What are Fibres, their classification and extraction.

Basics of Fibres and their Classification

Definition of Fibres: Fibers are thread like or slender in structure, fine or coarse, flexible or stiff, elastic or soft, differ in their structure and chemical composition, and also in the part from which they are derived.

Fibres are separately weak but form strong when twisted, woven, or joined together.

Cellulosic fibers originated from plants and trees such as cotton, flax, hemp, jute, ramie, kapok, coir and bamboo are termed natural Plant Fibers. 

 

CLASSIFICATION OF FIBRES 

Fibers may be classified most conveniently into the following groups: 

(1) surface fibers:  more or less hair-like outgrowths. 

Occur upon stems, leaves, fruit, and seeds. 

The only one of much economic importance is cotton.

The fibers found on the seeds of each consist of simple, flattened and twisted hairs developed as outgrowths from the “hull” or seed coat

(2) bast fibers: consisting entirely of such tough strands as form the bast or strength-giving part of the inner bark of stems.

The bast fibers are mainly extracted from Phloem, pericycle and cortex.

Strongest and most elastic part of the framework of plants.

These fibers consist of nearly solid cylinders of almost pure cellulose.

Jute, hemp and Flax are the examples of Bast fibers.

The bast is extracted from the stem of jute. The bast of a plant forms the main strengthening element of its stem.

(3) woody fibers, composed entirely of wood.

(4) mixed fibers, containing both woody and bast-like fibers.

(5) pseudo-fibers, which consist either of entire plants or of parts lacking both wood and bast.

HOW FIBERS EXTRACTED FRM PLANTS ?

The process that separates the fibers into smaller bundles and elementary fibers is known as RETTING.

Retting is the process by which pectin gets dissolved or softened from the fiber bundles and separates the fibers from stems through microbial activity. 

As such, a group of Clostridium microorganism is commonly known to play a significant role in the process by hydrolysing the pectin as it produces pectinase enzyme. 

These enzymes initially attack the cambium layer and then the other thin-walled cells in the cortex. 

This phenomenon takes place in most plant bast fibers as they have similar long filament structures, except those from cotton fibers which are single plant cells.