Essential and Desirable Properties of Textile Fibres

What is Textile Fibre?
Generally textile fibre is a raw materials for textile finished products. If we define textile fibre then we can say, a textile fibre is a fine single filament which is used in making of yarns and thread which comprise of the basic component of all textile items- such as fabrics, mats, strings, cords, twines and ropes. It is defined as a fine strand of tissue of plant, animal or any synthetic material drawn out into filament and subsequently cut into required length. Many fibrous materials are not suitable to make into fabrics, e.g., corn silk or wood slivers. Textile fibers must have certain properties. So we can say that all fibers are not textile fibres.

properties of textile fibres

Technologists have defined the term Textile fibres as those fibres which can be spun into a yarn or made into a fabric by interlacing, or interlooping in a variety of machines including weaving, knitting, braiding, felting, bonding, etc.

Properties / Characteristics of a Good Textile Fibre:
Textile fibres are perhaps most obviously characterised 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. To be designated as a textile fiber any material should satisfy two important characteristics, namely, the essential or the primary properties and the desirable or the secondary properties.

Essential / Primary Properties of Textile Fibres:

  1. Fibre Length
  2. Fibre Strength and related properties
  3. Fibre Flexibility
  4. Fibre Cohesiveness

Desirable / Secondary Properties of Textile Fibres:

  1. Fineness
  2. Resiliency
  3. Colour
  4. Uniformity
  5. Porosity
  6. Lustre
  7. Durability
  8. Commercial availability
  9. Trash Content

Essential / Primary properties of textile fibres:
Fibre length, strength, cohesiveness and flexibility are the four essential textile fibres properties.

1. Fibre Length: This is the most important property, along with its strength. Most natural textile fibres exist as staple fibres and their length varies considerably. For example, the lengths of cotton fibres range from 12 to 36 mm (depending on the quality), whilst those of wool fibres range from 50 to 400 mm. If a fibre is to be spun into yarn, there needs to be a minimum fibre length of 5 mm. It is because with the traditional spinning methods, it is not possible to spin the yarn below this length. The length alone does not suffice the purpose. In addition, its relation to fibre thickness is equally important. The length to diameter (thickness) ratio needs to be at least a hundred times. Many a time, another indicator called “uniformity ratio” is also used. It is the ratio of the mean length of the fibre (50% span length) to its upper half mean length (2.5% span length), expressed as percentage.

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

2. Fibre Strength: Strength of any material is derived from the load it supports at break and is thus a measure of its limiting load bearing capacity. Normally strength of a textile fibre is measured in tension when the fibre is loaded along its long axis and is designated as Tensile strength.

Mechanical properties have an important bearing on the end uses to which fibres can be put. Strength gives the fibre the ability to withstand the stress-strain caused during its conversion to yarn and fabrics. Certain fibres such as Kapok not only have very short length but also lack adequate strength. The strength is measured as force per unit cross-section when fiber breaks and is expressed as g/d, g/tex or cN/tex. When the two different fibres are to be blended, it is very important to select the components so that they have matching stress-strain curves. When the yarns are spun with this criterion, the two component fibres share the load almost equally.

3. Fibre Flexibility: One of the most important operations in yarn forming is twisting. It binds the fibres together to form a yarn having worthwhile strength. During twisting operations, the fibres are strained. The ability of the fibre to try to spring back is flexibility. It makes the fibre pliable.

4. Fibre Cohesiveness: The fibres as a bundle finally make the yarn. The ability of the fibres to form the yarn depends upon their cohesive action to hold on to each other. In fact, it is the surface characteristics which give the frictional property to the fibres with which they are able to hold on to the other fibres. The cohesiveness appears in a different form. In cotton, it is due to natural convolutions during their growth. The crimp in the woollen fibres gives them this ability. In man-made fibres, however, this needs to be specially imparted. Viscose is manufactured with serrated cross-section, while polyester fibre is crimped. This is because uncrimped synthetic fibres, as it is, are quite smooth and rod-like structures. In this form, it is very difficult to make them hold together even when twisted.

Desirable / Secondary properties of textile fibres:
Apart from these essential properties, a fibre becomes more useful if it also has some desirable properties. Therefore, even when a yarn can be made with a fibre only having essential properties, a still better yarn can be made when it also possesses some of the following desirable properties.

