The present invention is generally related to a high capacity, high efficiency nonwoven filtration media comprising a gradient pore structure. In particular, the filtration media can comprise thermoplastic synthetic microfibers, fibrillated fibers, staple fibers, and a binder. Furthermore, the filtration media may be produced without the use of glass fibers or microglass fibers. A process for making the filtration media is also provided. Consequently, the filtration media of the present invention does not cause the same issues as conventional filtration media that comprises glass fibers and/or microglass fibers. Moreover, the filtration media can be used to treat fuel, lubrication fluids, hydraulic fluids, and various other industrial gases.

The invention provides a modified cross-section fiber is provided having a single fiber fineness of 0.01 to 1.0 dtex and modified cross-section degree (, =P/(4A).sup.1/2, where P represents a peripheral length (m) in a fiber cross section, and A represents an area of the fiber cross section (m.sup.2)) of 1.5 to 4.0 at a fiber cross section taken along a direction perpendicular to the fiber axis.

Disclosed herein are nanofiber structures, and methods of making and using the same. In some embodiments, provided is a porous sheet comprising a plurality of nanofibers in contact with a supporting structure comprising a plurality of supporting elements, wherein: the nanofibers have an average diameter of about 10-900 nm; the supporting elements have an average thickness less than, about equal to, or greater than that of the thickness of the nanofibers; the sheet has an average thickness that is about 75%-150% of an average thickness of the supporting elements; a total volume of the nanofibers is less than about 20% of a total volume of the porous sheet; and/or a total volume of the supporting structure is less than about 50% of the total volume of the porous sheet. In some embodiments, provided is a multilayer structure comprising one or more sections, where each section independently comprises one or more porous sheets as described herein.

A nonwoven filtration medium that includes a fibrous base media including synthetic and/or natural fibers and microfibrillated cellulose fibers.

A method for arranging nanotube elements within nanotube fabric layers and films is disclosed. A directional force is applied over a nanotube fabric layer to render the fabric layer into an ordered network of nanotube elements. That is, a network of nanotube elements drawn together along their sidewalls and substantially oriented in a uniform direction. In some embodiments this directional force is applied by rolling a cylindrical element over the fabric layer. In other embodiments this directional force is applied by passing a rubbing material over the surface of a nanotube fabric layer. In other embodiments this directional force is applied by running a polishing material over the nanotube fabric layer for a predetermined time. Exemplary rolling, rubbing, and polishing apparatuses are also disclosed.

The invention relates to a method for manufacturing a nonwoven fabric having an air permeability of 2000 l/m.sup.2/s or less when measured at a pressure difference of 200 Pa according to EN ISO 9237, the method comprising the steps of: providing at least two sets of fibers, wherein a first fiber set comprises a significant level of splittable fibers and a second fiber set comprises a low level of splittable fibers or no splittable fibers; using the first fiber set to form at least one first fibrous web in a first web formation process and using the second fiber set to form at least one second fibrous web in a second web formation process; stacking the first and second webs so obtained to provide a multilayer web including two distinct layers of fibrous webs; and bonding the multilayer web. The invention further relates to a nonwoven fabric obtainable by such process and the use of such nonwoven fabric in acoustic isolation applications.

Nanofiber filter media ribbons are flexible elongate strips of polymeric material having a surface on which is formed an array of nanofibers. Ribbons are formable into woven or non-woven mats. The array of nanofibers can be configured to filter a predetermined contaminant from a fluid stream passing through the mats. Filter ribbons are formable by applying a moldable polymer to a first angular location of a rotating cylindrical roll having an array of nanoholes formed in a circumferential surface thereof so that the polymer covers the surface of the roll and infiltrates the nanoholes; cooling the polymer while rotating the polymer-covered roll to a second angular position; and removing the cooled polymer from the roll as an elongate film having an array of nanofibers formed on a surface thereof by the polymer that infiltrated the nanoholes.

Nanofiber filter media ribbons are flexible elongate strips of polymeric material having a surface on which is formed an array of nanofibers. Ribbons are formable into woven or non-woven mats. The array of nanofibers can be configured to filter a predetermined contaminant from a fluid stream passing through the mats. Filter ribbons are formable by applying a moldable polymer to a first angular location of a rotating cylindrical roll having an array of nanoholes formed in a circumferential surface thereof so that the polymer covers the surface of the roll and infiltrates the nanoholes; cooling the polymer while rotating the polymer-covered roll to a second angular position; and removing the cooled polymer from the roll as an elongate film having an array of nanofibers formed on a surface thereof by the polymer that infiltrated the nanoholes.

Methods for characterizing a nanotube formulation with respect to one or more particular ionic species are disclosed. Within the methods of the present disclosure, this characterization provides control over the surface roughness (or smoothness) and the degree of rafting within a nanotube fabric formed form such a nanotube formulation. In one aspect, the present disclosure provides a nanotube formulation roughness curve (and methods for generating such a curve) that can be used to select a utilizable range of ionic species concentration levels that will provide a nanotube fabric with a desired surface roughness (or smoothness) and degree of rafting. In some aspects of the present disclosure, such a nanotube formulation roughness curve can be used adjust nanotube formulation prior to a nanotube formulation deposition process to provide nanotube fabrics that are relatively smooth with a low degree of rafting.

A nonwoven web comprising a layer of polymeric fibers, wherein, based on the total number of polymeric fibers, at least 10% the polymeric fibers in said layer are coarse fibers having a fiber diameter of 4 m or more, and at least 10% of the polymeric fibers in said layer are fine fibers having a fiber diameter of 2 m or less. Also described herein is a method for making the nonwoven web, comprising melt-blowing a polymer mixture comprising two immiscible or partially miscible polymers.