Textile Fibers – the building blocks of the textile industry

Properties of Fibers

Introduction of Fibers

• Fiber is an individual, fine, hairlike structure.
• Fibers have a comparatively high ratio of length to width, thus ensuring the flexibility required for manufacturing and end use.
• Differences among the textile fibers result from their different chemical compositions, the arrangement of their molecules, and their external features (e.g., shape).
• Fibers usually are grouped and twisted together into continuous strands called yarns. The yarns are then used to make various textile materials (e.g., woven fabrics, knitted fabrics, lace).
• Fibers can also be used directly to make a fabric without first being made into yarns. Felt and nonwoven materials (e.g. interfacing) are two examples of fabrics made directly from fibers.

Sources

Fibers are classified into those found in nature, called natural fibers, or those that are manufactured through the use of science and technology. Manufactured fibers are designed to resolve particular problems and answer specific needs.

Natural Fibers

• Natural fibers are obtained from plants or animals. Plant fibers may come from stems (e.g., flax, hemp, jute, ramie), leaves (e.g., sisal, abaca), or seeds (e.g, cotton, kapok) of plants.
• Animal fibers (e.g., wool, cashmere, mohair, vicuna) protect people against the cold the same as they do animals. Silk is considered an animal fiber, although it comes from the cocoon of a silkworm rather than a mammal’s fur.

Manufactured Fibers

• Manufactured, or man-made, fibers are made from chemical solutions that are forced through tiny holes, similar to water passing through a showerhead.
• The device used to form the filaments is called a spinnerette. It can be as small as a thimble or as large as a plate, with tiny holes on the top or flat surface area.
• The fine liquid streams of solution that are forced through the holes are hardened into continuous strands called filament fibers. This action is copied from nature. The silkworm extrudes streams of silk liquid, which harden into filaments on contact with the air.
• The number of holes in the spinnerette, as well as their shape and their size, varies according to the filament fiber and yarn desired. A small spinnerette has as few as 10 holes, and a large one can have more than 10,000.

Different techniques are used to harden the liquid streams and produce the filament fibers. The technique used depends on the chemical composition of the solution.

The more commonly used methods are :

• Dry spinning
• Wet spinning
• Melt spinning

Dry spinning method

The fiber solution, mixed with a solvent, is forced through the spinnerette into warm air. The warm air helps evaporate the solvent, and the liquid stream then hardens. Acetate and modacrylic fibers are made in this manner.

Wet spinning method

The solution is forced through the spinnerette and then into a liquid solution in which the fiber solution streams harden into continuous filaments. Acrylic fibers well as viscose rayon fibers are made with this method.

Melt spinning method

The solid material is melted to form a liquid solution that is forced through the spinnerette and into cool air, where the liquid fiber streams harden into continuous filaments. Glass, nylon, polyester, and olefin fibers are made in this way.

Fiber Length

• Fibers vary from less than one inch to miles in length. Fibers whose lengths are measured in inches are called staple fibers.
• Fibers of longer lengths are called filament fibers.
• Silk is the only natural fiber that is found in filament form. It is usually about 1,600 yards (1,463 m) long.
• All the other natural fibers vary in length, from about ½ inch to 36 inches.
• Cotton is usually ½ to 2 ½ inches, flax is usually 2 to 36 inches, and wool is usually 1 to 18 inches.
• All manufactured fibers are produced originally as filament fibers. Sometimes they remain as such, but often they are made into shorter-length staple fibers from 1 ½ to 6 ½ inches. The process frequently involves crimping the filament fibers and then heat-setting to maintain the crimp configuration.
• Thousands of the filaments are sometimes grouped to form a thick rope called tow and are then cut or broken into the required lengths before being twisted into yarns.
• Some manufactured fibers, such as spandex, are always used as filament fibers.
• Other manufactured fibers, such as acrylic for apparel, are almost always made into staple fibers.
• When making filaments that are later to be cut into short pieces, large spinnerettes with many holes are used in order to obtain high production. Small spinnerettes are used when making filaments for filament yarns because the number of holes in the spinnerette must equal the number of filament fibers that the particular filament yarn will contain.
• This is a basic reason why staple fibers are less expensive per pound than comparable filament fibers.

