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CHAPTER 4

The Production of Natural Rubber from Hevea brasiliensis Latex: Colloidal Properties, Preservation, Purification and Processing

Amongst the industrial elastomers, natural rubber (NR) latex from Hevea is the largest source of renewable elastomer. The NR plantation industry has evolved over the years from a largely agricultural based product to that of a technically specified industrial feedstock producer that supports a multitude of industries on rubber products for diverse applications. So far NR is the only successful commercial source of technical elastomer extracted from nature. The rest of the elastomers are manufactured from monomers obtained from crude oil. The major NR producing countries are concentrated in South-East Asia and south Asia, producing more than 80% of the world's NR in their smallholdings and well-managed plantations. In this chapter a brief history of the development of the Hevea NR industry will be described and contrasted with that of the synthetic rubbers. The latex collected from the trees is a colloidal dispersion containing rubber hydrocarbon particles in addition to non-rubbers of biological origin. The colloidal properties of the NR latex and how its stability and preservation is affected by the biological components of the latex will be highlighted. The methods of purification and concentration of field latex into technically specified latex for the dipping industry are elaborated. Solid rubbers are produced from field latex or from a blend of latex and collected field coagula. Depending on the cleanliness of the source materials, different grades of crepe rubbers, sheet rubbers and block rubbers are produced. More than 80% of NR produced is block rubbers which are technically specified (TSR) as opposed to the visually graded sheet and crepe rubbers. The acceptance of these technically specified rubbers as standard rubbers for the global market on par with the synthetics is clear proof of their quality. Special grades of latices and rubbers including those chemically modified such as epoxidized NR (ENR) are produced to meet special product or processing needs. Some recent advances in addressing the rubber protein allergy issue in medical gloves, in searching for benign, safe, hazard-free accelerators and preservatives for latex; and measures in addressing the nitrosamines in rubber products will be dealt with in some detail. The diverse applications of latex and solid rubbers are also covered, highlighting some niche application areas where NR excels over the synthetics. The role of NR in moving forward to a low-carbon society would be briefly touched on.

Print publication date: 05 Dec 2013
Copyright year: 2014
Print ISBN: 978-1-84973-610-7
PDF eISBN: 978-1-84973-764-7
From the book series:
Polymer Chemistry Series