Published on Apr 17, 2020
As a plastic material, rubber may be spread, cemented, calendered, molded, extruded, caulked, puttied, or wrapped into virtually any shape. Rubber can be coated on cloth, plastic, or metal; and sandwiched or forced into cracks.
An extremely tough material, rubber requires heavy machinery for forming and fabricating. The considerable heat generated during the mixing, mastication, grinding, and extruding processes must be dissipated and controlled. It also represents several energy management opportunities.
One of the earliest uses for rubber was for coating fabric to make it waterproof. Solutions or cements of rubber in solvents are easily spread on fabrics but, unless the ingredients necessary for cure and property control are included, the results may be quite unsatisfactory.
Rubber compounds are applied to fabric by calendering, i.e., rolling the rubber compound into the fabric on multi-roll calender machines. Tire cord is a special case in which cotton, rayon, nylon, or polyester cords are arranged in parallel and bound together by rubber on a calender.
Dough-like rubber compounds may be molded into virtually any shape, which is then retained by curing the compound in the mold. A good example is a tennis ball. To make one, a very high grade and resilient rubber compound is molded in "muffin tins" shaped as halves of the ball. These are then cemented together with a pill of a gas-releasing chemical inside the construction. It is then vulcanized to form the core of a ball, to which the fabric cover and proper nap fiber are cemented.
Weatherstrip, hose, inner tubes, tire treads, gaskets, channels, and many other rubber articles are fashioned by extrusion. The plastic compound used may be cured during the extrusion operation or at a later time.
The automobile tire serves as an excellent example. Each tire is built from wire, cord, fabric, and rubber into the doughnut shape which hugs the vehicle rim. The final product retains air for months or years, resists the heat built up by service and the attack of air, ozone, oils, and chemicals, and provides tens of thousands of miles of travel over roads and highways of all types and all of a highly abrasive nature.
Surprising to some, a tennis ball is a complicated structure for very rugged service.
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