A rubber band (also known as an elastic band or gum band) is a loop of rubber, usually ring shaped, and commonly used to hold multiple objects together. The rubber band was patented in England on March 17, 1845, by Stephen Perry. Most rubber bands are manufactured out of natural rubber, and are sold in a variety of sizes.
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Manufacturing
Rubber bands are made by extruding the rubber into a long tube to provide its general shape, putting the tubes on mandrels, curing the rubber with heat, and then slicing it across the width of the tube into little bands. This causes the tube to split into multiple sections, creating a rubber band.
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Material
While other rubber products may use synthetic rubber, most rubber bands are primarily manufactured using natural rubber because of its superior elasticity.
Natural rubber originates from the latex of the rubber tree, which is acquired by tapping into the bark layers of the rubber tree. Rubber trees belong to the spurge family (Euphorbiaceae) and only survive in hot, humid tropical climates near the equator, so the majority of latex is produced in the Southeast Asian countries of Malaysia, Thailand, and Indonesia.
Once the latex has been tapped, and is exposed to the air, it begins to harden and become elastic, or rubbery.
Rubber band sizes
Measuring
A rubber band has three basic dimensions: length, width, and thickness. (See picture.)
A rubber band's length is half its circumference. Its thickness is the distance from the inner surface to the outer surface, and its width is the distance from one cut edge to the other.
If one imagines a rubber band during manufacture, that is, a long tube of rubber on a mandrel, before it is sliced into rubber bands, the band's width is decided by how far apart the slices are cut.
Size numbers
A rubber band is given a standard or quasi-standard number based on its dimensions.
Generally, rubber bands are numbered from smallest to largest, width first. Thus, rubber bands numbered 8-19 are all 1/16 inch wide, with lengths going from 7/8 inch to 3 1/2 inches. Rubber band numbers 30-34 are for width of 1/8 inch, going again from shorter to longer. For even longer bands, the numbering starts over for numbers above 100, again starting at width 1/16 inch.
The origin of these size numbers is not clear and there appears to be some conflict in the "standard" numbers. For example, one distributor has a size 117 being 1/16 inch wide and a size 127 being 1/8 inch wide. However, an OfficeMax size 117 is 1/8 inch wide. A manufacturer has a size 117A (1/16 inch wide) and a 117B (1/8 inch wide). Another distributor calls them 7AA (1/16 inch wide) and 7A (1/8 inch wide) (but labels them as specialty bands).
Thermodynamics
Temperature affects the elasticity of a rubber band in an unusual way. Heating causes the rubber band to contract and cooling causes expansion. Stretching a rubber band will cause it to release heat, while releasing it after it has been stretched will make it absorb heat, causing its surroundings to become cooler. This effect is due to the higher entropy of the unstressed state, which is more entangled and therefore has more states available. In other words, the ability to convert thermal energy into work while the rubber relaxes is allowed by the higher entropy of the relaxed state.
The result is that a rubber band behaves somewhat like an ideal monatomic gas in as much as (to good approximation) that elastic polymers do not store any potential energy in stretched chemical bonds. No elastic work is done to "stretch" molecules when work is done upon these bulk polymers. Instead, all work done to the rubber is "released" (not stored) and appears immediately in the polymer as thermal energy. Conversely, when the polymer does work on the surroundings (such as contracting to lift an object) it converts thermal energy to work in the process and cools in the same manner as an ideal gas, expanding while doing work.
Red rubber bands
In the UK during 2004, following complaints from the public about postal carriers creating litter by discarding the rubber bands which they used to keep their mail together, the Royal Mail introduced red bands for their workers to use: it was hoped that, as the bands were easier to spot than the traditional brown ones and since only the Royal Mail used them, employees would see (and feel compelled to pick up) any red bands which they had inadvertently dropped. Currently, some 342 million red bands are used every year.
Ranger bands
This type of rubber band was popularized by use in the military. Ranger bands are essentially sections of tire inner tubing cut into various sizes. They have the advantage of being versatile, durable, and resistant to weather and abrasion. They are commonly used for lashings, and can also be used for makeshift handle grips, providing a strong high-friction surface with excellent shock absorption.
Identical loops of inner tube are used by cave divers, and in that context are called Snoopy loops
Elastration
In animal husbandry, rubber bands are used for docking and castration of livestock. The procedure involves banding the body part with a tight latex (rubber) band to restrict blood flow. As the blood flow diminishes, the cells within the gonads die and dehydrate. The part eventually drops off.
Model use
Rubber bands have long been one of the methods of powering small free-flight model aircraft, the rubber band being anchored at the rear of the fuselage and connected to the propeller at the front. To 'wind up' the 'engine', the propeller is repeatedly turned, twisting the rubber band. When the propeller has had enough turns, the propeller is released and the model launched, the rubber band then turning the propeller rapidly until it has unwound.
One of the first to use this method was pioneer aerodynamicist George Cayley, who used rubber band-driven motors for powering his small experimental models. These 'rubber motors' have also been used for powering small model boats.
Source of the article : Wikipedia
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