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Sunday, November 28, 2010

Rubber Bands

Ah, the familiar stretchy rubber band laid out on the countertop, waiting to be used, or just stretched, but surely it wasn't originally in that shape!

No, rubber bands start out as a milky colloid secreted by rubber trees. Colloids are basically substances evenly distributed throughout another substance, such as mayonnaise or fog. The colloids, or latex, in this case, are tapped, or extracted, from the tree. Next, on the rubber plantation, the latex is purified which removes impurities such as debris and tree sap. Now, the purified rubber is collected in large vats where it is combines with formic acid, causing the rubber particles to cling together in slabs. After this, the slabs of rubber and squeezed between rollers to remove excess water, and then pressed into blocks about 2 to 3 square feet, ready to be shipped to the rubber factory. In the rubber factory, the slabs are cut into small pieces, then mixed in a Banbury Mixer, invented by Femely H. Banbury in 1916. This machine mixes it with the pigments for color, sulfur for vulcanization, and other additives. Next, in the milling process, the rubber is heated, then squeezed flat in a milling machine. Later, once the rubber leaves the milling machine, it is slices up into strips. These strips are then fed to an extrusion machine which forces the rubber out in long, hollow tubes. The excess rubber collected at the head is then put back into the milling machine. Once the rubber is out of the extrusion machine, it is forced over long aluminum poles, called mandrels, which are covered with talcum poweder to keep the rubber from sticking. At this point, the rubber is still very brittle and in order to make it elastic and strong, it must be "cured." To do this, the poles are loaded onto racks that are steamed and heated inside a large machine. Onced the rubber is removed from the poles and washed to get rid of that white talcum powder, the rubes are fed into another machine that slices them up into the familiar band shape. Rubber bands tend to clump together, so they are typically sold by weight as it is more accurate to weigh small quantities at a time.

Rubber is usually subjected to a few quality tests before it is sold in the market. These tests commonly include moldulus (how hard the rubber band snaps back when pulled), elongation (how far the band will stretch), and break strength (how much strain a rubber band is able to withstand.)
Akron, Ohio was dubbed the Rubber Capital of the World, in fact, it's the home of the Goodyear Tire and Rubber Company. Rubber is mostly used to produce tires: see the connection? It hosts the annual Rubber Band Contest for Young Inventors.
Rubber was first named by the English chemist Joseph Priestly after noticing how dried pieces of rubber could rub away pencil marks.

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