Fibers

 

Fiber or fibre (British English; from Latin: fibra ) is a natural or artificial substance that is significantly longer than it is wide.Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.

Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can give some benefits, such as comfort, over their synthetic counterparts.

Natural Fibers

Natural fibers develop or occur in the fiber shape, and include those produced by plants, animals, and geological processes.They can be classified according to their origin:

• Vegetable fibers are generally based on arrangements of cellulose, often with lignin: examples include cotton, hemp, jute, flax, abaca, piña, ramie, sisal, bagasse, and banana. Plant fibers are employed in the manufacture of paper and textile (cloth), and dietary fiber is an important component of human nutrition.
• Wood fiber, distinguished from vegetable fiber, is from tree sources. Forms include groundwood, lacebark, thermomechanical pulp (TMP), and bleached or unbleached kraft or sulfite pulps. Kraft and sulfite refer to the type of pulping process used to remove the lignin bonding the original wood structure, thus freeing the fibers for use in paper and engineered wood products such as fiberboard.
• Animal fibers consist largely of particular proteins. Instances are silkworm silk, spider silk, sinew, catgut, wool, sea silk and hair such as cashmere wool, mohair and angora, fur such as sheepskin, rabbit, mink, fox, beaver, etc.
• Mineral fibers include the asbestos group. Asbestos is the only naturally occurring long mineral fiber. Six minerals have been classified as "asbestos" including chrysotile of the serpentine class and those belonging to the amphibole class: amosite, crocidolite, tremolite, anthophyllite and actinolite. Short, fiber-like minerals include wollastonite and palygorskite.
• Biological fibers, also known as fibrous proteins or protein filaments, consist largely of biologically relevant and biologically very important proteins, in which mutations or other genetic defects can lead to severe diseases. Instances include the collagen family of proteins, tendons, muscle proteins like actin, cell proteins like microtubules  and many others, such as spider silk, sinew, and hair.

Artificial fibers

Artificial or chemical fibers are fibers whose chemical composition, structure, and properties are significantly modified during the manufacturing process. In fashion, a fiber is a long and thin strand or thread of material that can be knit or woven into a fabric. Artificial fibers consist of regenerated fibers and synthetic fibers.

See also: fiber modification

Semi-synthetic fibers

Semi-synthetic fibers are made from raw materials with naturally long-chain polymer structure and are only modified and partially degraded by chemical processes, in contrast to completely synthetic fibers such as nylon (polyamide) or dacron (polyester), which the chemist synthesizes from low-molecular weight compounds by polymerization (chain-building) reactions. The earliest semi-synthetic fiber is the cellulose regenerated fiber, rayon.Most semi-synthetic fibers are cellulose regenerated fibers.

Cellulose regenerated fibers

Cellulose fibers are a subset of artificial fibers, regenerated from natural cellulose. The cellulose comes from various sources: rayon from tree wood fiber, bamboo fiber from bamboo, seacell from seaweed, etc. In the production of these fibers, the cellulose is reduced to a fairly pure form as a viscous mass and formed into fibers by extrusion through spinnerets. Therefore, the manufacturing process leaves few characteristics distinctive of the natural source material in the finished products.

Some examples of this fiber type are:

• rayon
• Lyocell, a brand of rayon
• Modal
• diacetate fiber
• triacetate fiber.

Historically, cellulose diacetate and -triacetate were classified under the term rayon, but are now considered distinct materials.

Synthetic fibers

Main article: Synthetic fiber

Synthetic come entirely from synthetic materials such as petrochemicals, unlike those artificial fibers derived from such natural substances as cellulose or protein.

Fiber classification in reinforced plastics falls into two classes: (i) short fibers, also known as discontinuous fibers, with a general aspect ratio (defined as the ratio of fiber length to diameter) between 20 and 60, and (ii) long fibers, also known as continuous fibers, the general aspect ratio is between 200 and 500.

Metallic fibers

Main article: Metallic fiber

Metallic fibers can be drawn from ductile metals such as copper, gold or silver and extruded or deposited from more brittle ones, such as nickel, aluminum or iron.

