When the early European explorers came to central and South America, they saw the Indians playing with bouncing balls made of rubber. According to an early Spanish historian, Christopher Columbus found the Indians of Haiti using balls “made from the gum of a tree”.
The explorers also learned that the Indians made “waterproof” shoes from latex, the milky white juice of the rubber tree. They spread the latex on their feet and let it dry. The Indians also made waterproof bottles by smoothing latex on a bottle-shaped clay mold. They dried the latex over a fire, and then washed out the clay. For many years the Spaniards tried to duplicate the water resistant products (shoes, coats and capes) of the Native South Americans, but they were unsuccessful. Rubber was merely a museum curiosity in Europe for the next two centuries.
An Indian soaking his feet in latex
In 1731 the French government sent the mathematical geographer Charles Marie de La Condamine to South America on a geographical expedition. In 1736, he sent back to France several rolls of crude rubber, together with a description of the products fabricated from it by the people of the Amazon Valley. The French called this new material Caoutchoc, the French pronunciation of the Indian word cahuchu, which means weeping wood. General scientific interest in the substance and its properties was revived.
In 1770 the British chemist Joseph Priestley discovered that rubber can be used to erase pencil marks by rubbing, the property from which the name of the substance is derived. In 1791 the first commercial application of rubber was initiated when an English manufacturer, Samuel Peal, patented a method of waterproofing cloth by treating it with a solution of rubber in turpentine. The British inventor and chemist Charles Macintosh, in 1823, established a plant in Glasgow for the manufacture of waterproof cloth and the rainproof garments that have since borne his name.
Then in 1839, in America, Charles Goodyear (1800-60) discovered by accidentally dropping on a hot a piece of rubber that had been treated with sulfur, that when rubber and sulfur are heated together at a high temperature a rubber with the desirable properties result. This process, called vulcanization is still the basis of the rubber manufacturing industry.
Vulcanization by Charles Goodyear in 1839
The next great advance in rubber technology came a decade later with the invention of the accelerated-aging oven for measuring rubber deterioration. This oven duplicated, in a few days, the results of years of normal use. It enabled rubber technologists to measure rapidly the deterioration caused by various conditions, especially exposure to atmospheric oxygen. The use of these ovens led scientists to add chemical agents called antioxidants to the rubber; this prolonged the useful life of heavy rubber articles such as automobile tires. Within a few years, new chemical compounds were created that markedly slowed the deterioration of soft rubber goods such as gloves, sheeting, and tubing.
Another development in rubber technology involved the use of uncoagulated latex. Methods were developed of extruding rubber in fine threads for use in the fabrication of textiles, such as those used in elastic undergarments, and also of electroplating rubber on metals and other materials.
In the United States, rubberized goods had become popular by the 1830s, and rubber bottles and shoes made by the Native South Americans were imported in substantial quantities. Other rubber articles were imported from England, and in 1832, at Roxbury, Massachusetts, John Haskins and Edward Chaffee organized the first rubber-goods factory in the United States. However, the resulting products, like the imported articles, became brittle in cold weather, and tacky and malodorous in summer. In 1834 the German chemist Friedrich Ludersdorf and the American chemist Nathaniel Hayward discovered that the addition of sulfur to gum rubber lessened or eliminated the stickiness of finished rubber goods. In 1839 the American inventor Charles Goodyear, using the findings of the two chemists, discovered that cooking rubber with sulfur removed the gum's unfavorable properties, in a process called vulcanization. Vulcanized rubber has increased strength and elasticity and greater resistance to changes in temperature than unvulcanized rubber; it is impermeable to gases, and resistant to abrasion, chemical action, heat, and electricity; vulcanized rubber also exhibits high frictional resistance on dry surfaces and low frictional resistance on water-wet surfaces.
Natural rubber production begins with the collection of latex, a milky white substance produced by the cells of several plants. Through an initial cut and selective removal of bark, a rubber tree will yield approximately 1.8 kg (about 4 lb) of dry crude rubber annually. About 250 trees are planted per hectare (100/acre), and the annual yield for ordinary trees is about 450 kg/hectare (400 lb/acre) of crude rubber. In specially high yield trees, the annual yield may range as high as 2225 kg/hectare (2000 lb/acre), and experimental trees that yield 3335 kg/hectare (300lb/acre) have been developed.
