Physical properties of textile fibers?

Fiber length

In physical properties the most important is the fiber length on which the quality of yarns depends. For cotton if fiber length increases the quality of yarns will be good, but this is just opposite for wool. In jute the fiber length is too long that sometimes the fibers are cut into small pieces.

If the fiber length is too small it is difficult to produce yarn. Yarn is impossible if the fiber length is less than 0.5 inch. Thin fibers produce thin yarn and coarse yarn is produced from coarse fibers.

There are two types of fiber on the basis of length:

1. Continuous filament

2. Staple fiber

Continuous filament

Long and continuous fibers are called filament. Filaments are continuous in length which can be used as such form or cut into shorter staple fiber form. These fibers are collected from both natural and artificial source. Any natural fiber can be made into a filament. When only one filament is used in a yarn then it is called mono filament. When more than one filament are used in yarn then it is called multi filament.

Mono filament → 1.5 holes in spinneret.

Multi filament → 10-100 holes.

Staple fiber

When the length of fiber is short then it is called staple fiber. Stable fibers are manly shorter in length and related to natural fiber. All natural fibers without silk can be collected as staple fiber. Artificial fibers also collected as staple fiber.

Staple fibers are three types on the basis of length:

 

    Short staple: Length is less than 2 inch.

    Medium staple: Length is from 2-4 inch.

    Long staple: Length is more than 4 inch.

Strength

The capacity of a fiber to support a load is known as fiber strength. The strength is described as tenacity.

Tenacity = Strength/ linear density.

It is expressed as CN/Tex or N/Tex. The tensile strength is commonly described as the force required to reach break the increase in the length before breaking is known as extension.

Elasticity

It is the property to recover from deformation. The fiber may be elastic or plastic which depends upon fiber condition and surrounding environment.

Flexibility

Flexibility is that property to resist repeated bending and folding.

Cohesiveness

It is the ability of the fibers to cling together during spinning depends on crimp and twist. In natural fiber the property comes from nature but in artificial fiber this property is given by crimping.

Fineness

The term fineness describes the quality of a fiber. By this, we know how fine a fiber is. It is expressed by the terms count, tex, denier, tex per unit length etc.

1 Tex = 1 gm/1000m.

1 denier = wt. in gm/900m.

Fineness affects some fiber properties. Such as yarn count, yarn strength, yarn regularity etc.

Cross section

The cross section of a fiber determines the physical properties of fiber. It gives idea about strength, fineness that varies from fiber to fiber. The cross section shape of a fiber is important because it contributes to the surface appearance of the fiber. It helps to give properties of luster, bulk and body of the fibers, yarn and fabrics. It has effect in twisting, bending or shunning.

Crimp

It refers to the waves or bends that take place along the length of a fiber. It increases cohesiveness and resilience, resistance to abortion and gives increased bulk or warmth to fabrics. It also helps fabrics to maintain their softness or thickness, increase absorbency and show contact comforts bid reduces luster. A fiber may have one of the three types of crimp. Namely – Mechanical crimp, natural crimp or Inherent crimp and Chemical crimp.

Resiliency

It is the property of a fiber, which enables it to recover from certain load or stretch over a period of time.

Toughness

The ability of a fiber to endure large permanent deformations without rupture is called toughness.

Work of rupture

The area below the stress –strain curves provides a measure of the work required to break the fiber. It is called work of rupture and it commonly expressed in CN/Tex.

Appearance

It is expressed by length, fineness, cross-section cleanness and luster of a fabric. Generally short fibers are bulky and loss lustrous.

Density

The density indicates the mass per unit volume. The specific gravity of a fiber indicates the density relative to that of water at 4 degree Celsius.

Elongation

It is the ability to be stretched, extended or lengthened. Elongation vary at different temperatures and when wet or dry.

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Thermal properties of textile fibers?

Amorphousness

Amorphousness orientation of polymers within the polymer system of any fiber is called the amorphous region. In other word, if a substance exposed to X-rays and diffuse and broad patterns X-ray diffraction called amorphous substance and the property is called amorphousness. In amorphous regions, the polymers are oriented or aligned at random.

 Crystallinity

If a substance is exposed to X-rays, give sharp and well defined X-ray diffraction patterns is called crystalline substance and the property is called Crystallinity. Crystalline orientation of polymers within the polymer system of any fiber is called the crystalline region. In crystalline regions the polymers are oriented or aligned longitudinally into more or less parallel order. It is in the crystalline areas that hydrogen bonding and Vander-Walls forces occur.

Flammability

It is the ability to ignite and burn.

Dye ability

It is the ability of fibers to be dyed.

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Mechanical properties of Textile fibers?

A.  Tensile properties

Tensile properties indicate how a material will react to the forces being applied in Tension. Some tensile properties are given below -

Tenacity

Tenacity is the maximum strength to break a fiber.