Carbon fiber

Carbon fibers are often based on oxidized and via pyrolysis carbonized polymers like PAN, but the end product is almost pure carbon.

Silicon carbide fiber

Silicon carbide fibers, where the basic polymers are not hydrocarbons but polymers, where about 50% of the carbon atoms are replaced by silicon atoms, so-called poly-carbo-silanes. The pyrolysis yields an amorphous silicon carbide, including mostly other elements like oxygen, titanium, or aluminium, but with mechanical properties very similar to those of carbon fibers.

Fiberglass

See also: Glass § Fibreglass

Fiberglass, made from specific glass, and optical fiber, made from purified natural quartz, are also artificial fibers that come from natural raw materials, silica fiber, made from sodium silicate (water glass) and basalt fiber made from melted basalt.

Mineral fibers

Mineral fibers can be particularly strong because they are formed with a low number of surface defects; asbestos is a common one.

Polymer fibers

• Polymer fibers are a subset of artificial fibers, which are based on synthetic chemicals (often from petrochemical sources) rather than arising from natural materials by a purely physical process. These fibers are made from:
• polyamide nylon
• PET or PBT polyester
• phenol-formaldehyde (PF)
• polyvinyl chloride fiber (PVC) vinyon
• polyolefins (PP and PE) olefin fiber
• acrylic polyesters, pure polyester PAN fibers are used to make carbon fiber by roasting them in a low oxygen environment. Traditional acrylic fiber is used more often as a synthetic replacement for wool. Carbon fibers and PF fibers are noted as two resin-based fibers that are not thermoplastic, most others can be melted.
• aromatic polyamids (aramids) such as Twaron, Kevlar and Nomex thermally degrade at high temperatures and do not melt. These fibers have strong bonding between polymer chains
• polyethylene (PE), eventually with extremely long chains / HMPE (e.g. Dyneema or Spectra).
• Elastomers can even be used, e.g. spandex although urethane fibers are starting to replace spandex technology.
• polyurethane fiber
• Elastolefin
• Coextruded fibers have two distinct polymers forming the fiber, usually as a core-sheath or side by side. Coated fibers exist such as nickel-coated to provide static elimination, silver-coated to provide anti-bacterial properties and aluminum-coated to provide RF deflection for radar chaff. Radar chaff is actually a spool of continuous glass tow that has been aluminum coated. An aircraft-mounted high speed cutter chops it up as it spews from a moving aircraft to confuse radar signals.

Microfibers

Invented in Japan in the early 1980s, microfibers are also known as microdenier fibers. Acrylic, nylon, polyester, lyocell and rayon can be produced as microfibers. In 1986, Hoechst A.G. of Germany produced microfiber in Europe. This fiber made it way into the United States in 1990 by DuPont.

Microfibers in textiles refer to sub-denier fiber (such as polyester drawn to 0.5 denier). Denier and Dtex are two measurements of fiber yield based on weight and length. If the fiber density is known, you also have a fiber diameter, otherwise it is simpler to measure diameters in micrometers. Microfibers in technical fibers refer to ultra-fine fibers (glass or meltblown thermoplastics) often used in filtration. Newer fiber designs include extruding fiber that splits into multiple finer fibers. Most synthetic fibers are round in cross-section, but special designs can be hollow, oval, star-shaped or trilobal. The latter design provides more optically reflective properties. Synthetic textile fibers are often crimped to provide bulk in a woven, non woven or knitted structure. Fiber surfaces can also be dull or bright. Dull surfaces reflect more light while bright tends to transmit light and make the fiber more transparent.

Very short and/or irregular fibers have been called fibrils. Natural cellulose, such as cotton or bleached kraft, show smaller fibrils jutting out and away from the main fiber structure.

Weaving is a method of textile production in which two distinct sets of yarns or threads are interlaced at right angles to form a fabric or cloth. Other methods are knitting, crocheting, felting, and braiding or plaiting. The longitudinal threads are called the warp and the lateral threads are the weft, woof, or filling. The method in which these threads are interwoven affects the characteristics of the cloth. Cloth is usually woven on a loom, a device that holds the warp threads in place while filling threads are woven through them. A fabric band that meets this definition of cloth (warp threads with a weft thread winding between) can also be made using other methods, including tablet weaving, back strap loom, or other techniques that can be done without looms.

