Properties of Textile Fibers

Properties of Textile Fibers:
Textile fibers are perhaps most obviously characterized by their fineness; they are long and very thin. There are numerous fibrous structures in nature, but only those that can be converted into yarns are suitable for constructing textile fabrics.

Textile fibers are used for a wide range of applications, but in order for them to be useful, they must possess adequate properties in various categories. Typical categories that have to be considered in deciding if a fiber is suitable for a particular end use. Before learning about properties of fiber, you should know about what is textile fiber? We can define fiber as; any substance, natural or manufactured, with a high length to width ratio and with suitable characteristics for being processed into fabric; the smallest component, hair like in nature that can be separated from a fabric. I have also published a complete post on textile fiber.

Textile materials are capable of being transformed into desired shapes without resistance and durable over a reasonable period of wear. They derive these properties from fibers and yarns. The yarn, in turn, is formed by twisting a bundle of fibers together. It is therefore clear that the properties of the ultimate textile structure will depend very largely on the characteristics of the fibers from which they are made. These dimensional characteristics of fibers form the basis of their use as textile raw materials.

To be a textile fiber it has some properties. The properties of textile fibers are discussed below:

Classification of Fiber Properties:
To be designated as a textile fiber any material should satisfy two important properties, namely:

Essential or Primary properties of textile fibers
Desirable or Secondary properties of textile fibers

A. Essential or Primary properties of textile fibers:

High length to width ratio
Tenacity
Flexibility
Spinning quality (Cohesiveness)
Uniformity

B. Desirable or Secondary properties of textile fibers:

Physical shape
Elastic recovery and elongation
Resiliency
Flammability and other thermal reactions
Density
Luster
Color
Moisture regain

In broadly, properties of textile fibers are classified in below ways:

Physical Properties
Chemical Properties
Mechanical Properties

1. Physical properties:

Length ——— Staple (15mm – 150 mm)
Tenacity / Specific Strength (g/den)
Fineness ———Length : Width = 1000:1
Crimp
Cross Sectional Shape
Maturity
Luster
Softness
Resiliency
Work of rupture
Density
Appearance
Flexibility
Toughness
Elongation
Moisture Regain (MR%) and Moisture Content (MC%)
Specific Gravity (g/cc)
Elastic Recovery (%)
Initial Young Modulus (g/den)
Breaking Length (km)
Extension (%)
Swelling
Static Electrification
Discoloration
Specific Heat
Burning Behavior
Thermal Conductivity
Pilling Behavior
Limited Oxygen Demand (LOI %)
Degradation

2. Mechanical properties:

Strength (Tenacity) (P.S.I)
Elasticity (Recovery percentage)
Extensibility (Breaking Extension)
Rigidity (Stiffness)

3. Chemical properties:
Solubility in aqueous and organic solvent. Useful properties of another hind desired in a textile fiber are indicated bellow.

Behavior towards dyes.
Ability to moisture absorption
Resistance to deteriorating influence including; light, thermal stability, resistance to bacteria, mildow moth and other destructive insect, corrosive chemicals.

Without above those properties, textile fiber has also below properties:

Electrical Properties: Electrostatic build‐up
Thermal Properties: Melt temperature, Tg, thermal decomposition, flammability
Biological Properties: Resistance to microorganisms, biocompatibility, biodegradation
Optical Properties: Reflection, refraction, luster, transparency
Surface Properties: Wetting, friction
Structural Properties
Acoustic Properties
Radiological Properties
Environmental Properties
Torsional Properties
Frictional Properties

A brief idea of some of the properties of textile fibers is as under-

a) Fiber length:
It is one of the most important properties. Other factors being equal, the longer the fiber, the stronger the yarn. The lower limit of length in case of commercial textile fibers should not be less than 1 cm. A fiber having a length below the commercial limit, cannot be spun economically.

Most natural textile fibers exist as staple fibers and their length varies considerably. For example, the lengths of cotton fibers range from 12 to 36 mm (depending on the quality), whilst those of wool fibers range from 50 to 400 mm. Fibers whose lengths are less than 10 mm are not suitable because they are too short to be spun into yarn.

The characteristics of yarns depend on the staple fiber length. A fluffy, spongy yarn with a soft handle is obtained from shorter fibers, where many loose ends remain disoriented in the yarn. Fibers with longer staple lengths give smoother, finer yarns with a higher luster and higher strength.

