Rubber band: Difference between revisions
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{{About|the common household item|other meanings|Rubber band (disambiguation)}} |
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{{Redirect|Elastic band|the band and orchestra|The Elastic Band|the first aid bandage|elastic bandage}} |
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[[Image:Elastic money.jpg|thumb|Five rubber bands]] |
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A '''rubber band''' (in some regions known as a '''binder''', an '''elastic''' or '''elastic band''', a '''lackey band''', '''laggy band''', '''lacka band''' or '''gumband''') is a short length of [[rubber]] and [[latex]] formed in the shape of a loop. |
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Rubber bands are typically used to hold multiple objects together. The rubber band was patented in [[England]] on March 17, 1845 by [[Stephen Perry]].<ref>{{Citation |
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|title=The Hancocks of Marlborough: Rubber, Art and the Industrial Revolution - A Family of Inventive Genius |
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|year= 2009 |
|year= 2009 |
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|page= 89 |
|page= 89 |
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Revision as of 14:40, 13 January 2011
lolInventive Genius
|year= 2009 |page= 89 |first= John |last= Loadman |first2= Francis |last2= James |url= http://books.google.com/books?id=K7Qb_og24WYC&pg=PA89&dq=%22Messers+Perry+and+Co%22&lr=&cd=1#v=onepage&q=%22Messers%20Perry%20and%20Co%22&f=false |isbn= 978-0199573554 |doi= }}</ref>[1][2]
Manufacturing
Rubber bands are made by 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.[2][3]
Material
While other rubber products may use synthetic rubber, rubber bands are primarily manufactured using natural rubber because of its superior elasticity[2].
Natural rubber originates from the sap of the rubber tree. Natural rubber is made from latex which is acquired by tapping into the bark layers of the rubber tree. Rubber trees belong to the spurge family (Euphorbiaceae) and live in warm, tropical areas. Once the latex has been “tapped” and is exposed to the air it begins to harden and become elastic, or “rubbery.” Rubber trees only survive in hot, humid climates near the equator and so the majority of latex is produced in the Southeast Asian countries of Malaysia, Thailand and Indonesia.
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.
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.
Rubber Band Size Numbers
A rubber band is given a [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 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 origin of these size numbers is not clear and there appears to be some conflict in the "standard" numbers. For example, one distributor[4] has a size 117 being 1/16 inch wide and a size 127 being 1/8 inch wide. However, an OfficeMax size 117[5] is 1/8 inch wide. A manufacturer[6] has a size 117A (1/16 inch wide) and a 117B (1/8 inch wide). Another distributor[7] 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
Temperature affects the elasticity of a rubber band in an unusual way. Heating causes the rubber band to contract, and cooling causes expansion.[8]
An interesting effect of rubber bands in thermodynamics is that stretching a rubber band will produce heat (press it against your lips), while stretching it and then releasing it will lead it to absorb heat, causing its surroundings to become 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, implying that the rubber in its natural state is more entangled (fewer 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 positive ΔG, so ΔS will be positive there.[9][10]
Red rubber bands
In 2004 in the UK, following complaints from the public about postal carriers causing 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.[11]
Model use
Rubber bands have long been one of the methods of powering small free-flight model aeroplanes, 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 earliest to use this method was pioneer aerodynamicist George Cayley, who used them for powering his small experimental models. These 'rubber motors' have also been used for powering small model boats.
See also
References
- ^ March 17 - Today in Science History
- ^ a b c How rubber bands are made. This reference states that the rubber is vulcanized before it is extruded. The rubber is then "cured" on mandrels.[unreliable source?][failed verification] The "Made How" reference appears to directly copy text from other sources, some of which appears to be incorrect. The exact same text regarding Thomas Hancock appears in a 1995 book entitled "CD's, super glue and salsa: how everyday products are made" by Kathleen Witman, Kyung-Sun Lim, Neil Schlager. Contradicting other sources, both credit Thomas Perry rather than Stephen Perry for the invention of the rubber band.
- ^ Lee Rubber Products, How rubber bands are made. This reference states that the rubber is vulcanized after it is extruded.
- ^ BigWig Enterprises, BigWig Size Chart
- ^ OfficeMax, #OM97352, UPC 011491-973520
- ^ Lee Rubber Products, How do rubber bands measure up?
- ^ Dykema Rubber Band
- ^ "Thermodynamics of a Rubber Band", American Journal of Physics, 31 (5): 397–397, May 1963
- ^ http://scifun.chem.wisc.edu/HomeExpts/rubberband.html
- ^ Shakhashiri, Bassam Z. (1983), Chemical Demonstrations: A Handbook for Teachers of Chemistry, vol. 1, Madison, WI: The University of Wisconsin Press, ISBN 978-0299088903
- ^ The Times: "Posties' red rubber bands stretch public's patience"
Rubber bands and heat - http://scifun.chem.wisc.edu/HOMEEXPTS/rubberband.html
External links
