Common Terms in the Nonwoven & Filtration Industries
Abrasion resistance:
The ability of a surface to resist wear by friction.
Agglomeration:
The act of amassing a clump or cluster of particles.
Absorption:
The process of a gas or liquid being assimilated or incorporated into a nonwoven filter fabric
Antistat:
A chemical agent that reduces, or assists the dissipation of, the electrical charges that typically arise during the processing of fibers or fabrics.
Terms used for Fibers and Fabric in Dry Filtration
Air-to-Cloth Ratio:
Velocity of airflow in a one-minute, i.e. 5-1 means metres of air in one minute.
A general term for any system of woven fibers which interlaces on the back of a textile material; a fabric which is bonded to a vinyl or other plastic sheet material.
Bonding:
The process of combining fibers into sheets, webs or battings by means of adhesives, plastics, entanglement or heat.
Bicomponent:
Fibers composed of two or more polymer types in a sheath-core or side-by-side (bilateral) relation.
Breaking Length:
The calculated length of a specimen whose weight is equal to its breaking load; the breaking strength of a fabric strip divided by its basis weight.
Binder fibers:
Fibers having a relatively low softening point compared to other fibers in the web, and which, upon the application of heat and pressure, act as an adhesive.
Bursting Strength:
A measure of the ability of a nonwoven fabric to resist rupture by pressure.
Calender:
A machine used in the finishing process that imparts a variety of surface effects to fabrics. It essentially consists of two or more heavy rollers, sometimes heated, between which the fabric passes under pressure.
Continuous Filament:
A fiber of an indefinite or extreme length, such as found naturally in silk. Man-made fibers are extruded as continuous filaments which may be converted into staple fiber by chopping.
Calendering:
A mechanical finishing process for fabrics to produce special effects, such as higher luster, glazing moiré and embossed effects.
In the production of nonwovens, an individual or an organization that transforms nonwoven fabrics in roll-form into finished products. In woven and knit textiles, an individual or organization that buys greige fabrics; arranges for them to be dyed, printed and/or finished; and sells them to apparel manufacturers, wholesalers, retailers and others.
Carding:
A process in the manufacture of fibrous webs in which the staple is opened, cleaned, alighted and formed.
Crimp:
The waviness of a fiber.
Catalyst:
A chemical which, though not part of a reaction, modifies the rate at which it takes place.
Crimp Amplitude:
The height of displacement of a fiber from its uncrimped condition.
Chemical finishing:
Changing the appearance or physical properties and performance of a fabric via chemical applications, i.e. flame retardancy, modifications in hand water or alcohol repellency, etc.
Crimp Energy:
The amount of work required to straighten a fiber.
Clump:
An irregularly shaped grouping of fibers in the web resulting from improper separation of the fibers.
Crimp Frequency:
The crimp level, or number of crimps per inch, in yarn or tow.
Coagulation:
The agglomeration of suspended particles from a dispersed state.
Crimp Percent:
The difference in the relaxed and fully extended lengths of a crimped fiber, expressed as a percentage of the extended length.
Cohesion:
The force which holds fibers together during processing. It is usually a function of lubricant (type and amount) and fiber crimp, or geometry.
Cross Direction:
The axis, within the plane of a nonwoven fabric, perpendicular to the nonwovens' motion in the final forming step (see also Machine direction [link to Machine Direction]).
Composite nonwoven:
A structure made by laminating a nonwoven fabric with another nonwoven, or other material, so as to take advantage of certain properties of each.
Cross-Linking:
The connecting together of polymer chains by chemical reaction with certain compounds, so that the chains are joined at one or more points along their length; i.e. cross-linked.
Conditioning:
A process of allowing textile materials to reach moisture equilibrium with the surrounding atmosphere. Materials may be conditioned in a standard atmosphere (65 % R.H., 70° F) for testing purposes, or in conditions existing in manufacturing or processing areas.