Synthetic fibers are produced in the form of continuous filaments, which are long, continuous strands of fiber. They can be used in this form but it is usual for them to be cut into predetermined lengths (i.e. staple fibers) to suit the type of yarn needed. Natural and synthetic fibers are often blended together when making yarns (e.g. wool/nylon, cotton/polyester), giving the benefits of both fiber types. For this purpose the length of the synthetic filament may be cut to match that of the natural fiber, thus making it possible to use the same spinning machinery for both fibers. The only natural fiber that is obtained as a continuous filament is silk, produced from silk worms.

b) Fineness:
In a fiber, the ratio of length to width or cross-sectional area is expressed as its fineness. In coarse fibers the length is about 700 times more than the width. The ratio may be even 5000 in case of very fine fibers. Only fine fibers can produce fine yarn. Fineness has much role to determine properties and characteristics of particular fiber. It also determines the end use of fibers to some extent.

The fineness of fibers also has an important bearing on the properties of yarns and fabrics made from them. There are various ways of representing fineness (the count). It can be expressed as the diameter in microns, where 1 micron, μm = 0.001 mm. Fine fibers have diameters lesser than 18 μm, medium fibers between 18 and 25 μm and coarse fibers greater than 25 μm. In general, the finer the fibers, the better their quality, because they feel softer and are more comfortable next to the skin. Fibers with a diameter of more than 40 μm tend to scratch and stick to the skin because they do not deflect easily.

c) Crimp:
Crimp is the waviness of a fiber. It is natural quality of wool. It is measured by the difference between the length of the crimped fiber at rest and the length of the same fiber when it is perfectly straight. It is expressed as percentage of the unstretched fiber length. Finewools usually have many fine waves. Coarse wool is more, definitely curled rather than crimped.

d) Density:
Density is the mass or weight of material per unit volume generally expressed in grams per cubic centimetre (gmj cc). The specific gravity or specific weight is the ratio of mass weighed in air to the mass of an equal volume of water at 4°C.

Since the volume is affected by the lumen in hollow fiber, the porosity (resulting from surface cracks) and the amount of crystallanity in certain sections of the individual fiber it is very difficult to determine the true density. In this case specific gravity is generally the preferred method of expressing the weight of the textile fiber.

e) Strength:
Strength is also one of the most important characteristics of a textile fiber. Strength of any material is derived from the load it supports at break and is thus a measure of its limiting load bearing capacity. Weak fibers cannot produce a strong yarn. Individual fibers must have sufficient strength to withstand normal mechanical strain in the processing. The resistance of a fiber to use and wear is considerably dependent on its tensile strength.

Tensile strength of textile fibre is measured as the maximum tensile stress in force per unit cross-sectional area or per unit linear density, at the time of rupture called ‘tenacity’, expressed in terms of grams per denier or grams per tex units. In Standard International Unit (SI Unit) tenacity is expressed as millinewtons per tex mN/tex (mN/tex = gf/den × 88.3, mN = gf × 9.8).

f) Elasticity and elongation:
To be used as textile material, a fiber must have some elasticity. It is the property by which the fiber tends to recover its original length upon the removal of stress that caused deformation. The elastic limit is the maximum load or stress to which a fiber can be subjected without the formation of a permanent set when the load is removed. The amount of stretch or extension that a fiber will accept is referred to as elongation. Breaking elongation is the amount of stretch that a fiber can undergo before it breaks.

g) Spinnability:
Spinnability includes several physical properties each having an effect on the ability of the fibers to be spun into yarn. Staple fibers must have to be capable of taking a twist. They must have a certain degree of friction against one another to stay in place when pull is applied to the yarn. They must also be able to take on whole special finishes for lubrication during spinning or to provide additional surface resistance to abrasion.

h) Uniformity:
Uniformity means the evenness of the individual fibers in length and diameter. A fiber possessing this property can produce reasonably even threads. This is also important in connection with the strength of the resulting yarn. The more uniform the yarn the stronger the yarn.

i) Plasticity:
It is the property of a solid by which under certain conditions of temperature and pressure it can be made to take on the shape of any mould and to retain this shape after cooling. The synthetic fibers being thermoplastic materials possesses this property. They are all heat softened.

j) Absorbency:
Most of textile fibers absorb moisture from it is important that the market purchaser of fibers and yarns should know their moisture content so that they will not be paying fiber prices for water.

