Community Magazine December 2013

26 COMMUNITY MAGAZINE TUVIA COHEN We don’t want to worry you, but we have a little problem. You see, we have this rather large 350-ton jumbo jet that has requested permission to land. There are no other aircraft in the area, so we can easily give permission. The airplane has wheels, and plenty of them, so that doesn’t present any difficulties. The problem is that the captain of the jumbo has not yet decided what material to place around the metal rim of those numerous and ponderous wheels. Y ou have to visualize the situation to appreciate the scope of the problem. A jumbo jet is enormous in size, and as it descends from the sky to meet terra firma , it is traveling at some 200 miles an hour. As contact is made between the wheel rim and concrete, the friction created is intense. So quickly, suggest what he can use! Should he wrap the rims with sacking, a material which is usually very hard-wearing? It will rip to shreds in a second. Should he clothe the wheels in leather? The jolt caused by the impact will snap off the wheels as easily as a fragile twig. Perhaps he should simply leave the wheels in their pristine steel? Could you imagine the steel wheel carving a trench in the concrete, with sparks pouring forth, each spark posing the gravest risk? We have to find the solution, and quickly! While I think, my mind tires. Tires? You mean tires? That’s it! Rubber tires – the perfect solution. An inflated ring of rubber that covers the rim of the wheel will absorb the impact, and it is strong, durable, waterproof and flexible. The problem has been solved – what a relief! Could We Manage Without Rubber? Imagine that you had to describe this substance called rubber to a newcomer to Earth. What would you like to say? “Well, it’s sort of black and elasticated, you know, like . . . rubber!” But where does it grow, how is it made, who discovered it, why do we need it, and could we ever manage without it? The answer to the last question is a definite “no,” as anyone who has ever traveled in a car, plane, or bicycle will attest. Imagine the level of discomfort as you ride – or rather bounce and jolt – along the highway at 70 mph in a car with wheels bound by metal! As for the first questions, prepared to be amazed. Why is rubber so useful? There are many reasons. It holds air (as in your balloon), it keeps out moisture (as in your rubber boots), it does not readily conduct electricity (which explains its wide use in insulation), and is a poor conductor of heat (making it an excellent choice of materials with which to coat the handles of frying pans). But its chief importance to us is that it is elastic. In fact, rubber can be made so elastic that it will stretch to more than nine times its normal length. When you stretch a rubber band and let it go, its elasticity makes it quickly spring back to its original shape. A rubber ball, that mainstay of children’s games, bounces because of this same springiness. Your rubber heels are wonderful shock absorbers because of their elasticity. Fantastic stuff, rubber, but where does it come from? Columbus, the Indians, and Goodyear Tires When the early European explorers came to Central and South America, they saw the Indians playing with bouncing balls made out of rubber. According to an early Spanish historian, Columbus found the Indians using balls “made from the gum of a tree.” The explorers 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. Those same 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. It was not until the 18th century that two French scientists spent several years doing botanical research in South America. In 1730, one of them, Monsieur Francois Fresneau, made a full report about rubber, and was the first scientist to describe the rubber tree. Another major breakthrough took place in 1823, when a Scottish manufacturer, Charles Macintosh, had a brilliant idea for raincoats. He rubberized two pieces of cloth with dissolved rubber, and pressed them together, making a sort of cloth sandwich with a rubber filling. Although these coats became popular, they were not perfect, as the rain leaked in at the seams, and in hot weather, the rubber leaked out. While Mr. Macintosh was trying to perfect his raincoats, an American by the name of Charles Goodyear was attempting to produce rubber that would not be affected by changes of temperature. Then, one day in 1839, he accidentally placed a mixture of rubber, white lead and sulfur on a hot stove. When he removed it, he found that the rubber could still be stretched, but had not become gummy. Thus he discovered the process known as vulcanization, whereby sulfur is heated with rubber, resulting in a compound that remains tough and firm in both heat and cold. Vulcanized rubber was elastic, airtight, and watertight, and could be used to make tight seals between the moving parts of machinery. The rubber industry had begun. The Remarkable Rubber Tree