Natural rubber is made from the sap of a tree.
Indians in South America used rubber hundreds of years ago.
Rubber trees grow in huge farms called plantations.
Thailand, Indonesia and Malaysia produce the most rubber.
Natural and synthetic rubber.
Natural rubber is made from the sap, called latex (say lay-tecks), of the rubber tree.
Synthetic rubber is manufactured from chemicals found in petroleum.
Rubber trees originated in Central and South America. The Indians collected drops of sap which oozed from the bark. When explorers first went there, they saw the Indians playing with rubber balls and using rubber in a number of ways..
Latex drips from cuts in the tree's bark
In 1735 a French explorer, Charles de la Condamine, took home some hardened rubber latex from Peru. In 1770 an English chemist discovered that the material rubbed out pencil marks, and so we get the name rubber. Scientists discovered that latex dissolved in turpentine made a liquid that could make fabric waterproof. In the 1820s English inventor Thomas Hancock built a machine that kneaded scraps of latex into a solid mass, and this led to the rubber processing of today. In 1832 Scottish chemist Charles Macintosh began making raincoats by putting a layer of rubber between two layers of cloth. This kind of coat is still called macintosh. Manufacturers started making rubber products, including shoes, elastic bands, hoses and tubes.
These early products got sticky in hot weather and stiff in cold. In 1839 American inventor Charles Goodyear discovered a way to make rubber stronger and less likely to be affected by seasons. He called the process vulcanisation, and it meant that rubber could be used in more products, such as between moving parts of machinery.
The invention of the automobile increased the demand for rubber, and by 1914 wild rubber plants could not supply enough. Until the 1870's most rubber came from Brazil and other parts of South America. In 1876 Sir Henry Wickham took some seeds to England and grew seedlings. The rubber tree seedlings were later planted in large farms called plantations, in Africa, Central and South America and in Asian countries such as Indonesia, Thailand, Vietnam and the Philippines. The cultivated rubber trees produce more latex than the wild trees. Today, more than 80% of the world's natural rubber is grown in Thailand, Indonesia and Malaysia.
A rubber tree seedling
Rubber trees grow best in hot, moist climates. The trees grow straight, 18-20 metres high with smooth bark and dark, shiny leaves. The tree has pale yellow blossoms, which give way to seed pods containing 3 brown seeds about 2-3 cm long. Latex containing rubber flows through the outer wood of the trunk, just under the bark.
A rubber plantation in Thailand
Workers called tappers collect the latex. They cut a shallow groove in the bark about one metre from the ground. At the bottom of the cut, a small spout is inserted into the tree, and a cup hangs below it to catch the drops of latex that ooze from the cut.
Trees are generally tapped every day for 15 days, then rested for 15 days. It takes about six years before a rubber tree is ready to be tapped.
In the past, an acid was added to the latex to make the sap set like a jelly. The latex jelly was then flattened and rolled into sheets and hung out to dry by workers.
A way of making rubber stronger and more elastic was invented by Charles Goodyear in 1839. His method was called vulcanising, and it stopped rubber from perishing.
Liquid latex is now shipped to factories where the rubber is made by machines. It can be coloured and made into many products. The latex is poured into tanks, and an equal amount of water is added. This liquid is strained to remove dirt. Formic acid is added to make the mixture form solid particles, which rise to the surface to form a crust of rubber. This is fed through rollers to squeeze out the water to make a solid sheet of rubber. This rubber is crude rubber, and is ready to be shipped to factories to be processed in different ways to make many different products.
Most rubber is used for tyres for cars, large vehicles and planes. Rubber is also used to make many mechanical parts such as gaskets, belts and seals.
Rubber products include waterproof clothing, gloves, hats, shoes and household products. Medical equipment made of rubber includes hot water bottles, gloves, syringes, tapes, oxygen tents, hearing aids and many more. Swimmers wear goggles,caps and flippers made of rubber. Many sports have rubber equipment, such as golf balls and other rubber balls. Rubber products seal jars, are used in toys and paints and for recreation. Sponge and foam rubbers are used to make bedding and other furniture, cushions and pillows, and as insulation.
Go to these sites to read more about natural rubber and the history of rubber
Go here to read about how a rubber tyre is made (note: in American spelling, tyre is spelt 'tire')
Read about recycling rubber tyres here
If you use any part of this, acknowledge this source in your bibliography like this:
Thomas, R. & Sydenham, S. Rubber [Online] www.kidcyber.com.au (2005)
Technology and Inventions
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