Workers on a plantation begin by drawing latex from trees in a method called tapping. Once the milky liquid latex is tapped and collected, it is placed in a treatment tank where the liquid will begin to gel, or coagulate, into a more solid form. Then, in a roller mill, the gel is pressed between rollers to consolidate the rubber into 0.6 cm (0.25 in.) slabs or thin sheets, called crepe. Finally, the rubber is then air- or smoke-dried, and baled for shipment to manufacturers.
In on a plantation begin by drawing latex from trees in a method called tapping. Once the milky liquid latex is tapped and collected, it is placed in a treatment tank where the liquid will begin to gel, or coagulate, into a more solid form. Then, in a roller mill, the gel is pressed between rollers to consolidate the rubber into 0.6 cm (0.25 in.) slabs or thin sheets, called crepe. Finally, the rubber is then air- or smoke-dried, and baled for shipment to manufacturers
The mixture is then applied mechanically to a base or is shaped, and the coated object or shaped mixture is placed in molds and vulcanized.
The wild rubber trees of the South American jungles continued to be the main source of crude rubber for most of the 19th century. In 1876 the British explorer Sir Henry Wickham collected about 70,000 seeds of H. Brasiliensis, and, despite a rigid embargo, smuggled them out of Brazil. The seeds were successfully germinated in the hothouses of the Royal Botanical Gardens in London, and were used to establish plantations first in Ceylon (now Sri Lanka) and then in other tropical regions of the eastern hemisphere. Similar plantations have since been established, largely within a narrow belt extending about 1100 km (about 700 mi) on both sides of the equator. About 99 percent of plantation rubber comes from southeastern Asia. Attempts to establish significant rubber plantations in the tropical zone of the western hemisphere have failed because of widespread tree loss as a result of a leaf blight.
To gather the latex from plantation trees, a diagonal cut angled downward is made through the bark; this cut extends one-third to one-half of the circumference of the trunk. The latex exudes from the cut and is collected in a small cup. The amount of latex obtained on each tapping is about 30 ml (about 1 fl oz).
Thereafter, a thin strip of bark is shaved from the bottom of the original cut to retap the tree, usually every other day. When the cuttings reach the ground, the bark is permitted to renew itself before a new tapping panel is started.
In S.E. Asia, the rubber tapping season typically begins around the end of April and lasts, until the end of February. The period between February and April, is known as “wintering”, when the rubber trees shed their leaves and the weather is too dry and thus, unsuitable for tapping of rubber.
We depend so much on rubber that it would be almost impossible to get along without rubber. Rubber is especially useful for several reasons. It holds air, keeps out moisture and does not conduct electricity. But its chief importance to us is that it’s elastic. When you stretch a rubber band and let it go, it springs back, to its original shape. Your rubber heels absorb shock when you walk because they have elasticity.
Manufacturers use rubber to make everything from waterproof aprons, boots, raincoats, gloves, hats, automobile spare parts and tires, hair combs and doctors use it for hot water bottles, ice bags, syringes, elastic tapes and surgeon’s gloves. Hearing aids, oxygen tents and many other pieces of equipment have rubber parts.
Infact, it has become an indispensable part of our life. It would be impossible to imagine life without rubber – for example, could you imagine the tires of a car made of any other material other than rubber? Literally thousands of products that we use and see everyday are made of different kinds of rubber. As rubber is really a dynamic and versatile element, it can be used to make almost any thing.
Some of the common products that are made of rubber are: tires. baby toys, gloves, condoms, shock absorbers, watches, underwater equipment, garments, boots, rubber bands, car mats, machine parts, erasers and sporting equipments.
The coefficient of friction of rubber, which is high on dry surfaces and low on wet surfaces, leads to the use of rubber both for power-transmission belting and for water-lubricated bearings in deep-well pumps.