A BRIEF HISTORY OF NATURAL RUBBER

The peculiar properties of caoutchouc were first discovered and exploited by South American natives. Early writings dating back to the fifteenth and sixteenth century mention a tree (Hevea Brasiliensis) called by local people ‘CAHUCHU‘, namely, weeping wood, because it secreted a sort of latex, hence our word caoutchouc (actually coming from its identical French counterpart).

They also reported that the natives used to play with a ball that bounced much better than any other thing known to Europeans. The ball was made of that same white, milky liquid obtained by tapping those trees. As it dried up, the liquid coagulated, forming a dense elastic mass. Later, Europeans learned how the natives used this remarkable material for a number of other purposes; they smeared it onto their clothes to make them waterproof and molded it into various shapes to obtain elastic objects.

Till then there had never been a truly elastic, waterproof and airtight material. Chemists and firefighters had to make do with leather fire hose where each seam leaked; boots and raincoats were never really waterproof.

To Europeans, the main problem was that they seemed utterly incapable of preserving caoutchouc. There was no way to carry liquid latex to Europe, because it would not last long enough without deteriorating. It had to be dried up, but then it was too dense and hard for further workings. So the king of Portugal sent his boots to Brazil just to have them proofed.

Several attempt to exploit dried-up rubber followed. In 1770 the English chemist and naturalist Joseph Priestley pointed out that rubbing a piece of…rubber on a paper sheet was a way to erase pencil marks. This is actually why we call it rubber in English: because it could be used to rub writings away.

Meanwhile, a French chemist, Macquer, began to make rubber hose smearing a rubber solution onto wax mold. Another Frenchman, Grossart, tried to do the same softening rubber strips with turpentine and wrapping them around glass mold. 1803 saw the establishment of the first industrial RUBBER production plant in Paris. They made rubber bands used for braces and garter suspenders. All these products present two drawbacks: in the first place, they were quite sticky at normal temperatures and became even stickier as the temperature rose; second, they hardened and stiffened whenever it was cold.

In 1823, in England, Thomas Hancock found that caoutchouc, so tenacious and sinewy, could be rolled to make it easily malleable, thus developing what we now call the mixing and mastication process. This made raw rubber more malleable, yet the question of withstanding high and low temperatures was far from solved. Studies on this subject went on, until an American –Charles Goodyear – came up with vulcanization.

THE DISCOVERY OF VULCANIZATION

The American Charles Goodyear had been trying to age rubber adding different substances to it. It was only in 1839 that he finally found how a heated mixture of caoutchouc, sulphur and white lead lost all stickiness. This kind of curing, later called “VULCANIZATION”, was only patented in 1844.

Mastication and vulcanization became the basis of the rubber industry, since they made it possible to exploit caoutchouc as raw matter for rubber items. In 1888, the Belfast veterinarianJohn Boyd Dunlop patented his invention – the rubber tire. It was a well-timed discovery, fit to support the development of the automobile industry. Making and selling more and more cars also meant making and selling an increasing number of tires. The outcome was, of course, the threat of a worldwide shortage of caoutchouc, for until the end of the XIX century the sole source of natural rubber was to be found in the rubber trees spontaneously growing in Brazil.

RUBBER TREE PLANTATIONS

In 1876, Sir Henry Wickham carried some 70,000 seeds of Hevea Brasiliensis (or rubber tree) from Brazil to his homeland. Only 2,600 of them sprouted, less than 4%. Before the end of 1876 the shoots were sent to Ceylon (nowadays Sri Lanka) and planted in the local Botanical Gardens. The trees that grew up in the island were later transplanted to Malaysia and Indonesia(currently the largest producers of rubber latex together with Thailand).

Until the beginning of our century, however, the new plantations, still slowly growing, could not help meeting the European demand for rubber. Natural rubber, owing to skyrocketing industrialization and motorization, began to run out, causing – naturally enough – a price hike.
It is therefore quite understandable that the chemical industry hoped to find a solution through the production of some sort of synthetic rubber. This dream was eventually to come true thanks to chemists like Williams (an Englishman who invented isoprene), Bouchardat in France, Tilden in England, Wallach and F.Hoffman in Germany and Kondakov in Russia.

RUBBER PRODUCTION IN THAILAND

A “Hevea Brasiliensis” tree (or rubber tree) photographed in a plantation in the Thai island of Kho Chang. You can see the plastic vessel used tocollect rubber latex. After a deep gash has been made on the tree, the liquid begins to drop into these small containers. Sometimes, plastics is replaced by coconuts, once the nut has been emptied. This is where the millions of tons of rubber latex exported and distributed to all international markets come from.

To people interested in the rubber industry, a visit to a rubber tree plantation is an amazing and exciting experience. Some plantations are engulfed by an almost impassable forest, others are more accessible, being located along roads, and feature countless evenly arranged rows of trees as far as the eye can see.

Rubber trees give their best and most abundant latex in a ripe age, between 5 and 20 years. Afterwards, the plantation must be renovated, because continual exploitation would lead to a natural impoverishment of their latex

Once rubber latex has been collected, it is carried to these tiny laboratories (often located in the middle of the forest). Here, impurities are removed and some chemicals are added; the latex is then poured into these small makeshift mixers driven by hand. Small local producers of natural rubber latex, like these at Kho Chang, still do not avail themselves of electric machinery. These candid rubber sheets are going to be hung up somewhere to dry them up.

Another stage of the mixing process. This snow-white latex has already undergone some treatment and has been hung to dry in the sun. It will remain there as long as necessary; the drying stage shall then continue in roofed rooms where it shall be sheltered from the recurring tropical showers as well as from the implacable sun.

After the first mixing stage, rubber is hung up on a fence to dry under the sun. Removing the moisture contained in rubber is vital to obtain a good product.

In rooms like this rubber is hung to dry, protected from direct sunlight. By then it has already lost most of its moisture and has taken a golden or yellowish hue: soon it will be ready for packaging and shipping on battered old barges towards Bangkok’s markets and hence to all other destinations.

Such antediluvian mixers are very common in Thailand. Entirely human-powered via a sturdy handle, they are used by small rubber latex producers in the first stage of mixing. The coarse milling of the surface of its roll helps in spreading out latex sheets.

The second picture shows the robust handle, the only mechanical device needed and used to drive the roll. The same rolls are also used to lay down rubber in the shape of the typical white sheets seen in the background.



   

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