More and more in social life, but also throughout the modern industries (even in the so-called “rubber industries”, there exist many irritations about the correct use of the terms Rubber, Caoutchouc, Latex and Elastomer. The following essay should be a guidance to distinguish and to use the correct terms.

Today : Rubber Products

Among the generally known industrial applications such as the tyre industry, erasers and birth control, elastomers also find widely use in so-called RUBBER PRODUCTS (rubber gaskets, rubber profiles, rubber mats, rubber-metal-bonds, rubber hoses...) and in rubber-metal-bonding (vibration damping, noise damping,...).
Rubber products are predominantly made by extrusion, die-cast, compression mould, centrifuge process and foaming.
Due to the advanced technological development the properties of the Elastomers can be adjusted to nearly any necessary application.

History and Nomenclature/Terminology

The term Caoutchouc comes from the Indian word "cahuchu" = crying tree. Excavations show that rubber balls were already used for ball games during the Mayan ages (11^th century). It is assumed today that Columbus brought the first balls of rubber to Europe. Records from 1755 describe the harvesting/extraction of rubber from the chyle of trees by natives in the Amazon area.

The English word “India Rubber” seems to originate from the British chemist Priestley, who already demonstrated in 1770 that pencil-lines could be erased with rubber, and as soon as 1772 the first rubber cubes were sold in England and France as erasers.

Around 1880 the Englishman Henry Wickham smuggled seeds of rubber plants (Hevea Brasiliensis) though England to India and started the first plantations. At the turn of the century these Indian plantations broke the monopoly of Brazilian “wild” rubber, for the harvests were extremely fertile.

The word rubber is used today meaning high polymer plastics, which get highly elastic through vulcanization.

Today Natural Rubber (NR) is distinguished from variable Synthetic Rubbers. Both rubber groups are basis for so-called Elastomers.

Natural Rubber is mainly extracted from Latex, a milky sap from the trunk of the Hevea Brasiliensis (Euphorbiceae, spurge family).
The name Hevea Brasiliensis comes from a rampant growing tree in the Amazonian territory, which can grow as high as 20 m with a trunk circumference of 80 cm.
Nowadays the tree is grown on plantations in almost all tropical areas, especially in huge plantations in India, but also in Africa and South America.

Latex is a milky-white emulsion of rubber droplets, derived by cutting/scoring the trunk of Hevea Brasiliensis. Through various processes the latex coagulates, with the raw rubber separating from the water.
Natural Rubber is elastic and can be stretched to 5 times its own length. It is lighter than water and has almost no scent. Natural Rubber is a bad heat and electricity conductor. Natural Rubber turns into a technically valuable product through vulcanization, during which sulphur attaches to the double bonds of the rubber molecules. The resulting product is usually called “rubber”, which is much more durable against air and chemicals than raw rubber.

Various types of Rubber

The big group of composition rubbers (rubber mixtures) include:

- Styrene Butadiene Rubber (SBR)
- Chloroprene Rubber (CR)
- Ethylene Propylene Diene Rubber (EPDM)
- Acrylic Nitrile Rubber (NBR)
- Fluorinated Rubber (FPM)
- Silicon Rubber (Q, VQM)
- Polyurethane (PU)
and many more.

All these products are part of the group “Elastomers”, but differ considerably in their chemical and physical properties.
Together with “Thermoplastics” the Elastomers belong to the group of “Polymers”.

Author : U. Siegfried Grunow, European Rubber Research Inst., July 2006, © ERRI
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