GRADESNatural Rubber (NR) is produced from the milky white liquid called latex, harvested from rubber trees by the process of tapping. Latex is a dispersion of rubber in water. The latex that flows out from the rubber tree on tapping, is channeled into an attached container, mainly polythene cups. Around 80% of the crop from rubber plantation is in the form of latex.
The Latex which gets dried up on the tapping panel (tree lace) and the collection cups (shell scrap) also form part of the crop and are called field coagulum. It is collected by the tapper in a basket just before tapping. About 20 % of the total crop from rubber plantation is in the form of field coagulum.
Latex and field coagulum are highly susceptible to degradation due to bacterial contamination on keeping. Hence they are processed into different marketable forms of natural rubber.
The most important forms of Natural Rubber marketed are Sheet Rubber (both RSS and ADS), Technically Specified Block Rubber (TSR), Crepe Rubber, Preserved Latex Concentrates, and Specialty Natural Rubber.
Among these, the first three are in dry form and almost 90% of the total Natural Rubber produced in the world is at present marketed in these types. In the international market, these three broad types are available in over 40 grades, mainly consisting of Ribbed Smoked Sheets (RSS) and Technically Specified Rubber (TSR) in block form.
The fourth type Preserved Latex Concentrates is produced in all important rubber-growing countries and about 10% of world production of Natural Rubber is processed and marketed in this type.
Besides these 4 types, there are a number of Speciality Natural Rubbers which include Natural Rubber in liquid form as well as in chemically modified forms and in blends and composites.The details of each type of Natural Rubber with the grades involved and the grade description are given seperately.