Cross-section:
The shape of an individual fiber when cut at right angles to its longitudinal axis. Normal shapes for man-made fibers vary (e.g. Round for nylon, polyester, polypropylene and some acrylics; Serrated or Crenular for viscose rayon, acetate and triacetate; Bean-shaped for some acrylics and modacrylics). The shapes of man-made fibers may be modified by changing the shape of the holes in the spinneret. Cross-sectional variants are produced intentionally in a wide variety of shapes for different physical effects, such as change in luster or hand, improved resistance to soiling, etc.
Contact angle:
The angle formed by a liquid resting upon the surface of a solid at the gas-solid-liquid interface. The angle is measured in the liquid, being the angle included between the surface of the solid and a plane (or line) tangent to the surface of the liquid at the gas-solid-liquid interface. Smaller contact angles indicate greater wettability of the solid.
Curing:
In finishing fabrics, a process by which resins or plastics are set in or on textile materials, usually by heating.
Cleanability: How easy the fabric is to clean.
Degradation:
Loss of desired physical properties of a fabric due to exposure to time, temperature or chemicals including atmospheric pollutants.
Doffer:
The delivery, or last, cylinder of the card from which the sheet of fibers is removed by the doffer comb.
Delamination:
Tendency of a fabric to be pulled apart (layer separation) by normal surface forces or shear tensions.
Drape:
The suppleness and ability of a fabric to form graceful configurations (not to be confused with a drapery fabric or a surgical drape).
Delustrant:
A substance that can be used to dull the luster of a fiber or fabric. Often a pigment such as titanium is used.
Dry Forming (Dry Laying):
Forming nonwovens by a dry process; for example, by mechanical means or from air dispersion.
Denier:
A weight-per-unit-length measure of any linear material. Denier is numerically equal to the weight in grams of 9,000 meters of the material.
Drying Cylinders:
Heated revolving cylinders for drying fabric or yarn. They are arranged either vertically or horizontally in sets, with the number varying according to the material to be dried.
Dispersion:
1) A distribution of finely divided particles in a medium; for example, a colloidal suspension of a substance. 2) A qualitative estimation of the separation and uniform distribution of fibers, typically in a water suspension for wet forming.
Dumbbells:
Defects common to wet-formed nonwovens in which a "long" fiber entangles clumps of "regular" fibers. Typically, clumps are found at each end of the "long" fiber, giving it the appearance of a dumbbell.
Dimensional Stability:
Stretching ability of a fabric. Generally want a fabric to retain its shape.
Terms used for Filtration Mechanisms
*Usually more than one Filtration mechanism is in effect.
Diffusion:
Particles are smaller than a fabric's pore size and random movement of the fabric will close up the pores.
Elongation:
The increase in length of a nonwoven in the direction of an applied tensile force.
Emulsion:
A finely divided suspension of one liquid in another liquid.
A process utilizing pressure to produce raised or projected figures or design; in relief in fabric surfaces.
Entanglement:
Interlocking fibers by mechanical or fluid methods that utilize friction and interlacing to provide fabric integrity.
Electrostatic Forces:
Positively charged particles stick to negatively charged fabric, or vice versa.
Felt:
A sheet of matted fibers–often wool, hair or fur–made by a combination of mechanic and chemical action, pressure, moisture and heat. The term also refers to a woven fabric generally made of wool, heavily shrunk or fulled so as to make it almost impossible to distinguish the weave.
Flame Retardancy:
The ability of a fabric to resist ignition and/ or flame propagation.
The basic element of fabrics and other textile structures characterized by having length at least 100 times its diameter or width. Natural fibers are produced from either animals (e.g. wool, silk), vegetables (e.g. cotton, flax, jute) or minerals (e.g. asbestos). Man-made fibers may be either polymers synthesized from chemical compounds (e.g. polyesters nylon, polypropylene, acrylic, vinyon, etc) or modified natural polymers (e.g. ray acetate, or minerals like glass).