1. Fineness: The fineness of fibres 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 is a measure of both the diametric size and linear density of the fibres. In the case of artificially manufactured fibres, the diameter of the fibre is proportional to linear density, except in the case of “hollow” fibres. With natural fibres, the fibre maturity governs the linear density, hence it is customary to define the fibre fineness in terms of weight per unit length with such fibres. The following are some of the units of measure: Micron: 10‒4 cm, especially used in the case of wool fibres to specify diameter. Micronaire: It is another measure of judging both the fineness and maturity of the fibres. Micro-grammes per inch: 10‒6 grammes per inch for expressing linear density. Tex or Denier – grammes per 1000 m or 9000 m, respectively. This unit is specially used for fibres and filaments There is a lot of variation in diameter (20–30% for wool or silk) in the case of natural fibres, whereas man-made fibres can be manufactured more precisely (3–5% variation only).

2. Resiliency: Fibres exhibit a beautiful property called resiliency. This is disclosed when a fibre is stressed. Here, they try to yield; and when the stress is removed, they try to spring back, i.e. recover their shape and size. Fibres like wool show excellent resilience. During the twisting operation, this property of resiliency becomes very useful when fibres try to regain their original state. Under this condition, a constant pressure is experienced by the inner mass of the fibres, and it helps in holding the inner mass and the peripheral fibres together.

3. Colour: The colour of the cotton is judged by two parameters – Degree of Reflectance (Rd) and Yellowness (+b). While degree of reflectance shows the brightness, yellowness depicts the degree of cotton pigmentation. The colour gets affected by atmospheric conditions, impact of insects, fungi, type of soil and storage conditions. There are five recognized groups – White, Gray, Spotted, Tinged and Yellow-stained.

4. Uniformity: The artificial fibres can be very precisely manufactured as for their weight per unit length and length itself. But, it is not so with natural fibres. Therefore, in spite of the same growing conditions, natural fibres greatly vary in their size and length. Silk, when formed during cocoon formation, greatly varies in its size. Fibres like cotton have large variation, both in terms of linear density and length. Flax fiber and jute fibres are much stronger natural fibres, but the fibre dimensions greatly vary, thus producing uneven yarn and fabric.

5. Porosity: The property of absorbing moisture or any liquid within the fibre arises owing to its porous nature. With the natural fibres, the amorphous and crystalline regions vary in their dimensions. It is the amorphous regions that give the fibre property of absorption. With man-made fibres, the drawing operation improves the crystalline regions, thus imparting strength. However, their absorption capacity is much limited.

6. Lustre: Among the natural fibre, silk is probably the one having maximum lustre. Egyptian cotton has natural silky lustre. Lustre as such is not essential, but when a fibre possesses pleasing lustre, it adds to the appearance. The process of mercerization helps in imparting round shape to the cotton yarns and in improving its lustre. Almost all man made fibers show far better lustre than many of the natural fibres. However, the glittering reflection of light is not very pleasant. In fact, for this, in some cases, the fibre-dulling process is followed during the manufacture of some man-made fibres.

7. Durability: As mentioned earlier, during the conversion of fibre to finished fabric, the fibre, the yarn and subsequently the fabric have to undergo pro-cessing, which puts a lot of strain on them. The fibres and their subsequent forms, therefore, should possess durability to sustain these stresses. Even the normal washing/laundering processes or exposure to light and heat require some resistance. The adverse effects of chemicals like alkalis/acids/bleaching agents and bacterial attacks have to be fought against. Fibre durability counts in all such cases.

8. Commercial Availability: The supply of regular raw material in the form of fibres is another important criterion. When a particular variety of raw material is not available in plenty, the fibre-processors are forced to switch over to another variety to continue manufacture of the same variety of the goods. The commercial availability is thus another desirable characteristic.

9. Trash Content: It is the non-lint material in the bale cotton and is required to be removed before spinning the yarn. Similarly, in all other natural fibres, there is useless and unwanted content. The higher trash content in cotton or in other natural fibres is, therefore, always a problem. Especially in better grade cottons, the high trash content is a huge problem. The trash content in cotton is highly related to leafy vegetable matter, dirt and dust. Normally, the trash content in the different types of cotton varies greatly from 1% to 6–8%.

References:

  1. Principles of Spinning: Fibres and Blow Room Cotton Processing in Spinning By Ashok R. Khare
  2. An Introduction to Textile Coloration: Principles and Practice By Roger H. Wardman
  3. Introduction to Textile Fibres by V. Sreenivasa Murthy
  4. Textile Raw Materials By Ajay Jindal and Rakesh Jindal
  5. The Chemistry of Textile Fibres by R. H. Wardman and R. R. Mather
  6. Physical Properties of Textile Fibres (Fourth edition) by W. E. Morton and J. W. S. Hearle

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