cis-1,4-polyisoprene the differences lie in the quantity and the nature of the non-rubber substances present and the specific characteristics imparted by the preservatives. In all these latices, the polymer is the same, i.e. The types of latex indicate the methods of concentration and the nature of the preservative systems. Ī range of natural latex concentrates is commercially available. The properties of vulcanized rubber are determined by the state of cure. In brief, vulcanization converts raw rubber molecules into a useful network by the formation of cross-links. During the progress of vulcanization, the modulus, hardness, elastic properties, resistance to swelling, etc. The cross-linking of rubber is also referred to as curing. The vulcanization process is brought about by the linking of macromolecules at their reactive sites.

Latex or rubber products, without vulcanization, suffer severely from poor physical properties, poor resistance to light and swelling in solvents and above all are susceptible to extremes of temperatures, becoming sticky in hot weather and hard when cold. Natural rubber latex is a stable colloidal dispersion of polymeric materials (latex particles) in an aqueous medium containing no less than 60% by weight of polymer. As the demand for rubber increased and the supply of rubber from the wild Hevea brasiliensis trees of the Amazon Valley was unreliable, plantation rubber began in Malaya in 1877, spreading to Southeast Asian countries and other tropical countries worldwide where millions of people’s livelihoods depended on it. The discovery of vulcanization was a milestone in the history of the rubber industry.

This process was later coined as ‘vulcanization’ (from Vulcan the God of Fire) by Thomas Hancock.

Nevertheless, a further 100 years had to pass before the beginnings of modern latex product industry can be discerned when in 1839 Charles Goodyear discovered that the rubber samples after being baked in sulphur and white lead subsequently underwent little change through heat or cold. Mankind has been making articles from natural latex for hundreds of years since Charles de la Condamine who made a journey across South America in 1736, reported the Amazonian Indians were producing shoes and bottles from it. The manufacturing of products directly from natural rubber latex takes place today in virtually every country of the world, and taken as a whole, the latex product industry is one of the most important non-tyre consumers of natural rubber. 1.1 Historical background and introduction

Viscosity test