Technically Specified or Block Rubber (TSR)
Originally, most of the solid rubber used was in the form of ribbed smoked sheets or RSS rubber. By the early 1970s, however, TSR or rubber was introduced into the market.
TSR which is also known as block rubber is graded according to precise technical parameters such as dirt content, ash content, nitrogen content, volatile matter and properties of the rubber such as its Wallace Plasticity (PO) and its Plasticity Retention Index (PRI).
The TSR grades most widely used by the tyre and rubber industry are the TSR-20 and TSR-10 grades from Indonesia, Thailand and Malaysia which are known as SIR20, STR20 and SMR20 respectively. Block rubber can be produced both from field latex as well as from latex coagulum or what is commonly known as cup- lump. Tree lace and unsmoked sheets can also be used in producing block rubber.
Please see the Table below for a complete list of the all the major TSR grades commonly produced, the raw material from which they are produced and their properties.