Rubber

Rubber – Hevea brasiliensis

The milky sap of rubber trees was being tapped by native Indians when the Spanish arrived in South America in the early 1500s.

In the West its use would escalate with the production of cars and their tyres at the start of the 20th century. 

History

It was as the product of the Amazonian tree Hevea brasiliensis, the Pará rubber tree, that became the most popular source of the bouncy rubber used for waterproofing and ball games that we are familiar with today.

Native Indians were enslaved on cruel plantations in Amazonia and the Belgian Congo. This exposed the seamier side of colonial industry with its unregulated market and rubber barons living on vast riverside estates built on slave labour. Atrocities prompted the first human rights movement that led to general concerns about genetic piracy – the exploitation of the resources of foreign countries by wealthy nations. By 1912 the Brazilian industry had collapsed in competition with the industry that had developed in Southeast Asia.

Plant geography

The British government decided to experiment by setting up plantations elsewhere but an initial attempt in Calcutta failed in the unsuitable climate.

Henry Wickham, a pioneer, adventurer and entrepreneur who was familiar with the rubber tree in Amazonia, was selected by Kew’s Joseph Hooker to collect seed which would be germinated at Kew and the seedlings shipped eventually to Southeast Asia. It was agreed that Wickham be paid £10 per 1000 seeds by the government. In 1876 Wickham provided Kew with 70,000 seeds of Para rubber collected from trees on the River Tapajos in Brazil. Three weeks later 2700 seeds ad germinated, and soon 1919 plants of Hevea brasiliensis and 32 Castilla elastica were handed over to George Thwaites, an Englishman now superintendent of the botanical gardens at Peradeniya in Sri Lanka, of these 1700 arrived in Henarathgoda Gardens near Colombo a month later. Immediately after Wickam’s return Kew gardener Robert Cross was sent to Brazil for more seed and more plants were sent to Sri Lanka and, the following year, to Singapore.  Here Henry Ridley, an English botanist, geologist and naturalist promoted the establishment of rubber tree plantations on the Malay Peninsula.

In Singapore Henry James Murton who had joined Kew as a gardener in 1873 became Superintendent of the Singapore Botanic Gardens from 1875 to 1880. Here he exchanged plants with Kew and with Ridley devising a way to speed up the selection and propagation of the plants without using seed. Notably, it was Murton who received from Kew the first seedlings of Para rubber in 1879. Most of the rubber in Malaya has come from this original introduction. He was followed as director of the Singapore Botanic Gardens by another Kewite, Nathanial Cantley.^[1]

It is not certain whether the trees growing in Southeast Asia were originally collected by Wickham or Cross but they are the ancestors of most of the naturally-produced rubber today. Plants were also sent to the Dutch Botanic garden at Bogor.

Plants were also sent by Hooker to Jamaica, Cameroon, Montserrat, Singapore, and Queensland. Those in Singapore and their offspring were inherited by Henry Ridley when he became Director of Gardens and Forests in Singapore in 1888. He conducted large-scale experiments at the Singapore Botanic Gardens, measuring the yield and trialling different ways of extracting the latex. A vulcanizing rubber factory was set up in Singapore and it was here that the first rubber tyres were made. By 1930 about 1.2 million ha of rubber plantation had been established on the Malay Peninsula and by 1930 this was the world’s major supplier followed by the Dutch East Indies and Sri Lanka – Brazil now a minor player.

By the early 20th century plantations in Malaya and Sri Lanka were losing momentum and in 1896 a Chinese plantation owner Tan Chay Yan set up 16 ha at Bukit Lintang, near Malacca to be followed by others as rubber production moved out of Brazil into Southeast Asia.^[2]

Processing & products

Among the various rubber products are the original chewing gum extracted from the Mesoamerican Manilkara Tree, Manilkara zapota; gutta-percha used to insulate electrical wires; the rubber used in golf balls; condoms; and of course the rubber in the tyres of bicycles, cars, and aircraft.

European use of rubber became possible when Americans Charles Goodyear and Thomas Hancock in 1839 found that by heating the latex with sulphur and lead oxide it would lose its unmanageable stickiness to become dry, pliable and long-lasting at high and low temperatures, a process known as vulcanization. It was later found that by using organic solvents rubber could be moulded into different forms and used to impregnate fabrics to provide waterproofing.

In 1909 a German team from the Bayer laboratory in Elberfeld, Germany, successfully polymerized isoprene, the first synthetic rubber and this was followed by others using coal tars and petrochemicals especially through World War II.

Botany

Rubber is derived from the sap (latex) of the rubber trees, mostly Castilla elastica from Central America, Hevea brasiliensis from the Amazon forest of South America, and Ficus elastica of southern and southeast Asia.

Latex, we believe, is the plant’s defence against attack from herbivores and disease and it is contained in special latex vessels in the plant. At least 2000 plants produce rubber-like latex. Trees are tapped by making V-shaped cuts in the tree trunk and collecting the latex in a cup set at its base. We now know that many plants produce different forms of rubber latex as volatile hydrocarbons called isoprenes.

Timeline

c. 500 – Aztec and Mayan civilizations known to use latex ‘cahuchu’ (hence the French caoutchouc) to waterproof clothing and dwellings. Rubber collected in gourds was rolled into a ball and used in ritual games called ulama as observed by Spanish in the early 1500s.
1751 – French naturalist Charles Marie de la Condamine with botanist François Fresneau publishes a scientific paper on the properties of natural rubber.
1770 – Joseph Priestley coins the name ‘India-rubber’ or ‘rubber’ after seeing caoutchouc sold in cubes for artists to rub out lead pencil lines.
1823 – Charles Macintosh invents a rainproof coat, popular with hackney-cab drivers, from two fused pieces of rubber cloth and an inner layer of rubber – and known as the ‘Macintosh’.
1839 – Charles Goodyear creates vulcanized rubber.
1853 – Traders take advantage of the invention of steamships and penetrate the Amazon in search of rubber supplies
1860 – Rubber price at a high – equivalent to that of silver
1869 – James Collins identifies Para rubber as the most resilient form of rubber
1876 – Henry Wickham provides Kew with 70,000 seeds of Para rubber collected from trees on the River Tapajos in Brazil. Three weeks later 2700 seeds ad germinated, and soon 1919 plants were off to Sri Lanka with 1700 arriving in Henarathgoda Gardens near Colombo a month later
1876 – Immediately after Wickam’s return Kew gardener Robert Cross was sent to Brazil for more seed and more plants sent to Sri Lanka and, the following year, to Singapore
1888 – Henry Ridley conducts large-scale experiments into rubber at Singapore Botanic Gardens and encourages the establishment of plantations.
1888 – John Dunlop invents the pneumatic rubber bicycle tyre.
1892 – William Tilden synthesizes rubber from synthetic isoprene in the UK.
1895 – Michelin introduces the first pneumatic motorcar tyre.
1950s – The last wild rubber is exported from Brazil.
1959 – The production of synthetic rubber overtakes that of natural rubber.
1990 – Around five billion Hevea brasiliensis trees are now producing rubber on plantations around the world.
2006 – Natural rubber production is 9,680,000 tonnes for the year. Synthetic production is 12,762,000 tonnes.