Fiber properties

Definition

Fiber properties are essential thing to know for various end uses and the products made from it qualify on the basis of certain parameters.
The various properties are-
1. High fiber length to width ratio.
2. Tenacity (adequate strength).
3. Flexibility or pliability.
4. Cohesiveness or spinning pliability
5. Uniformity.

6. Fiber morphology
7. Specific gravity
8. Elongation and elastic recovery
9. Resiliency
10. Moisture regain
11. Flammability and other thermal reactions
12. Electrical conductivity
13. Abrasion resistance
14. Chemical reactivity and resistance
15. Sensitivity to environmental conditions.

High length to width ratio-
A pre-requisite for processing of fibers into yarns and fabrics is that their lengths must be more than widths. The minimum length to breadth ratio is 100:1.

Length of fibers is also a basis for classifying them into two groups staple and filament. Staple fibers are of relatively short length fibers; and filament fibers are long length fibers.

The fineness of a natural fiber is a major factor in ascertaining quality and is measured in microns(1 microns= 1/1000millimeter). In general, finer fibers are softer, more pliable and have better drapability. They are, thus, considered superior and form better yarns and fabrics. Fineness of man-made fibers is controlled by the size of spinneret holes.

Tenacity-

the strength of textile fibers is referred to as their tenacity. It is determined by measuring the force required to rupture or break the fiber. Sufficient tenacity is required to withstand the mechanical and chemical processing as well as make textile products which are durable.

Tenacity is, directly related to the length of the polymers, degree of polymerization, strength in dry and wet conditions, and types of inter-polymer forces of attraction formed between the polymers.
Its unit are -gram/denier(g/d) or gram/tex (g/t)

Flexibility-
Fibers should be flexible or pliable in order to be made into yarns and thereafter into fabrics that permit freedom of movement. Certain end uses require greater flexibility, e.g., automobile seat belts.
Uniformity-
Uniformity of fibers towards its length, ensure production of even yarns which can then form fabrics of uniform appearance and consistent performance.

Cohesiveness or spinning quality-
It is the ability of the fiber to stick together properly during yarn manufacturing processes.

Natural fibers have inherent irregularities in their longitudinal or cross sections which permit them to adhere to each other during fiber arranging.

In case of synthetics, filament lengths aid in yarn formation. Texturing introduces coils, crimps, curls or loops in the structure of an otherwise smooth filament. It is used to impart cohesiveness.

Morphology-
It is the study of physical shape and form of a fiber. It includes microscopic structure like longitudinal and cross sections. These also include fiber length, fineness, crimp, color and luster.

Physical shape-
shape of a fiber include, its longitudinal sections, cross section, surface contour, irregularities and average length.

Luster-
It refers to the sheen or gloss that a fiber possesses. It is directly proportional to the amount of light reflected by a fiber.
This in turn is affected by their cross section shape.

Among the natural fibers, silk or the queen of fibers has a high luster, and cotton has low.

Deluster-
A delusterant is a substance that is added to the dope before spinning of manufactured fibers.

Finally powdered metallic salts like titanium dioxide (TiO2) and geranium dioxide (GeO2) are used. These act as discontinuities in an otherwise regular, uniform reflection of light.

The amount of delusterant added could vary and thus result in semi-lustered or delustered fibers.

Specific gravity-
The specific gravity of a fiber is the density related to that of water(at 4°c).

The density of water at that temperature is 1. fiber density will affect their performance and laundering.

If the specific gravity of a fiber is less than 1, it will float in water, making its washing and dyeing very difficult. E.g. Olefins fiber.

A related property is density which is defined as the mass per unit volume and measured in g/cubic cm.

Elongation and elastic recovery-
The amount of extension or stretch that a fiber accepts is referred to as elongation. Elongation at break is the amount of stretch a fiber can take before it breaks.

Elastic recovery indicates the ability of fibers to return to their original length after being stretched. A fiber with 100% elastic recovery will come back to its original length after being stretched to a specific degree for specified period of time. After removing and re-measured.

Resiliency
Resiliency refers to the ability of a fiber to come back to its original position after being creased or folded. Resilient fibers recover quickly from wrinkling or creasing. Good elastic recovery usually indicates good resiliency. This property is described qualitatively and ranges from excellent to poor. Excellent resiliency is exhibited by polyester, wool and nylon fibers. Flax, rayon and cotton, on the other hand, have a low resiliency.

Moisture regain-
The ability of a bone dry fiber to absorb moisture is called moisture regain. Measurements are done under standard testing conditions (70°± 2F and 65% ±2% relative humidity). Saturation regain is the moisture regain of a material at 95-100% relative humidity. Both regain and content are expressed as a percentage.
Moisture regain= wt. of water in a material × 100
oven dry wt.
Moisture content= wt. of water in a material × 100
total wt.

Flammability and other thermal reactions-

Burning characteristics of fiber groups vary from each other and can, thus be used as an authentic identification method. Reaction to flame can be further broken down into; behavior when approaching flame, when in flame, after being removed from flame.

Thermal characteristics of fibers are important in their use and care like washing, drying and ironing are selected on the basis of a fiber’s ability to withstand heat.

Electrical conductivity-

It is the ability of a fiber to transfer or carry electrical charges. Poor or low conductivity results in building up of static charges. This leads to the clinging of clothing and in extreme cases can produce electrical shocks, which produce crackling sound or even a tiny spark. Acrylic is a poor conductor of electricity.

water is an excellent conductor of electricity and fibers with high moisture regains will never face the problem of static build-up.

Abrasion –
The wearing away of a material by rubbing against another surface is called abrasion. Different kinds of abrasion are identified, these are-

Flex abrasion- when a fabric bends/folds and rubs against another surface e.g. on elbow or knee areas.

Flat or plane abrasion: when a flat surface rubs against another surface e.g. on thigh area of a pair of jeans.

Edge abrasion- which occurs on the curved edges e.g. collars, cuffs and trouser hem.

Chemical reactivity and resistance-
Chemical reactivity plays a key role in manufacture, application of finishes and care of fabrics.

Resistance to acids, alkalis and organic solvents in similar for fibers of one chemical composition. Thus, cellulosic’s are fairly resistant to alkalis but get harmed by acids and the reverse is true for protein fiber.

 

 

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