Fiber Shape

• When viewed with the naked eye, all fibers look very similar. When viewed under a microscope, however, fibers varying configurations are visible.
• The microscopic cross-sectional shape of the fiber and the surface construction determine the bulk, texture, luster, and hand of the fiber.
• Fiber’s cross-sectional shape influences the way light is reflected from the surface.
• A flat-surfaced fiber has more luster than a round one. A round fiber reflects light in one general direction. A multilobal-shaped fiber tends to scatter the light, causing a diffuse glow with sparkles (glitter).
• The sparkles are caused by bright spots from the light reflected from the tips of the rounded lobes.
• An irregular cross-section scatters light in many directions, resulting in a dullish appearance with few highlights.
• Round fibers, such as wool, result in bulkier fabrics because they do not pack as much as flat fibers, such as cotton.
• Round-shaped, rodlike fibers, such as nylon, offer a smoother, more slippery hand than wool, which has a round shape but a scaly surface.

Fiber Surfaces

• The surfaces of fibers vary. For example, they can be smooth, rough, slightly grooved, deeply channeled, or wrinkled.
• Wool fiber is scaly, cotton is smooth, and rayon is serrated. The fiber surface affects such properties as hand, lustre, and wicking.

Fiber Longitudinal Configuration

• Lengthwise, fibers have varying configurations. They may be straight, twisted, coiled, or crimped. Cotton fiber, for example, is naturally twisted, whereas nylon fiber is fairly straight.
• Various performance properties – such as resiliency, elasticity, and abrasion resistance – are affected by fiber longitudinal configuration.
• Crimp refers to the bends and twists along the length of a fiber. Greater crimp increases resiliency, bulk, warmth, elongation, absorbency, and skin comfort.
• However, the hand becomes harsher and lustre is reduced as crimp increases. Crimp allows the fiber to stand off the skin so the fabric will not cling to the wearer’s skin.
• Crimp is inherent in wool fibers. Although it is not inherent in manufactured fibers. Crimp can also be added after the yarn has been produced by a process called texturing.

Fiber Diameter

• Fiber diameter refers to the thickness of the fiber.
• Thicker fibers result in greater stiffness, which improves wrinkle resistance but can also result in undesirable roughness.
• Large-diameter fibers result in bulkier fabrics because they do not pack as well as thin fibers. Fine-diameter fibers can result in a fabric that is sheer, light-weight, and generally more drapable and softer to the touch than the fabric of thicker fibers.
• The size the diameter of natural fibers varies depending on fiber type.
• Natural fibers grow irregularly and do not have uniformity along the length. Manufactured fibers are uniform in length and are available in a range of fiber diameters controlled by the producer

 Chemical Composition and Molecular Formation

• Fibers are classified into various groups by their chemical composition. Fibers with similar chemical makeup are placed in the same category. Cotton and flax are placed in the same category—cellulosic fiber—because both are natural cellulose. Cotton, wool, and polyester, however, are each in a different category—cellulosic, protein, and synthetic, respectively.
• Although fibers in the same category have similar properties, they can also have different properties. For example, polyester and acrylic synthetic fibers are both resilient (wrinkle resistant), but the polyester fiber is much stronger than acrylic fiber.
• Furthermore, although each group of fibers has different properties from fibers in another group, there may be some similar properties. For example, although cotton and acetate fibers are in different groups (cellulose and synthetic), each is hydrophilic (i.e., absorbs water easily).
• A fibers chemical composition relates to its reaction to various items, such as bleaches, sunlight, moths, mildew, flame, and perspiration. It also determines whether the fiber is a thermoplastic (able to be melted), which dyes can be used to color it, and its reaction to chemical finishes.
• The arrangement of the molecules within a fiber affects its strength, abrasion resistance, and resiliency.
• With natural fibers, little modification is possible, but with manufactured fibers, modifications are possible within limits determined by the chemical structure.
• This has allowed the development of numerous variations of manufactured fibers through the application of textile science and technology.

