Natural Rubber (NR) is produced from latex obtained from rubber trees in plantations. The most important forms in which NR is processed are the following: Sheets, Crepes, Block Rubber and Preserved Latex Concentrates.
Natural rubber (NR) processed into blocks adopting a new processing techniques is a notable improvement in the presentation of dry natural rubber. In India , block rubber is marketed with BIS specifications (IS4588 – 1986) and therefore, this rubber is termed as Indian Standard Natural Rubber (ISNR).
Two types of Sheet Rubber are produced and marketed in the international market, namely the Ribbed Smoked Sheets (RSS) and the Air Dried Sheets (ADS). Among these two types, Ribbed Smoked Sheet is the most popular and is available for consumption. There exist different grades of Ribbed Smoked Sheets rubber, namely RSS IX, RSS 1, RSS 2, RSS 3, RSS 4 and RSS 5.
|Conventional Grades of Ribbed Smoked Sheets||Used for the manufacturing||Equivalent ISNR(TSR) grades(which could replace conventional grades)|
|RSS - 1X||Aero tyres||ISNR - 3L|
|PLC - 1X||Injection bottle caps etc.||ISNR-3CV|
|RSS - 1||Tubes (NR)||ISNR - 5|
|PLC||Food Conveyer Belts etc.||ISNR-5|
|RSS - 2||Extruded hoses, Quality Footwear items||
ISNR - 10
|RSS - 3, RSS - 4||Tyres & Tubes, Tread Carcass, Off road tyres & ADV tyres, Extruded hoses, Footwear||ISNR - 10, ISNR - 20|
|RSS - 5||Cheap Items, handmade hoses||ISNR - 50|
|EBC||Cycle tyres, Footwear etc||ISNR-50|
|Technically Specified Crepe Rubber||Medical, Engineering, Retreading, Automobile and Footwear||ISNR - 5 & ISNR - 3|
Though Synthetic Rubber (SR) varieties have become available, demand for Natural Rubber (NR) always remains high. Following are some end products made from Natural Rubber.
- Conveyer Belts
- Rubber Mats
- Automotive Parts
- Rubber Intermediate
- Coating Material
- Surgical Gloves
- Industrial Gloves
- Elastic Thread
- Rubber Foam
- Coir Foam
- Carpet Backing
- Rubber Bands
RSS 1 refers to Ribbed Smoked Sheets, produced from natural rubber latex as ribbed sheets, by coagulation with acids and sheeting, properly air dried and smoked, and visually graded.
Ribbed smoked sheets (RSS) are graded based on visual assessment of quality. The International Rubber Quality and Packing Conference (IRQPC) have specified the grade descriptions, to establish acceptable grades for commercial usage.
Ribbed Smoked Sheets (RSS 3) is coagulated from high quality natural rubber latex produced by Thomson Rubbers. Rubber latex processed into ribbed rubber sheets and then sheeted, dried, smoked, and visually graded.
RSS3 rubber sheets are used in the production of Tyres (tires) & Tubes, Tread Carcass, Off road tyres & ADV tyres, Extruded hoses, Footwear etc. Tyre industry is the biggest consumer of RSS3 rubber sheets. The majority of rubber is exported as ribbed smoked sheets (RSS), (over 50%), of which ribbed smoked sheet no.3 ( RSS 3 ) constitutes the major part.
ISNR 20 (TSR 20) is general purpose Rubber graded by precise technical standards and not by visual characteristics. Some standards may vary marginally based on the origin. Technically Specified Rubber (TSR) is used for making tyres, tubes, rubber mats, cushion gum stock, raincoat proofings, micro-cellular sheet for upholstery and packing, conveyor belts, foot wear and various other rubber products.
TSR-20 has excellent processing characteristics and good physical properties. Its low viscosity and easier mixing characteristic(compared with the RSS grades) will reduce the mastication and mixing period considerably.
Thomson Rubbers offers ISNR20 (TSR20) rubber with following specifications:
|DIRT CONTENT, %BY MASS, MAX||0.2|
|VOLATILE MATTER % BY MASS, MAX||0.8|
|ASH CONTENT % BY MASS,MAX||1.0|
|NITROGEN ,% BY MASS ,MAX||0.6|
|INITIAL PLASTICITY, PO, MIN||30|
PLASTICITY RETENTION INDEX ,PRI, MIN
Before the early 1960’s rubber was produced in 3 forms – ECB, PLC & Sheet. The actual properties and grade of these were determined visually and was prone to human error. Later, the rubber industry started producing rubber with exactly known properties and specifications. Thus Technically Specified Rubber (TSR) grading system was established. I n India , it is called Indian Standard Natural Rubber (ISNR). ISNR (TSR) specification includes 7 grades: ISNR 3CV, ISNR 3L, ISNR 5, ISNR 10, ISNR 15, ISNR 20 (TSR 20) and ISNR 50
- ISNR: Indian Standard Natural Rubber
- TSR: Technically Specified Rubber
- ISNR-20 (TSR20) – Mostly manufactured from shell scrap, tree lace and cup lumps.
Skim Crepe (Skim Block) is a crinkly lace rubber, obtained when coagulated latex or any form of field coagulum (tree lace, shell scrap, earth scrap etc.) is passed several times through heavy rolls called crepers and then air dried at ambient temperatures. They are rapid-curing crepe or granulated (block) rubber containing a higher proportion of non-rubbers than ordinary sheet, crepe or block.
Estate Brown Crepe
Estate Brown Crepe (EBC) is produced in Blanket Form from lump and other high grade natural rubber scrap (field coagulam) generated in rubber estates. Power wash mills are used in milling these grades into a form of thick and thin crepes.