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Quality

Industry Standards
National Standards
ISO Standards

The distinction between industry, national, and international standards is for sake of conceptual clarity only. Industry standards are incorporated in national and international (ISO) standards. Testing for compliance under most domestic schemes shall follow ISO methodologies. ISO standards are used as such or implemented through incorporation in the national standards of individual countries.

Differences in types and grades are of major commercial significance. Indeed, the NR market is highly fragmented by types and, within each types, grades, with sizeable variations in trade flows and price movements.

Industry Standards

Two main grading systems exist:

1. Natural rubber graded by the conventional visual standards given in the "Green Book" of the International Rubber Quality and Packing Conference" (Visually Graded Types)
2. Natural rubber graded by technical specifications (Technically Specified Rubbers)

Specialty grades have been separately developed for rubbers with specialty applications.

Visually graded types

Conventional types of rubber (that is, rubber processed into sheet rubber and various crepes) are still visually inspected and graded according to quality and packing specifications set in the "International Standards of Quality and Packing for Natural Rubber Grades (The Green Book)". These standards were first issued and then revised within the framework of the "International Rubber and Packing Conference", comprising the world's leading rubber manufacturers, growers and trade associations. The grading system was based on the classification first developed in 1928 by the US "Rubber Manufacturers Association" (then "Rubbers Association of America").

Sheet and crepe rubbers intended for export shall be classified into one of the following grades:

Standard international grades of NR

• Ribbed Smoked Sheets (RSS)
  

Ribbed smoked sheets are graded on a visual basis as RSS IX, RSS 1, RSS 2, RSS 3, RSS 4 and RSS 5. After grading the sheets are packed in 50 kg bales, with the grades marked on the bales.

For more detailed information on RSS grading, please refer to the International Grade Descriptions for Sheet Rubber (Rubber Board, India).

• Crepe Rubber

Crepe rubber is either made from latex ("Latex Crepes") or processed from cup lumps, scrap and cuttings of ribbed sheet rubber ("Field Coagulum Crepes", or "Remilled Crepes").

Latex crepe is graded as "Pale Latex Crepe" (PLC, from fresh field latex) and "Sole Crepe" (SC, obtained from dried PLC). There are 8 grades under the PLC category, with the purest being 1X (the difference between tick and thin grades is only in thickness). Pale and sole crepes are more specialised than remilled crepes, and yield a higher premium. With both latex crepes, and especially the sole crepe, the colour represents an important element in marketing and pricing (a higher premium being obtained with a lighter coloured product).

Remilled crepe rubber prepared from field coagulum materials fall into five categories (further graded on a visual basis):

1. Estate Brown Crepe (EBC), thin and tick (made from lump and other high grade rubber scrap (field coagulam) generated on rubber estates) - 6 grades
   
2. Thin Brown Crepe (Remills), (derived from wet slab coagulum, unsmoked sheets and cup lumps) - 4 different grades
   
3. Thick Blanket Crepe (Ambers), (wet slabs, unsmoked sheets or other high grade scraps) - 3 grades
   
4. Flat Bark Crepe, (processed from all types of low grades scrap including earth scrap) - 2 grades
5. Pure Smoked Blanket Crepe, (exclusively derived from ribbed smoked sheet or cuttings)
   

For more information on the visual grading of crepe rubber, see the relevant section of the J&J Trade Links rubber grade section.

Technically specified rubber (TSR)

The conventional grading system outlined above had many disadvantages, in that it was based on subjective assessments and only recognised visual distinctions that could not have much technical significance. A major step towards evolving a more sophisticated classification for rubber was the development of a grading system strictly based on technical specifications. The move away from visual grading to technical specifications originated in Malaysia in the 1960s with the "Standard Malaysian Rubber" (SMR) scheme. This prompted producers in other countries (notably, Indonesia and Thailand) to develop similar technical specifications for grades. "Technically Specified Rubbers" (TSR) - that is, rubbers graded on the basis of technical parameters - now account for the bulk of traded rubber. Standardised international contracts for such rubber were first adopted by the International Rubber Association at its inaugural meeting on 24 September 1971.

