Technically specified rubbers

Characteristic Limits for rubber grades Test method 

---

Eield latex and field coagulum are the source materials for all varieties and grades of dry natural mbber that include the conventional International grades as weH as the Technically Specified Rubbers (TSR). 

This is the generic name for the scheme originally introduced in Malaysia as Standard Malaysian Rubber (SMR). In effect it is the same specification but apphed to rubber produced in other countries, e g., Standard Indonesian Rubber (SIR). Both SMR and SIR are Technically Specified Rubbers. 

Figure 14.8 Flow diagram for processing latex and field coagulum into technically specified rubber.

Global natural rubber consumption is split among tires (75%), automotive mechanical products (5%), nonautomotive mechanical products (10%), and miscellaneous applications such as medical and health-related products (10%). Since the 1960s, the quality and consistency of natural rubber has improved, primarily because of the implementation of standard specifications defining a range of grades of rubber. Natural rubber is available in three basic types technically specified rubbers, visually inspected rubbers, and specialty rubbers. 

Technically specified rubber is produced from intentionally coagulated and crumbled field latex, which is converted to a blanket and dried in an air circulating drying oven at 110-125°C. 

Natural rubber (technical specified rubber, TSR20) phr — 10.00 20.00 30.00 40.00... 

Block Rubbers Technically Specified Rubbers and Standard Technical Rubbers... 

The cup lump, tree lace, and earth scrap can be worked up into rubbers called brown crepes . These raw materials vary a great deal in quality and are often dirty, Preliminary treatment frequently includes soaking overnight in a dilute solution of sodium bisulfite to reduce the surface dirt and lighten the color. The material is then macerated and conveyed to a series of roll mills driven at friction speed and fitted with water sprays that clean up the rubber and blend it. The rubber is then sheeted off and dried like smoked sheet. Remilled blanket crepes refers to rubbers similar to brown crepes but which are made of smoked sheet cuttings, smallholders partially dried sheets, and other pieces. The production of brown crepes and remilled blanket crepe is diminishing as demand for technically specified rubber increases and technically specified rubbers use the same raw rubbers that go into crepes and blanket crepes. 

After World War II, rubber growers conducted surveys of customers to find out how their product could compete most effectively with the synthetic rubbers then available. As a result of these surveys, rubber producers developed technically specified rubbers. First introduced by Malaysia about 1965 as SMRs (Standard Malaysian Rubbers), they were accepted so well that other countries followed with similar products such as SIR (Standard Indonesian Rubber) and TTR (Thai Tested Rubber). 

Technically specified rubber grades of natural rubber used today by the industry are given in ASTM D2227. Commonly, these grades of natural rubber are based on dirt content. The more dirt removed from the natural rubber at the processing plant means the better price the natural rubber will receive in the marketplace. For exam-... 

---