In botany , gums ( the , plural gums , Latin cummi and Greek kómmi , Coptic ⲕⲟⲙⲙⲓ, which “ goes back to ancient Egyptian ḳmj.t ”) are certain plant saps ( exudates ) that emerge from injured areas. These dispersions contain various heteropolysaccharides and other substances that harden more or less elastically in air and form sticky solutions in contact with water.
In nature, rubber is used to protect the tree, because it seals injured areas against disease. Examples of gums are gum arabic (resin from African acacia species), tragacanth and karaya gum . Some gums are used as emulsifiers or thickeners for food or cosmetics. The natural rubber is sometimes called rubber elasticum , but is not a rubber in the sense of botany or technology.
In technology , the vulcanizates of natural and synthetic rubbers are referred to as rubber ( the , plural rubber ) . Vulcanization produces elastic and relatively hard-wearing (soft) rubbers, the elastomers . A very high degree of vulcanization of rubbers, however, leads to thermosets . These non-elastic, rigid materials are sometimes referred to as hard rubbers or ebonites . The first commercially usable synthetic rubber was styrene-butadiene rubber , other economically important synthetic rubbers are, for example, butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), ethylene propylene diene rubber (EPDM) , Chloroprene rubber (CR) and polyisoprene rubber (IR).
Rubber as a material
As industrially manufactured elastomers, rubbers are generally vulcanized. Unvulcanized rubbers are usually thermoplastics . Some synthetic rubbers are also used in the manufacture of thermoelastic plastics . Natural rubbers are tough, elastic, amorphous, self-sticking materials and are practically useless as a material. In the traditional way, the macromolecules of the rubbers are covalently cross-linked by adding sulfur under pressure and heat . The specialty of a rubber is that it can be stretched under tensile load and returns to its original shape without load. Below the thermal decomposition, rubbers cannot be deformed by melting. The shaping therefore takes place before or during the vulcanization process. If rubber freezes, it is as hard as glass and breaks brittle under load.
In order to improve the properties and processability, rubbers are often used as mixtures and mixed with additives. For example, vulcanization accelerators and retarders, dyes, fillers, antioxidants or anti- ozone agents are added. Car tires are mixed with man-made carbon black (to improve abrasion behavior, tear resistance and light resistance). The black coloration results from this. In the course of vulcanization, rubbers can also be foamed using blowing agents.
Elastomers are used in many areas. These include car tires , drive belts , conveyor belts , O-rings , rubber boots , shoe soles , special protective clothing and gloves, rubber bands and erasers . Foam rubbers are used as vibration dampers and for heat and sound insulation .
Over time, rubber materials and everyday objects age. The cause for this is the effect of oxygen , heat, ozone , light or mechanical stress. In order to slow down aging processes, anti-aging agents such as phenylenediamines or phenols are added.
Colloquial meanings of the term
"Rubber" also has special slang meanings:
- Rubber as a synonym for elastic band .
- Rubber as a synonym for resin or collective term for rubber resin or natural resin
- Gum as a short form for hair tie .
- Rubber as a synonym for condom .
- "Give rubber!" = Senseless accelerating - so make sure that a thick black line ( rubber abrasion ) remains on the road, or is colloquially meant "hurry up".
- My children “play rubber” in an abbreviated form when they want to play rubber twists .
- "Rubber" or "office rubber" as a German-Swiss joke designation for "office staff", from French : commis , "commercial clerk, sales assistant".
- “Rubber eagle” as a joke for poultry that has been grilled too long and is therefore tough.
- “Rubber eagle” as a Swiss-military joke for the functional badge of older uniforms made of plastic and attached to the armpit loop.
- "Rubber suit", e.g. B. as fetish clothing , water sports or protective suit, usually also incorrectly used as a synonym for comparable items of clothing made of neoprene , PVC or PE-coated materials.
- The gummy bear (and other gummy candies ) are not made from rubber , but from edible thickeners with rubber-like properties, e.g. B. gelatin , modified starch or gum arabic made.
- "Rubber boat" as a synonym for inflatable boat (although today it is often made of soft PVC ).
- " Rubber pants ", z. B. as fetish clothing ( rubber fetishism ), as trousers for anglers ( waders ) or as waterproof diaper pants , mostly also incorrectly used synonymously for comparable panties made of PVC or PE -coated materials.
- "Rubber paragraph" for a vaguely defined, easily abusive law.
- " Rubber doll " Synonym for sex doll (although most of these are made of soft PVC these days).
- " Padded cell ", a padded room in which psychiatric patients cannot injure themselves during attacks of rage.
- “ Eraser ”, a specially formulated rubber with which pencil or ink marks can be removed from paper and other carrier media.
- Properties of the elastomers - resistance list (PDF; 578 kB)
- Udo Maid-Kohnert: rubber . In: Lexicon of Nutrition . Spectrum Academic Publishing House, Heidelberg 2001/2002.
- GUMMI, m., N. Origin and form. Duden.de
- Angelika Fallert-Müller: Rubber . In: Lexikon der Biochemie , Spektrum Akademischer Verlag, Heidelberg 1999/2000.
- Jürgen Falbe, Manfred Regitz (ed.): CD Römpp Chemie Lexikon , Thieme, Stuttgart, 1995.
- Fritz Röthemeyer, Franz Sommer: Rubber technology. 2nd Edition. Carl Hanser Verlag, Munich / Vienna 2006, ISBN 978-3-446-40480-9 , pp. 93-106.
- Ceresana: Market Study Synthetic Elastomers ( Memento of March 18, 2015 in the Internet Archive ), June 2013, archive.org.
- Werner Baumann: Rubber and rubber. Springer-Verlag, 2013, ISBN 978-3-642-58916-4 , p. 382 ( limited preview in Google book search).