Breaking extension

It is expressed in percentage. It is the ratio of elongation at break to the initial length and multiple of hundred.

Work of rupture

The total energy needed or work done to break a fiber.

Initial modulus

Initial modulus is the stress needed to double the length of a fiber.

Yield stress

Yield stress is the stress for which the fiber or material starts yielding.

Work factor

It is the ratio of work of rupture to the product of breaking load and breaking extension.

Elastic recovery

The tendency of a fiber to recover its original size and shape. It is the ratio of elastic extension to total extension.

 

B.  Flexural properties

It is the property or behavior shown by the fiber or material when we bend it. The importance of Flexural properties is required when we wear cloth.

 

C.  Torsional properties

It is the property of fiber or material when a Torsional force is applied on it. Here Torsional force is a twisting force that is applied on the two ends of the material in two opposite direction.

 

D.  Frictional properties

Frictional properties are due to the friction between the fibers. These properties are shown during processing. Too high friction and too low friction is not good for yarn. Therefore it is an important property when yarn manufacturing and processing. 

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Chemical properties of textile fibers?

Acid and Alkali

Acid or alkali is harmful for cellulose and protein fibers. Therefore, the effect of acid and alkali must be known during bleaching, dyeing and finishing. Different fibers react differently with acid and alkali. For example, Cotton and Linen damaged when they are subjected to conc. Hydrochloric, Sulphuric and Nitric acids. Also dilute solution of those acids can make harm to the fibers. On the other hand, conc. alkaline solution is not harmful to Cotton and Linen. Wool is not affected by dilute solution of acid. But conc. acid and alkali damage wool easily. So acid or alkali must be chosen properly to use in different purpose and processing.

Water

Water is very important to determine the properties of fibers. According to the behaviors of fibers with water, fibers are classified into two groups – hydrophobic and hydrophilic. Water is used in process like scouring, dyeing etc.

Moisture Regain

Moisture regain is expressed as percentage. It is the ratio of oven dry weight of a material to the weight of water in this material and multiple of hundred.

Moisture Content

Moisture content is also expressed as percentage. It the ratio of oven dry weight of a material to the total weight (oven dry weight + weight of water in this material) of the material.

Absorbency

Normally, textile fibers absorb moisture. The ability of fiber to take up the moisture is known as absorbency. The absorbency is expressed in the terms of moisture regain. Among the all fibers cotton absorbs easily. For the property cotton requires more time to dry. Moisture regain of wool is 16%. It is 10% for silk. But it seems like dry after regain for silk. The cloths we wear are more comfortable which ability is higher to absorb.

Heat

Effect of heat si a vital point during dyeing, ironing, steaming and some other operations. Different fibers behave differently under heat. Some fibers burn where some scorch when heat is applied. Some fibers are not combustible e.g. mineral fiber, glass fiber etc. Cotton is easily flammable, wool is hardly flammable fiber.

Sunlight

When we wear cloth or fabric it comes into the touch of sunlight. It is very familiar to us. Effect of sunlight should be kept in mind for general people. Sunlight reduces the strength of cotton and it becomes yellow. Linen is better than cotton in sunlight. But cotton is better than silk.

Biological agent

If the fibers are attacked by bacteria’s, black spots are seen on the fibers as a result of which the strength of fiber is reduced. Its importance whether fibers attached by micro-organisms or not upon which strength of products depends. Cotton, Linen and rayon attacked by fungus. Silk, wool, acetate, tri-acetate and spandex have better resistance to mildew and other insects.

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What is Mercerized Cotton?

Mercerized cotton is a special kind of cotton yarn that is more lustrous than conventional cotton. It is also stronger, takes dye a little more readily, makes the yarn more resistant to mildew and reduces lint. It also may not shrink or lose its shape as much as "regular" cotton.

Mercerisation is a treatment for cellulose material, typically cotton threads, that strengthens them and gives them a lustrous appearance. The process is less frequently used for linen and hemp threads.

Mercerization, the process by which mercerized yarn is made, is named for the British chemist John Mercer, who developed the process and received a patent for his work in 1851.

Mercer found that adding caustic soda (lye) or sulfuric acid to cotton made the fiber swell and straighten. No one was too impressed by that, but in 1890 Horace Lowe developed a process by which caustic soda was added to the yarn under high tension, which added the luster that mercerized cotton is famous for today.

Thread :

The modern production method for mercerized cotton, also known as "pearl" or "pearle" cotton, gives cotton thread (or cotton-covered thread with a polyester core) a sodium hydroxide bath that is then neutralized with an acid bath. This treatment increases luster, strength, affinity to dye, and resistance to mildew. On the other hand, it also increases its affinity to lint.

Cotton with long staple fiber lengths responds best to mercerisation. Mercerized thread is commonly used to produce fine crochet.

Spool of a two-ply mercerized cotton thread with a polyester core. Individual staples can be seen in close up view.

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