or 10-end sateen weave. A processing step provides for the removal of the dissolvable fibers to produce a yarn defining a plurality of pores that are uniformly distributed throughout the structure of the yarn. The woven fabric has a thread count between 450-1200. The woven fabric is thermally-insulative, breathable and moisture-wicking.