Fiber Performance properties

Fiber performance properties determine the behavior characteristics of fibers and thus their suitability in specific use conditions.

Standardized tests and laboratory procedures are used to measure and compare fiber properties, which can be categorized into four groupings – aesthetics, durability, comfort, and safety.

Aesthetics

Flexibility

• Flexibility is the capability of fiber to bend easily and repeatedly without breaking. A flexible fiber such as acetate can be made into a highly drapable fabric and garment. A rigid fiber such as glass, which is not used in apparel but can be found in draperies, usually makes a fabric that is relatively stiff.
• Usually the thinner the fiber, the better its capability. Flexibility also influences the hand of a material.
• Although a highly drapable fabric is often desired, there are also times when a more rigid fabric is wanted. For example, in a swing coat (a coat that hangs from the shoulders and flares out), a more rigid fabric is needed to produce the desired shape.

Hand

• The hand is the way a fiber, yarn, or fabric feels when handled. The hand of the fiber is affected by its shape, surface, and configuration.
• Fiber shapes vary and include round, flat, and multimodal.
• Fiber surfaces also vary having attributes such as smooth, serrated, or scaly.
• The fiber configuration is either crimped or straight. The type of yarn, fabric construction and finishing processes used also affect the hand of a fabric.
• Terms such as soft, crisp, dry, silky, stiff, boardy, or harsh are used to describe the hand of a textile material.

Luster

• Luster refers to the light reflected from a surface.
• Increased light reflection occurs from a smoother surface, less crimp, flatter cross-sectional shape, and longer fiber length. The drawing process used in producing manufactured fibers increases the amount of luster by making the surface smoother.
• The addition of declustering agents breaks up the reflected light so less luster occurs. Thus, by controlling the number of delusterants added, we can make manufactured fibers bright, semi-dull, or dull.
• Fabric luster is also affected by the yarn type, weave, and finish used. The desired amount of luster depends on fashion trends and customer desires.

Pilling

• Pilling is the formation of groups of short or broken fibers on the surface of a fabric that is tangled together in the shape of a tiny ball called a pill. They are formed when the ends of a fiber break from the fabric surface, usually from wear.
• Pilling is not a desirable property because it makes fabrics look worn and unsightly and feel less comfortable, such as when formed on sheets. The pills usually form in areas that are rubbed, such as collars, along the underside of sleeves and at the edges of cuffs.
• Hydrophobic fibers tend to pill much more than hydrophilic fibers because hydrophobic fibers have a greater electrical static attraction for each other and do not fall off the fabric surface.
• Wool, although hydrophilic, pills because of its scaly surface. The fibers snag each other, tangle, and form a pill.

Resiliency

• Resiliency is the capability of a material to spring back to shape after being creased, twisted, or distorted. It is closely connected with wrinkle recovery.
• A fabric that has good resiliency does not wrinkle easily and therefore, tends to retain its good appearance.
• Thicker fibers possess greater resiliency because there is more mass to absorb the strain. Also, fiber shape affects fiber resiliency; round fibers usually possess greater resiliency than flat fibers.
• Polyester has outstanding resiliency; cotton has poor resiliency.
• A resilient fiber creates a problem if a sharp crease is desired in a garment. It is easy to make a sharp crease on a cotton or rayon fabric, but not on a dry-wool material.

Specific Gravity

• Specific gravity is the ratio of the mass of the fiber to an equal volume of water at 4°C.
• A lightweight fiber enables the fabric to be warm without being heavy.
• Fabric can be made thick and lofty and still remain relatively lightweight.
• Acrylic fiber is an excellent example. It is much lighter weight than wool, but it has wool-like properties and so is used extensively to make lightweight-yet-warm blankets, scarves, heavy socks, and other winter-wear items.

