Natural rubber in dry marketable forms were traded in earlier days based on visual assessment of quality only. This was a limitation for RSS and Crepe rubber with the end users. Hence efforts were made to grade natural rubber based on certain technical properties which could provide guarantees to the consumers of a certain minimum quality. The International Standards Organization (ISO) developed the first draft standards in 1964 in its meeting held in India for the grading and marketing of Block Rubber or Technically Specified Rubber (TSR).
The TSRs are mostly the block type made, adopting new methods of processing. . All the block rubbers are guaranteed to conform to certain technical specifications as laid out by the national schemes or by the ISO 2000 standards.
| Different Names of TSR | |
|---|---|
| STR | Standard Thai Rubber |
| SIR | Standard Indonesian Rubber |
| SMR | Standard Malaysian Rubber |
| SVR | Stanadar Vietnamese Rubber |
| ISNR | Indian Standard Natural Rubber |
| - | - |
| Different Grades of TSR | Indian Name |
|---|---|
| TSR 3 CV | ISNR 3 CV |
| TSR 3 L | ISNR 3 L |
| TSR 5 | ISNR 5 |
| TSR 10 | ISNR 10 |
| TSR 20 | ISNR 20 |
| TSR 50 | ISNR 50 |
The characteristics of the 6 grades as conceived in the ISO draft are as follows
This is a viscosity stabilized high quality grade, which provides a unique cost advantage in eliminating the pre mastication process and high reject rates.
It is a light colour rubber produced from high quality latex, having low ash and dirt content.
This grade of rubber is produced from fresh coagulum and or from un smoked sheets and air dried sheets. It process better specially in extrusion, calendaring and joining of cycle inner tubes .
his grade of rubber is produced from clean and fresh field coagulum or from un smoked sheets. It has good technological properties similar to those of RSS 2 and RSS 3 and has the advantage of lower viscosity and easier mixing characteristics.
It is a large volume grade of TSR, produced mostly from field coagulum and or a blend of field coagulum with lower grades of RSS and un smoked sheets. It has good processing characteristics and physical properties coupled with low viscosity and easier mixing characteristics.
It is the lowest grade of TSR and is produced from old dry field coagulum or partly de graded rubber. The rubber usually will have low viscosity, but have only lower technological properties.
| TSR Specifications for ISO 2000 | ||||||
|---|---|---|---|---|---|---|
| Parameters | TSR - CV | TSR - L | TSR - 5 | TSR - 10 | TSR - 20 | TSR - 50 |
| Dirt retained on 44 sieve (max % wt) | 0.05 | 0.05 | 0.05 | 0.10 | 0.20 | 0.50 |
| Ash content (max % wt) | 0.60 | 0.60 | 0.60 | 0.75 | 1.00 | 1.50 |
| Nitrogen content (max % wt) | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 | 0.60 |
| Volatile Matter (max % wt) | 0.80 | 0.80 | 0.80 | 0.80 | 0.80 | 0.80 |
| Initial Wallace Plasticity Po (min) | - | 30 | 30 | 30 | 30 | 30 |
| Plasticity Retention Index (min) | 60 | 60 | 60 | 60 | 60 | 60 |
| Plasticity Retention Index (min) | - | 6 | - | - | - | - |
The blocks are 33.33kg or 35kg bales in the international market and generally 25 kg bales in India. Kavanar Latex Ltd processes all the three types of bales. The bales will be wrapped in polythene sheets which are easily dispersible in rubber.
Each bale of TSR shall be marked indelibly with grade of rubber, net mass of bale, name of the producer and month and year of production