Fibers
CLASSIFICATION:
- Vegetable origin – cotton, jute
- Animal origin – wool, silk
- Mineral origin – asbestos, glass wool
- Synthetic origin – nylon, terylene
- Regenerated from cellulose – rayon
- Regenerated from protein – milk protein, groundnut
COTTON / RAW COTTON:
BIOLOGICAL SOURCE:
- Trichomes of seeds of cultivated species of Gossypium herbaceum
- Family: Malvaceae
Collection:
- The capsule of cotton consists contains large number of seeds covered with trichomes
- The trichomes are separated
- Long trichomes are used in preparation of fabric & short ones are used in preparation of surgical dressings
- This non-absorbent cotton, when treated with dilute soda solution for 10 to 15 hours at a higher pressure, gets free of fats.
- The resulting absorbent cotton is dried, sterilized with gamma radiation
Description:
- White, soft to touch
Chemical Tests:
ABSORBENT COTTON:
- Fibre when treated with N/50 iodine solution & 80% H2SO4 gives a blue stain
- Fibre when treated with Cuoxam reagent, swells & dissolves
- Fibre gives a blue stain with chlorzinc iodide.
NON ABSORBENT COTTON:
- Fibre when treated with Cuoxam reagent, swells & dissolves with ballooning
- Fibre gives a violet stain with chlorzinc iodide
Uses:
- Fabrics, surgical dressings.
JUTE
- BIOLOGICAL SOURCE: obtained from phloem fibres of Corchorus capsularis
- Family: Tiliaceae.
Description:
- Brown, rough to touch.
Chemical Test:
- Fibre, when stained with phloroglucinol & HCl, gives a deep red colour
- Fibre gives a yellow stain with chlorzinc iodide
Uses:
- Preparation of jute bags.
SILK:
- BIOLOGICAL SOURCE: obtained from secretion/cocoon of Bombyx mori
- Family: Bombycidae.
Description:
- Yellow, smooth to touch.
Uses:
- Sutures & ligatures.
Collection:
- The larvae produce fibroin from the mouth glands which gets united with a gum-like secretion known as sericin to form a cocoon.
- These cocoons are exposed to steam & finally plunged in boiling water to separate the gum & the fibres.
Chemical:
- Proteins & subunits made of alanine & glycine.
Chemical Tests:
- Fibre does not blacken on treatment with lead acetate
- On treatment with Millon's reagent, it gives a brick red colour
WOOL
- BIOLOGICAL SOURCE: obtained from fleece of sheep Ovis aries
- Family: Bovidae
Description:
- Soft, lustrous.
Preparation:
- Raw wool is washed with water followed by a second washing with soap solution & then treated with sulphuric acid.
- The wool fat is separated by extracting with acetone.
- Thus wool fibre is obtained.
Chemical Test:
- Fibre blackens with lead acetate. (Contains sulphur containing amino acids)
Uses:
- Fabrication, ligatures & sutures.
GLASS WOOL:
- Source: made up of silica, mixture of silica & oxides of aluminium, calcium, boron & magnesium
Uses:
- Insulating material & in the manufacture of filters.
Chemical Tests:
- Fibre is partly soluble in 60% sulphuric acid
- Fibre on ignition forms a hard bead
ASBESTOS:
- Source: consists of hydrated magnesium silicates & occurs as white, yellow or green fibres.
Uses:
- Filtering media
Chemical Test:
- Fibre insoluble in warm HCl
NYLON
- Source: Polymer of adipic acid & hexamethylene diamine.
Description:
- It is dull or lustrous, white in colour.
Uses:
- Preparation of sutures & ligatures, sieves & fabrics.
Chemical Tests:
- Fibre soluble in warm HCl
- Forms a hard bead on ignition
TERYLENE:
- Source: Polymer of ethylene glycol & terephthalic acid.
Uses:
- Preparation of artificial grafts.
Chemical Tests:
- Fibre is soluble in formic acid
- Forms a hard round bead on ignition
RAYON / VISCOUS RAYON / REGENERATED CELLULOSE:
Preparation:
- Cellulose is treated with sodium hydroxide to yield sodium cellulosate.
- This, when treated with carbon disulphide in sodium hydroxide, gives sodium cellulose xanthate.
- The solution is passed through fine nozzles in a bath of sodium sulphate & H2SO4 to yield filaments of viscous rayon.
- It is further made free of sulphur, bleached & washed.
Uses:
- Preparation of surgical dressings & fabric.
SHORT NOTE ON CELLULOSE:
- Cellulose is obtained from wood or cotton
- It is extracted using hot methanol followed by methanolic NaOH treatment
- The solution is further exposed to an explosion process wherein the high pressure is cut down in a very short interval of time
- The cellulose thus obtained is a polymer of glucose units linked together in a beta- 1,4 linkage
Derivatives:
- Ester: esterification of cellulose yields products such as cellulose nitrate & cellulose acetate which are used in the preparation of films & plasticizers
- Ether: etherification yields products such as methyl cellulose, CMC, HPMC, HPC. The solubility of these polymers depends on the degree of substitution of hydroxyl group
Uses:
- Stabilizers, suspending agents & in ophthalmic solutions.