The way the warp and filling threads interlace with each other is called the weave. The majority of woven products are created with one of three basic weaves: plain weave, satin weave, or twill weave. Woven cloth can be plain or classic (in one colour or a simple pattern), or can be woven in decorative or artistic design.

Process and terminology

In general, weaving involves using a loom to interlace two sets of threads at right angles to each other: the warp which runs longitudinally and the weft (older woof) that crosses it. (Weft is an Old English word meaning "that which is woven"; compare leave and left.) One warp thread is called an end and one weft thread is called a pick. The warp threads are held taut and in parallel to each other, typically in a loom. There are many types of looms.

Weaving can be summarized as a repetition of these three actions, also called the primary motions of the loom.

• Shedding: where the warp threads (ends) are separated by raising or lowering heald frames (heddles) to form a clear space where the pick can pass
• Picking: where the weft or pick is propelled across the loom by hand, an air-jet, a rapier or a shuttle
• Beating-up or battening: where the weft is pushed up against the fell of the cloth by the reed

The warp is divided into two overlapping groups, or lines (most often adjacent threads belonging to the opposite group) that run in two planes, one above another, so the shuttle can be passed between them in a straight motion. Then, the upper group is lowered by the loom mechanism, and the lower group is raised (shedding), allowing the shuttle to pass in the opposite direction, also in a straight motion. Repeating these actions forms a fabric mesh but without beating-up, the final distance between the adjacent wefts would be irregular and far too large.

The secondary motions of the loom are the:

• Let off motion: where the warp is let off the warp beam at a regulated speed to make the filling even and of the required design
• Take up motion: takes up the woven fabric in a regulated manner so that the density of filling is maintained

The tertiary motions of the loom are the stop motions: to stop the loom in the event of a thread break. The two main stop motions are the

• Warp stop motion
• Weft stop motion

The principal parts of a loom are the frame, the warp-beam or weavers beam, the cloth-roll (apron bar), the heddles, and their mounting, the reed. The warp-beam is a wooden or metal cylinder on the back of the loom on which the warp is delivered. The threads of the warp extend in parallel order from the warp-beam to the front of the loom where they are attached to the cloth-roll. Each thread or group of threads of the warp passes through an opening (eye) in a heddle. The warp threads are separated by the heddles into two or more groups, each controlled and automatically drawn up and down by the motion of the heddles. In the case of small patterns the movement of the heddles is controlled by "cams" which move up the heddles by means of a frame called a harness; in larger patterns the heddles are controlled by a dobby mechanism, where the healds are raised according to pegs inserted into a revolving drum. Where a complex design is required, the healds are raised by harness cords attached to a Jacquard machine. Every time the harness (the heddles) moves up or down, an opening (shed) is made between the threads of warp, through which the pick is inserted. Traditionally the weft thread is inserted by a shuttle.

On a conventional loom, continuous weft thread is carried on a pirn, in a shuttle that passes through the shed. A handloom weaver could propel the shuttle by throwing it from side to side with the aid of a picking stick. The "picking" on a power loom is done by rapidly hitting the shuttle from each side using an overpick or underpick mechanism controlled by cams 80–250 times a minute. When a pirn is depleted, it is ejected from the shuttle and replaced with the next pirn held in a battery attached to the loom. Multiple shuttle boxes allow more than one shuttle to be used. Each can carry a different colour which allows banding across the loom.

Weaving pattern cards used by Skye Weavers, Isle of Skye, Scotland

The rapier-type weaving machines do not have shuttles, they propel cut lengths of weft by means of small grippers or rapiers that pick up the filling thread and carry it halfway across the loom where another rapier picks it up and pulls it the rest of the way.Some carry the filling yarns across the loom at rates in excess of 2,000 metres per minute. Manufacturers such as Picanol have reduced the mechanical adjustments to a minimum, and control all the functions through a computer with a graphical user interface. Other types use compressed air to insert the pick. They are all fast, versatile and quiet.