Rubber is technically specified according to the following sets of rules, which are incorporated and detailed in the national standards of individual countries:

A- Technical specifications: TSR is graded on technical properties, rather than on visual distinctions. Technical parameters for grading are expressed as either maximum or minimum thresholds (detailed under national TSR schemes). For each grade, the dirt content, ash content, volatile matter content, nitrogen content, plasticity, and colour are tested by instruments. Testing for compliance shall follow ISO test methods.

ISO has specified 6 different grades of TSR, namely, TSR L (high quality and light coloured rubber prepared from latex), TSR CV (viscosity-stabilised high quality latex rubber), TSR 5 (good quality latex rubber, darker than TSR L), TSR 10 and 20 (good quality grades derived from field coagulum, suitable for general purpose uses), TSR 50 (up to 0.50 % wt dirt content). The specifications and characteristics of TSR are detailed in the following table.

TSR specifications

B- Packing specifications (specifications with regard to nominal dimensions and weight of bales and crates, as well as technical requirements for wrapping materials).

C- Registration (suppliers of TSR are required to apply for registration with the competent authority; TSR for shipments is to be accompanied by technical specifications issued by authorised laboratories; bales of TSR must be marked with the registered TSR symbol and the authorised grade).

The prime objective of the scheme was to standardise the marketing of new forms of natural rubber (block rubbers). However, conventional types of rubber (sheet rubber and crepe rubber) may also be graded on technical properties if they are supplied according to packing specifications and meet technical requirements.

Latex concentrate

Unlike sheet and crepe rubber, latex concentrate is graded according to detailed technical specifications (as for block rubber). Technical specifications are separately established by both the American Society for Testing Materials (ASTM) and the British Standards Institution (BSI). National and international standards are substantially identical in their requirements. Commercial latex is nowadays mainly prepared by centrifugation, with only two types made on a large scale:

1. HA (high-ammonia) latex, preserved with 0.7% ammonia
2. LA-TZ (low ammonia) latex, preserved with 0.2% ammonia + 0.025% TMTD/ZnO +0.04 - 0.05% lauric acid as ammonium laurate.

For more information on the grades of special purpose rubbers, please refer to Astlett Rubber's specialty grades page.

National Standards

Individual rubber producing countries are in charge of setting the acceptable limits for each grade of rubber they produce. The main rubber producing countries have their own schemes patterned after the TSR scheme. National schemes conform to specifications laid down by the International Standards Organisation (ISO).

Comparison chart

TSR CV	Constant viscosity grade
TSR L	Latex rubber
TSR 5	Sheet rubber
TSR 10	Field grade material
TSR 20	Field grade material

Source: Astlett Rubber

For more information on domestic rubber schemes, please refer to the following pages:

• Malaysian Rubber (Technical note, Department of Statistics Malaysia); Department of Standards Malaysia (subject index: standards for "Rubber", "Rubber latices", "Rubber latex concentrate")

• Indonesian Rubber (The R-S Information Center for Natural Rubber)

• Rubber Grades, India (M/s J&J Trade Links corporate page); Indian Rubber (The Rubber Board, statutory body constituted by the Government of India for the overall development of the rubber industry in the country)

• Papua Rubber Regulation
  

ISO Standards

To date, ISO's work has resulted in some 127 international standards for "rubber"; 55 standards for "latex and raw rubber"; 30 standards for "rubber compounding ingredients". Standards have been enacted for all the following fields:

ICS fields	Coverage
83.040	Raw materials for rubber and plastics
83.040.01	Raw materials for rubber and plastics in general
83.040.20	Rubber compounding ingredients (Including carbon black, kaolin clay, etc.)
83.060	Rubber
83.140	Rubber and plastics products (Including films and sheets, laminated sheets, hoses, seals, etc.)
83.160	Tyres (Including tubes and valves)
83.180	Adhesives
83.200	Equipment for the rubber and plastics industries

Source: UNCTAD secretariat (ISO Standards browsed by ICS fields)

ISO International Standards are voluntary, unless incorporated into domestic law. In practice, because they are developed in response to market demand, ISO standards tend to have wide industry application irrespective of whether they have been incorporated into domestic law or not.

Details of ISO International Standards for rubber and rubber products are listed in this section of the ISO website;
More on the ISO Technical Committee on rubber and rubber products.