Flex Abrasion:
Abrasion of a sheet or fabric resulting from unidirectional flexing, a frictional passage over a bar, or other wear surface.
Fiber Distribution:
The orientation and/ or uniformity of fibers, or blends of fiber throughout the web.
(see Continuous Filament [link to continuous filament])
Garneting:
A process for reducing textile waste materials to fiber by passing through a garnet, a machine similar to a card.
Greige Fabric:
Fabric prior to any finishing.
Grab Strength:
A measure of the "effective strength" of a fabric; i.e. the strength fibers in a specific width together with the additional strength contributed by ajar fibers. Typically, grab strength is determined on a four-inch-wide fabric strip, with tensile load applied at the midpoint of the fabric width through one-inch-wide faces that are used to clamp the fabric.
Hand:
The tactile qualities of a fabric, e.g. softness, firmness, elasticity, fineness, resilience and other qualities perceived by touch.
Hydration:
The incorporation of molecular water into a complex molecule with molecules or units of another species.
Small perforations or opening of varying sizes in a fabric.
Hydrophilic:
Having strong affinity for, or the ability to absorb, water.
Hot-Melt Adhesive:
A solid material that melts quickly upon heating then sets a firm bond upon cooling. Used for almost instantaneous bonding
Hydrophobic:
Lacking affinity for, or the ability to absorb, water.
Heat Resistance:
How well a fabric stands up to high temperatures.
Isotropic:
Exhibiting the same physical properties in every direction; generally applied to nonwoven fabrics in which fibers are oriented in a random manner.
Impaction:
When the particle is larger than the fabric's pore, causing a blockage.
Inteseption:
Particle size is equal to the size of the fabric's pore, with some particles able to squeeze through.
Man-Made Fiber:
See Fiber
Mechanical Finishing:
Changing the appearance or physical characteristics of a fabric via mechanical processes, i.e. napping, calendering, embossing, compacting, brushing, etc.
Mildew Resistance:
The degree to which fabrics are unaffected by mildew or mold.
Machine Direction:
The axis parallel to the nonwovens motion in the final forming step and within the plane of the substance (also see Cross Direction).
Mildew:
A growth caused by spore-forming fungi that grow under warm, moist conditions. The presence of mildew may result in discoloration, tendering or variation in dyeing properties in cellulosic fibers.
Mechanical Strength:
How well a fabric can handle the 'pulse' of the collector.
Natural Fibers:
(see Fiber)
Neps:
Small fiber balls which were not opened prior to web formation.
Needle Stitching:
Sewing webs of fiber together with multi-needle equipment to bind the webs into a fabric.
Nonwoven Fabric:
A fabric made directly from a web of fiber without the yarn preparation necessary for weaving and knitting. In a nonwoven, the assembly of textile fibers is held together 1) by mechanical interlocking in a random web or mat; 2) by fusing of the fibers, in the case of thermoplastic fibers; or 3) by bonding with a cementing medium such as starch, casein, rubber latex, a cellulose derivative or synthetic resin. Initially, the fibers may be oriented in one direction or may be deposited in a random manner. This web or sheet is then bonded together by one of the methods described above. Fiber lengths can range from 0.25 inch to 6 inches for crimped fibers, up to continuous filament in spun bonded fabrics.
Needle Punching:
Subjecting a web of fibers to repeated entry of barbed needles that compact and entangle individual fibers to form a fabric
1) A preliminary operation in the processing of staple fiber designed to separate the compressed masses of staple into loose tufts and to remove the heavier impurities;
2) An operation in the processing of tow that substantially increases the bulk of the tow by separating the filaments and deregistering the crimp.
Permeability:
A measure of the state or quality of being penetrable by fluids or gases
The action of a solid or liquid separating from a solution because of a chemical or physical process, or change that has rendered it insoluble.
Picker:
A machine that opens staple fiber and forms a lap for the carding process.
Print Bonding:
Binding groups of fibers into a fabric by applying adhesive in a discrete pattern.