The warp is sized in a starch mixture for smoother running. The loom warped (loomed or dressed) by passing the sized warp threads through two or more heddles attached to harnesses. The power weavers loom is warped by separate workers. Most looms used for industrial purposes have a machine that ties new warps threads to the waste of previously used warps threads, while still on the loom, then an operator rolls the old and new threads back on the warp beam. The harnesses are controlled by cams, dobbies or a Jacquard head.

A 3/1 twill weave, as used in denim

The raising and lowering sequence of warp threads in various sequences gives rise to many possible weave structures:

• Plain weave: plain, and hopsacks, poplin, taffeta,poult-de-soie, pibiones and grosgrain
• Twill weave: these are described by weft float followed by warp float, arranged to give diagonal pattern; examples are 2/1 twill, 3/3 twill, or 1/2 twill. These are softer fabrics than plain weaves.
• Satin weave: satins and sateens
• Complex computer-generated interlacings, such as Jacquard fabric
• Pile fabrics: fabrics with a surface of cut threads (a pile), such as velvets and velveteens
• Selvage refers to the fabric's edge, which may be marked with the manufacturer's detail. It is a narrow edge of a woven fabric parallel to its length.
• Thrums are the remainder yarns for tying on the loom. The portion that is not weavable warp. It is also called loom waste.

Both warp and weft can be visible in the final product. By spacing the warp more closely, it can completely cover the weft that binds it, giving a warp faced textile such as repp weave. Conversely, if the warp is spread out, the weft can slide down and completely cover the warp, giving a weft faced textile, such as a tapestry or a Kilim rug. There are a variety of loom styles for hand weaving and tapestry.

Archaeology

There are some indications that weaving was already known in the Paleolithic Era, as early as 27,000 years ago. An indistinct textile impression has been found at the Dolní Věstonice site.According to the find, the weavers of the Upper Palaeolithic were manufacturing a variety of cordage types, produced plaited basketry and sophisticated twined and plain woven cloth. The artifacts include imprints in clay and burned remnants of cloth.

The oldest known textiles found in the Americas are remnants of six finely woven textiles and cordage found in Guitarrero Cave, Peru. The weavings, made from plant fibres, are dated between 10,100 and 9080 BCE.

In 2013 a piece of cloth woven from hemp was found in burial F. 7121 at the Çatalhöyük site,suggested to be from around 7000 BCE Further finds come from the Neolithic civilisation preserved in the pile dwellings in Switzerland.

Another extant fragment from the Neolithic was found in Fayum, at a site dated to about 5000 BCE.This fragment is woven at about 12 threads by 9 threads per centimetre in a plain weave. Flax was the predominant fibre in Egypt at this time (3600 BCE) and had continued popularity in the Nile Valley, though wool became the primary fibre used in other cultures around 2000 BCE.^{[citation needed]}.

The oldest-known weavings in North America come from the Windover Archaeological Site in Florida. Dating from 4900 to 6500 BCE and made from plant fibres, the Windover hunter-gatherers produced "finely crafted" twined and plain weave textiles.Eighty-seven pieces of fabric were found associated with 37 burials.^{[citation needed]} Researchers have identified seven different weaves in the fabric.^{[citation needed]} One kind of fabric had 26 strands per inch (10 strands per centimetre). There were also weaves using two-strand and three-strand wefts. A round bag made from twine was found, as well as matting. The yarn was probably made from palm leaves. Cabbage palm, saw palmetto and scrub palmetto are all common in the area, and would have been so 8,000 years ago.

Evidence of weaving as a commercial household industry in the historical region of Macedonia has been found at the Olynthus site. When the city was destroyed by Philip II in 348 BCE, artifacts were preserved in the houses. Loomweights were found in many houses, enough to produce cloth to meet the needs of the household, but some of the houses contained more loomweights, enough for commercial production, and one of the houses was adjacent to the agora and contained three shops where many coins were found. It is probable that such homes were engaged in commercial textile manufacture.

History

Weaving was known in all the great civilisations, but no clear line of causality has been established. Early looms required two people to create the shed and one person to pass through the filling. Early looms wove a fixed length of cloth, but later ones allowed warp to be wound out as the fell progressed. Weaving became simpler when the warp was sized.