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By Arup K.Chandra & PK Mohamed

Rubber is one of the most essential materials in our daily life. Rubber finds its application in many products such as tyres, tubes, conveyor belts, rubber bearings for bridges, automotive components etc.

The story of rubber goes back to the 14th century when Christopher Columbus made his second journey to America. He noticed that the natives were playing with a round object, which when thrown against a surface bounced back. He found out that the round object was made from a material secreted by a particular tree called Ulli or Ule in Central America.

It was the secretion that is today called latex and the material was named “rubber” by Joseph Priestley in the 18th century because of its inherent ability to erase or rub out lead marks.

In the 18th century rubber grew in its utility through the efforts of Thomas Hancock, a London coach builder, who in 1820 devised the first equipment to dissolve rubber in solvents to make items like gloves and shoes. However, these items were susceptible to the slightest changes in temperature.

This was further refined by the invention of the process of vulcanization by American Charles Goodyear in 1839. Subsequently, the process of vulcanisation, which was enhanced first by adding sulphur, later got accelerated by Oen Slanger in 1906 by introducing Aniline as an accelerator. The work continued in this direction and the properties of rubber compounds like ageing, weathering, colouring, reinforcing and processing were improved by mixing additional compounding ingredients.

The innovation and development of new rubber and rubber chemicals and selection of these basic materials helps us to come up with new rubber products that ease our life.

A close review of this table clearly reveals that development is taking place in all areas of technology and can be clubbed under three major heads – namely materials, technology and manufacturing. The major developments that are taking place in all these areas will be covered in the subsequent write-ups.

Material development

Today most of the rubber products that we use have undergone a series of changes over the decades to meet the never ending customer demands to accommodate new application. These efforts have now graduated too many very high-tech products.

In order to support these demands all round developments have taken place in the materials front. The importance of materials is growing more distinct in today’s rapidly changing world –be it an elastomer, new generation nanofiller, reinforcing materials like aramid, carbon fibre, nitrosamine free vulcanization and vulcanizing agents, a series of post-vulcanisation stabilizers and environmental friendly process oil.

Polymers / elastomers

Natural rubber is a highly valuable biomaterial in contrast with other bio-polymer. It cannot be replaced by other synthetic materials for many vital applications like heavy duty truck-bus, aircraft tyres as well as many other latex products. It is the first choice for heavy duty radial truck tyre manufacturers, especially because of its physical and mechanical properties and excellent adhesion to steel cord.

A major concern of all tyre and rubber manufacturers has always been the shortage and spiralling prices of natural rubber (NR), except recently. The short supply of NR is due to production cut and shifting towards palm oil cultivation in major NR producing countries like Malaysia, higher usage of NR in commercial vehicle radial tyre and growing demand in the fast developing economies like China and India. NR is also vulnerable to the effects of climate change, pollution, population growth, and economic development.

These issues give rise to fluctuations in the market both with respect to price and availability. Unless alternatives are identified and developed on a commercial scale, tyre and rubber companies would experience great difficulties in the days to come. This is exactly why the scientist / technologist community and other stakeholders across the globe are currently making all out efforts to find a partial or full alternative to natural rubber.

Guayule, Dandelion etc

Necessity is of course ‘the mother of invention’. In other words, ‘crisis is the criteria for new developments’. About 40% of the world’s NR production is consumed by USA and Japan. The last decade saw huge ups and downs in NR prices leading to a renewed interest in developing alternative crops for natural rubber production.

There are as many as 1,800 species identified that could produce natural rubber latex, but only a few of these are known to produce large amounts of high molecular weight rubber.

Guayule, a desert shrub growing in semi-arid regions in Mexico and southern US, is one of the non- tropical plants that have been at the centre-stage of all experiments to develop a commercial alternative source of NR. Other promising plants are Russian Dandelion, sunflower or lettuce. Scientists are also considering the synthesis of synthetic poly-isoprene through bio-isoprene route.

The company leading the commercialization of guayule as an industrial crop is Yulex Corporation, founded by Daniel R. Swiger. Yulex Corporation manufactures and produces guayule rubber for medical devices and specialty consumer products that are safe for people who have latex allergy.

Another company Pan Aridas has cultivated proprietary, high-yielding lines of guayule with agricultural operations concentrated in Arizona. Guayule’s viability as a potential biofuel has been enhanced recently since it does not adversely affect the world’s agricultural production. Guayule has benefit over food crops as biofuel – it can be grown in areas where food crops would fail.

Dandelion rubber was first discovered and industrially cultivated in 1930s and 1940s by the Soviets in Central Asia, Ukraine and Russia. This was also grown in USA and Canada in 1940s.

Perennial plants produce high quality NR comparable to Hevea. Latex is contained in canals in plant tissue. Latex extraction is based on Soviet technology. It involves cutting the roots into slices and letting the latex flow into the extraction buffer and centrifugation.

Germans, Russians and Americans produced rubber from this plant during the Second World War. Ten to 20 per cent of the plant’s carrot-like root is rubber-ready. Once it is cut, latex seeps out, albeit it is difficult to use as it polymerizes immediately.

Scientists from the Fraunhofer Institute for Molecular Biology and Applied Ecology have identified the enzyme responsible for the rapid polymerization and have switched its flow off. Now, if the plant is cut, the latex flows out instead of being polymerized. Using this method we can obtain four to five times the amount we would normally get.

If the plants were to be cultivated on a large scale, every hectare would produce 500 to 1000 kilograms of latex per growing season.

(;; Global R&D Centre-Asia, Apollo Tyres, India)

(Appeared on February-March 2018 issue of Tyre Asia. The second part of Tech Notes will appear in the April-May issue of Tyre Asia)

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