Pilling:
The tendency of fibers to mat or ball together on the surface of a fabric.
Pulp:
The end product of cooking wood chips, cotton or some other source of cellulose with water and appropriate chemicals. Used in the manufacture of cellulosic fibers, absorbent padding, other cellulose-based products and wet-formed nonwoven fabrics.
Point Bonding:
Binding thermoplastic fibers into a fabric by applying heat and pressure to form fiber bonds in a discrete pattern of points.
How open the cloth is, which determines how fast the air will go through the fabric.
Pressure Drop:
A lower CFM reading means high pressure. You must avoid a high pressure drop
Saturation Bonding:
Binding fibers into a fabric by saturating the web with an adhesive mixture.
Staple Fibers:
Natural fibers or cut lengths from continuous filaments.
Seaming:
Joining of two pieces of fabric, generally near an edge.
An accumulation of negative or positive electrical charges on the surface of fibers or fabrics resulting from inadequate electrical dissipation during processing. Static results in an electrical attraction or repulsion of the fibers relative to themselves, to machine parts or to other materials, preventing the fiber from traveling in a normal path in the process.
Seam Strength:
The ability of a fabric to hold a seam against tension.
Stiffness:
The ability of a fabric to resist bending when flexural stress is applied.
Short Fiber:
Typically used to describe the length of fibers used in wet-forming processes by the textile industry; generally refers to individual staple fibers less than 0.75-inch in length.
The ability of a fabric to extend in length when stress is applied
Shrinkage:
A reduction in dimensions, as from heat, wetting or chemical action.
Fabric destined to be used for subsequent processing or in combination with other coatings or fabrics.
Splinters:
Two or more staple fibers adhering together, causing a stiff cluster which resists pulling apart in normal processing and reacting similarly to higher-than-normal denier fiber.
Super Absorbency:
The ability of a material to absorb many times its own weight in fluids.
Spray Bonding:
Application of a nonwoven binder by spraying.
Surface Charge:
The electrical charge on the surface of a fabric or fiber.
Spunbonded Fabric:
A fabric formed by filaments that have been extruded, drawn, laid on a continuous belt, and then immediately bonded.
Surface Energy:
The work necessary to increase the surface area of a liquid (generally expressed in dynes per unit area).
Spunlaced Fabric:
A fabric formed of fibers entangled in a predetermined repeating pattern to form a strong structure free of binder.
Surface Tension:
A property of liquid surfaces whereby the liquid surface tends to contract to a minimum. Generally, whenever two dissimilar substances make contact at an interface, the inequalities of molecular attraction, together with other forces in action, tend to change the shape of the interface until the potential energy of the whole molecular system attains a minimum value.
Tear Strength:
Resistance of a fabric to a tearing action.
A weight-per-unit length measure of a fiber or other lineal material. Tex is numerically equal to the weight in grams of one kilometer of the material
Tenacity:
Tensile stress, when expressed as force per unit linear density of the unstrained.
Textile:
Originally a woven fabric. Now applied as a general term to fibers, yarn or fabrics.
Tensile Strength:
The strength shown by a fabric subjected to tension as distinct from torsion, compression or shear.
The dimension of a sheet or lamina measured perpendicular to the plane of the sheet.
Unidirectional:
Performing best in only one direction; generally applied to nonwovens in which fabric strength is highly oriented in the direction of web travel through the forming process.
Wash-Wear Properties:
The ability of a fabric to retain its strength and/or appearance after repeated machine washings and tumble drying.
Horizontal edge-to-edge measurement of a fabric in a relaxed condition on a flat surface.
The mass of a fabric expressed in grams per square meter or ounces per square yard.
Work Energy:
The energy required to elongate and totally rupture a fabric, causing ultimate failure.
Wet Forming (Wet Laying):
Deposition of a web from an aqueous suspension of fibers.
Wrinkle Resistance:
The ability of a fabric to shed creases, both dry or wet, after it has been compressed.
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