Static Electricity

• Static electricity is a fractional electric charge caused by the rubbing together of two dissimilar materials. The effects, such as clothes clinging to the wearer or lint being attracted to the fabric, occur when the electric charge is retained and builds up on the surface.
• A spark or shock occurs when the surface comes in contact with a good conductor and there is a rapid discharge.
• Moisture contained in fibers acts as a conductor to remove the charge and prevent the previously mentioned effects from occurring. Hydrophobic fibers, because they contain very little moisture, are prone to static electricity.
• Static can also occur with natural fibers, but only if they are very dry, in which case they act as if they are hydrophobic. Fabrics containing epitopic fibers (fibers that conduct electricity) have no static problems.

Thermoplasticity

• A thermoplastic fiber softens when heat is applied and may melt to a liquid state when higher heat is applied. Many manufactured fibers are thermoplastic.
• Permanent creases and pleats can be made on fabrics containing thermoplastic fibers by applying enough heat to create a crease or pleat but not enough to melt the fiber; when the heat is removed, the crease or pleat is permanently set.
• The creases are permanent until a higher temperature is applied to negate the heat-setting effect. The shape can also be imparted to garments by this process, giving thermoplastic fabrics good dimensional stability.
• Fiber thermoplasticity is an important property that makes many textile innovations possible. Examples are textured yarns, permanent embossing, durable press, and others. Shaped hat bodies and bra cups are also examples of applications of thermoplastic fibers.

Durability

Abrasion Resistance

• Abrasion resistance is the ability to resist wear from rubbing that contributes to fabric durability.
• Garments made from fibers that possess both high breaking strength and abrasion resistance can be worn often and for a long period of time before signs of physical wear appear.
• Nylon is used extensively in action outerwear, such as jackets and soccer shorts because it is very strong and resists abrasion extremely well.
• Acetate is often used for linings in coats and jackets because of its excellent durability and low cost.
• However, because of acetate’s poor resistance to abrasion, the lining of a jacket can fray or develop a hole long before the outer fabric shows substantial signs of wear.

Chemical Effects

• Fibers usually come into contact with chemicals either during textile processing (e.g., dyeing, finishing) or during home/professional care or cleaning (e.g. contact with soaps, bleach, and dry-cleaning solvent).
• The type of chemical, its strength, and time of exposure determine the effect on the fiber.
• Fibers react to chemicals in different ways. For example, cotton fibers have a relatively low resistance to acids but excellent resistance to alkalies, in addition, cotton fabric loses appreciable strength when finished with resin chemicals, which are used to create permanent press.

Environmental Conditions

The effects of environmental conditions on fibers vary.

The following are some examples:

• Wool garments need to be mothproofed when stored because they are susceptible to damage by these wool-eating insects.
• Nylon and silk show strength losses from extended exposure to sunlight. Therefore, they are normally not used for window treatments.
• Cotton has poor resistance to mildew and should not be allowed to remain wet for long periods of time.

Strength

• Strength is a fiber‘s ability to withstand stress.
• Fiber strength, the force needed to break the fiber, is known as tenacity and expressed in grams per denier or grains per fiber weight.
• Some fibers, such as glass, nylon, and polyester, are very strong, whereas others, such as acetate and acrylic, are weak.
• Like abrasion resistance, strength contributes greatly to fabric durability.
• Performance fabrics, as they are called, are used in outerwear, uniforms, tires, parachutes, and other end-use applications where strength is critical.

Comfort

Absorbency

• Absorbency is the ability to take in moisture. It is usually expressed as a percentage of moisture regain, which is the amount of water a dry fiber absorbs from the air under standard conditions of 70°F ( 21°C ) and 65 percent relative humidity.
• Fibers able to absorb water easily are called hydrophilic fibers. All the natural animal and vegetable fibers are hydrophilic, as are three of the manufactured fibers, rayon, lyocell, and acetate.
• Fibers that have difficulty absorbing water and are only able to absorb small amounts are called hydrophobic fibers. All the manufactured fibers besides rayon, lyocell, and acetate are hydrophobic.