The amount of moisture present is expressed as a percentage of the original weight (Moisture content) of fibers or its oven dry weight (Moisture regain). The fiber that absorbs moisture are more comfortable than those with low absorbancy especially in hot humid weather when perspiration is removed.

k) Cohesiveness:
Cohesion is the property of clinging or sticking together in a mass. It is the property of an individual fiber by virtue of which the fibers hold on to one another when the fibers are spun into yarn. Usually the more rigid the fiber lower its cohesion. It is generally assumed that a high degree of frictional resistance plays a part in the cohesiveness. It is certain that external scales, neps (the surface irregularities on wool and flax respectively), twist and irregularitiness in the diameter of cotton contributes to the ability of such fibers to hold together.

l) Resilience:
Resilience is the springing back of recovery of a fiber when it is released from a deformation. The resistance to compression, flexing or torsion varies from fiber to fiber. Resiliency is also a desirable property of fiber fillings for pillows and mattresses and some types of wearing apparel.

m) Static electrical resistance:
Phenomenon of Static Electricity creates a problem in the spinning and other processing of textile fibers. The problem is more especially in a room with very low relative humidity. It is much more severe in the case of synthetic fibers which have extremely low electrical conductivity and too little moisture to provide a path where by the static electricity can be carried away. Static electrical properties create problems in the packaging and sewing also.

n) Capillarity and porosity:
These properties with the similar influence on the ability of a textile fiber or yam to accept and hold a dye, a finish, a lubricant or resin finish in order to increase the wrinkle resistance of a fabric and to give a wash and wear finish. Liquids passed rapidly through small cracks or breaks in the outer surface of a fiber bringing about absorption through porosity. In the case of cotton liquids pass through the hollow center or lumen and in wool through small voids on the surface. It is usually regarded as the effect of the mechanism, capillarity.

o) Durability:
A textile fiber should withstand processing treatments and should not be easily susceptible to physical, chemical and bacteriological attack, which may result in damage and decomposition.

The durability of clothing to average wear and tear depends somewhat more on the elasticity, flexibility and resistance of the fiber and fabric, rather than the absolute strength of either fiber or fabric. If a fabric possesses these three properties, its garment will absorb or counter more readily stresses and strains during wear. It will allow itself to be deformed with less resistance, thus reducing the chance of intermediate tearing or twisting. For these reasons wool garments owe much of their durability to the elasticity, resilience and flexibility of the fiber and fabric, even though wool is a weak fiber.

Strength combined with these properties provides excellent durability that is why nylon and polyester fiber fabrics seem to last forever. Strength and reasonable flexibility can also provide good durability as illustrated by cotton which lack elasticity and resilience.

p) Color:
Most natural fiber have some color e.g. silk is yellow to tan. Wool is brownish tint. Cotton is a creamy white or brown. This is a natural coloring matter and requires to be removed before subsequent wet processing treatments such as dyeing and printing.

The removal is done with bleaching agents. Most of the synthetic fibers too have a slight creamy or yellowish color. Therefore, they must be bleached or boiled and stripped off their color by some chemical process in order to produce a fiber or yarn as white as possible.

q) Commercial availability:
All the essential and desirable properties of a fiber put together will be of much use only if the fiber is available in large quantities at fair price, when it is needed. The accurate estimate of the different type of fibers available for the consumption and the source of availability makes the supply of commercial fibers to establish itself with reasonable assurance of exactness.

Following are the properties desired for basic textile fibers:

A. In Apparel and Domestic Application:

Tenacity: 3–7 grams per denier (gpd)
Elongation @ break: 10–35%
Recovery from elongation : 100% at strain up to 5%
Modulus of elasticity : 30–60 gpd
Moisture absorbency: 2–5%
Zero strength temperature: Excessive creep and softening point >215°C
High abrasion resistance
Dyeable
Low flammability
Insoluble (low swelling) in water, in moderately strong acids and bases and conventional organic solvents from room temperature to 100°C
Easy care

B. In Industrial Applications:

Tenacity: 7–8 gpd
Elongation break: 8–15%
Modulus of elasticity: 80 gpd or more, wet: 50 gpd
Zero strength temperature: Excessive creep and softening point >250°C

C. Polymer Composition and Structure:

Melting point
Modulus
Elasticity and recovery from strain
Tensile strength
Density
Moisture absorption
Dyeability
Comfort
Abrasion resistance 1.3

References:

Physical Properties of Textile Fibers (Fourth edition) by W. E. Morton and J. W. S. Hearle
Introduction to Textile Fibers By H. V. Sreenivasa Murthy
An Introduction to Textile Coloration: Principles and Practice By Roger H. Wardman
Textile Raw Materials By Ajay Jindal and Rakesh Jindal
The Chemistry of Textile Fibers by R. H. Wardman and R. R. Mather

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Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.