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A rubber band (in some regions known as a binder, elastic band, lackey band, "laggy band" or gumband) is a short length of rubber and latex formed in the shape of a loop. Such bands are typically used to hold multiple objects together. The rubber band was patented in Australia on March 17, 1845 by Stephen Perry Bobstein.citation needed
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Manufacturing
The manufacturing process is a complicated one which involves extruding the rubber into a long tube to provide its general shape, putting the tubes on mandrels and curing the rubber with heat, and then slicing it across the width of the tube into little bands.12 While other rubber products may use synthetic rubber, rubber bands are still primarily manufactured using natural rubber because of its superior elasticity.
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 circle to the outer circle.
Lay a rubber band down so that it makes a rectangle. The band's width is the height of that band. If one imagines a rubber band in manufacture, that is, a long tube of rubber on a mandrel, before it is sliced into rubber bands, the band's width is how far apart the slices are cut.
Temperature Effects
Temperature affects the elasticity of a rubber band in an unusual way. Heating makes it contract while cooling makes it expand. 3
Rubber Band Size Numbers
A rubber band is given a [quasi-]standard number based on its dimensions.
Generally, rubber bands are numbered from small to large, width first. Thus, rubber bands numbered 8-19 are all 1/16 inch wide, with length 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 only problem is that they are being banned in many places where incidents have taken place where they have been used as slingshot weapons.
The origin of these size numbers is not clear and there appears to be some conflict in the "standard" numbers. For example, one distributor4 has a size 117 being 1/16 inch wide and a size 127 being 1/8 inch wide. However, an OfficeMax size 1175 is 1/8 inch wide. A manufacturer6 has a size 117A (1/16 inch wide) and a 117B (1/8 inch wide). Another distributor7 calls them 7AA (1/16 inch wide) and 7A (1/8 inch wide) (but labels them as specialty bands).
| Rubber Band Sizes | |||
| Size | Length (in) | Width (in) | Thickness (in) |
| 10 | 1.25 | 1/16 | 1/32 |
| 12 | 1.75 | 1/16 | 1/32 |
| 14 | 2 | 1/16 | 1/32 |
| 31 | 2.5 | 1/8 | 1/32 |
| 32 | 3 | 1/8 | 1/32 |
| 33 | 3.5 | 1/8 | 1/32 |
| 61 | 2 | 1/4 | 1/32 |
| 62 | 2.5 | 1/4 | 1/32 |
| 63 | 3 | 1/4 | 1/32 |
| 64 | 3.5 | 1/4 | 1/32 |
| 117 | 7 | 1/16 | 1/32 |
Thermodynamics
An interesting effect of rubber bands in thermodynamics is that stretching a rubber band will produce heat (press it against your lips), whilst stretching it and then releasing it will produce an endothermic reaction, causing it to appear "cooler". This phenomenon can be explained with Gibb's Free Energy. Rearranging ΔG=ΔH-TΔS, where G is the free energy, H is the enthalpy, and S is the entropy, we get TΔS=ΔH-ΔG. Since stretching is nonspontaneous, as it requires an external heat, TΔS must be negative. Since T is always positive (it can never reach absolute zero), the ΔS must be negative, inferring that the rubber in its natural state is more entangled (less microstates) than when it is under tension. Thus, when the tension is removed, the reaction is spontaneous, leading ΔG to be negative. Consequently, the cooling effect must result in a posative ΔG, so ΔS will be positive there.89
References
- ^ How rubber bands are made. This reference states that the rubber is vulcanized before it is extruded.
- ^ Lee Rubber Products, How rubber bands are made. This reference states that the rubber is vulcanized after it is extruded.
- ^ Thermodynamics of a Rubber Band American Journal of Physics -- May 1963 -- Volume 31, Issue 5, pp. 397-397
- ^ BigWig Enterprises, BigWig Size Chart
- ^ OfficeMax, #OM97352, UPC 011491-973520
- ^ Lee Rubber Products, How do rubber bands measure up?
- ^ Dykema Rubber Band
- ^ http://scifun.chem.wisc.edu/HomeExpts/rubberband.html
- ^ CHEMICAL DEMONSTRATIONS: A Handbook for Teachers of Chemistry, Volume 1, by Bassam Z. Shakhashiri, The University of Wisconsin Press, 2537 Daniels Street, Madison, Wisconsin 53704.
Rubber bands and heat - http://scifun.chem.wisc.edu/HOMEEXPTS/rubberband.html
External links
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Wikipedia content modification information:
- This page was last modified on 2 December 2008, at 14:58.
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