Cover

• The cover is the ability to occupy an area. A thick fiber or one with crimp or curl gives fabric better covet than a thin, straight fiber.
• The fabric is warm and looks and feels substantial, but requires fewer fibers to be made.
• Wool is a widely used fiber for cold-weather garments because its crimp gives excellent cover, resulting in a large amount of air being trapped in the fabric.
• These “dead air” spaces provide insulation against the cold. The effectiveness with which fibers cover an area depends on the cross-sectional shape, longitudinal configuration, and weight.

Elasticity

• Elasticity is the ability to increase in length when under tension (elongation) and then return to the original length when released (recovery).
• Stretch and recovery when tension is placed on the fiber or fabric makes for a more comfortable garment and causes less seamstress. It also tends to increase the breaking strength of the fabric.
• Complete recovery helps prevent bagginess from occurring at elbows or knees, and it prevents the garment from becoming loose fitting.
• Fibers that can elongate at least 100 percent are called elastomeric fibers. Spandex, elasterell-p, lastol, and rubber are fibers in this category.
• After being stretched, these elastic fibers return forcibly to approximately their original dimensions.

Wicking

• Wicking is the ability of a fiber to transfer moisture from one section to another.
• Usually, the moisture is along the fiber surface, but it may also pass through the fiber when a liquid is absorbed by the fiber. The wicking propensity of fiber usually is based on the chemical and physical composition of the outer surface.
• A smooth surface reduces wicking action.
• Some fibers, such as cotton, are hydrophilic and also possess good wicking action. Others, such as olefin, are hydrophobic but possess good wicking action when micro denier in size (i.e. very thin filament fibers).
• This property is especially desirable in workout clothes and running clothes.

Safety

Flammability

• Flammability is the ability to ignite or burn. This characteristic is important because people’s lives are surrounded by various textile products.
• We know that the burning of apparel or interior furnishings can cause serious injury and/or result in a significant material loss for the consumer.
• Fibers are usually classified as being flammable, flame resistant, or flameproof:
  • Flammable fibers are relatively easy to ignite and sustain combustion.
  • Flame-resistant fibers have a relatively high ignition temperature and a slow rate of burning. They may also be self-extinguishing.
  • Flameproof fibers will not burn.
• Flammable fibers can be made flame-resistant through finishing.

Identification of Fibers

Three methods

1. 1. Microscopy
   2. Burning Test
   3. Solubility Tests

Microscopy

• Identification of natural fibres easy
• Identification of synthetic fibres difficult
• May indicate the presence of more than one type of fibres

Burning Tests

• Quick tests
• A simple method for identifying the fibres
• Knowledge of the burning properties of the fibres essential
• Aspects studied – the behavior of the material on approaching the flame, in the flame, on coming out of the flame, its odor, and residue

Solubility tests

• Fiber identification can be made when it is determined which chemical will dissolve the specimen.
• The specimen is stirred in the liquid and the results are noted.
• Extreme care should be taken because most of the liquids are hazardous. Gloves, aprons, goggles, and laboratory-exhaust hoods should be used during these tests.
• Used for qualitative and quantitative assessment of fibres and their blends.

Some basic fiber properties, pros, and cons that are applicable to the home sewing consumer include:

• Natural Cellulose Fibers: Cotton and Flax are examples of natural cellulose fibers. These have good absorbency and are a good conductor of heat. They wrinkle easily and pack tightly. They are heavy fibers, very flammable, and printed easily.
• Natural Protein Fibers (Wool): These fibers have an animal origin. They resist wrinkling. They are hygroscopic-comfortable in a cool, damp climate but weaker when wet because they shrink. Natural protein fibers are harmed by dry heat. They are flame resistant and dye well.
• Synthetic Fibers: These are fibers made from chemicals. They are heat sensitive and they melt easily. They are resistant to moths and fungi, have low absorbency, and are abrasion-resistant. Synthetic fibers are strong and easy to care for. They are less expensive and
  readily available.