The National Geographic describes Natural
Rubber (NR) as the nature’s most versatile vegetable crop. Grown in the
Amazonian rain forest as ‘wild rubber’, Hevea Brasiliensis was well
established as a major plantation crop in a number of countries in Asia
and Africa during the 19305. Now it is cultivated in the world in around
100 Lakh hectares and the world production of NR was over 50 Lakh MT
during 1990-91. .NR finds use in the production of more than 35000
articles required for a variety of applications in industry,
agriculture, transportation and communication, health and family
planning,sports etc.,
The crop from a rubber
plantation consists of two items namely the latex and the’ scrap’
rubber. Latex which accounts for about 80'" of the crop from a rubber
plantation is an aqueous dispersion of rubber containing a number of
non-rubber constituents like proteins, carbohydrates, phospholipids,
etc. The amount of NR present in field latex varies depending on factors
like age of tree, system of tapping, nutrient status of the soil,
season, etc., and on an average the dry rubber content (drc) is
30-40',4.
The term’ scrap’ rubber indicates a
mixture of materials like tree lace, cup lump, earth scrap, etc., which
account for about 20% of the crop. Latex and scrap rubber are processed
into a number of marketable forms of NR like the preserved field latex,
latex concentrates, ribbed smoked sheet, crepe rubber and block (crumb)
rubber to meet the specific requirements of the rubber consuming
industry viz., the latex and dry)’ rubber products manufacturing
sectors. The latex properties which have significance in product
manufacture are dry rubber content, nonrubber solids content,
Mechanical Stability Time, Volatile Fatty Acid number, the potassium
Hydroxide number, alkalinity and viscosity whereas in the case of dry
rubber, the molecular weight and its distribution, Mooney- Viscosity
plasticity, Plasticity Retention Index~ Dirt content, Volatile Matter,
etc., are more important.
Composition and Structure of NR
Grading And Packing Of Rubber
