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Encyclopedia > Elastomer

The term elastomer is often used interchangeably with the term rubber, and is preferred when referring to vulcanisates. Elastomer comes from two terms, elastic (describing the ability of a material to return to its original shape when a load is removed) and mer (from polymer, in which poly means many and mer means parts). Each link of the chain is the "-mer" or basic unit that is usually made of carbon, hydrogen, oxygen and/or silicon. To make the chain, many links or "-mers" are hooked or polymerized together. They are amorphous polymers existing above their glass transition temperature, so that considerable segmental motion is possible. At ambient temperatures rubbers are thus relatively soft (E~3MPa) and deformable. Their primary uses are for seals, adhesives and molded flexible parts. Latex being collected from a tapped rubber tree Rubber is an elastic hydrocarbon polymer which occurs as a milky colloidal suspension (known as latex) in the sap of several varieties of plants. ... Vulcanization, or curing of rubber, is a chemical process in which individual polymer molecules are linked to other polymer molecules by atomic bridges. ... Polymer is the term used to describe large molecules consisting of repeating structural units, or monomers, connected by covalent chemical bonds. ... A material’s glass transition temperature, Tg, is the temperature below which molecules have little relative mobility. ... This article does not adequately cite its references or sources. ... Compression seal example A mechanical seal is a device which helps join systems or mechanisms together by preventing leakage (e. ... An adhesive is a compound that adheres or bonds two items together. ...

Contents

Background

A is a schematic drawing of an unstressed polymer. The dots represent cross-links. B is the same polymer under stress. When the stress is removed, it will return to the A configuration.
A is a schematic drawing of an unstressed polymer. The dots represent cross-links. B is the same polymer under stress. When the stress is removed, it will return to the A configuration.

Elastomers are usually thermosets (requiring vulcanization) but may also be thermoplastic (see thermoplastic elastomer). The long polymer chains cross-link during curing. The molecular structure of elastomers can be imagined as a 'spaghetti and meatball' structure, with the meatballs signifying cross-links. The elasticity is derived from the ability of the long chains to reconfigure themselves to distribute an applied stress. The covalent cross-linkages ensure that the elastomer will return to its original configuration when the stress is removed. As a result of this extreme flexibility, elastomers can reversibly extend from 5-700%, depending on the specific material. Without the cross-linkages or with short, uneasily reconfigured chains, the applied stress would result in a permanent deformation. [1] Image File history File links Polymer_picture. ... Thermosetting plastics (thermosets) refer to a range of polymer materials that cure, through the addition of energy, to a stronger form. ... A thermoplastic is a material that is plastic or deformable, melts to a liquid when heated and freezes to a brittle, glassy state when cooled sufficiently. ... A thermoplastic elastomer is a material which is both a thermoplastic (i. ... Vulcanization is an example of cross-linking. ...


Temperature effects are also present in the demonstrated elasticity of a polymer. Elastomers that have cooled to a glassy or crystalline phase will have less mobile chains, and consequentially less elasticity, than those manipulated at temperatures higher than the glass transition temperature of the polymer. [1]


It is also possible for a polymer to exhibit elasticity that is not due to covalent cross-links, but instead for thermodynamic reasons. Rubber elasticity, also known as hyperelasticity, describes the mechanical behavior of many polymers, especially those with crosslinking. ...


Mathematic justifications

Using the laws of thermodynamics, stress definitions and polymer characteristics (complete derivation in [1], pages103-105), we find ideal stress behavior:


sigma = n k T [ lambda _ 1 ^ 2 + lambda _ 1 ^ {-1} ]


where n is the number of chain segments per unit volume, k is Boltzmann's Constant, T is temperature, and is distortion in the 1 direction. The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. ...


These findings are accurate for values of up to approximately 400% strain. At this point, alignment between stretched chains begins to result in crystallization from noncovalent bonding. [1] This article needs to be wikified. ...


While Young's Modulus does not exist for elastomers due to the nonlinear nature of the stress-strain relationship, a "secant modulus" can be found at a particular strain. This article does not adequately cite its references or sources. ...


Examples of elastomers

Unsaturated rubbers that can be cured by sulfur vulcanization:

  • Natural Rubber (NR)
  • Polyisoprene (IR)
    • Butyl rubber (copolymer of isobutylene and isoprene, IIR)
    • Halogenated butyl rubbers (Chloro Butyl Rubber: CIIR; Bromo Butyl Rubber: BIIR)
  • Polybutadiene (BR)
    • Styrene-butadiene Rubber (copolymer of polystyrene and polybutadiene, SBR)
    • Nitrile Rubber (copolymer of polybutadiene and acrylonitrile, NBR), also called buna N rubbers
    • Hydrated Nitrile Rubbers (HNBR) Therban® and Zetpol®
  • Chloroprene Rubber (CR), polychloroprene, Neoprene, Baypren etc.

Saturated Rubbers that cannot be cured by sulfur vulcanization: Latex being collected from a tapped rubber tree Rubber is an elastic hydrocarbon polymer which occurs as a milky colloidal suspension (known as latex) in the sap of several varieties of plants. ... Latex being collected from a tapped rubber tree Rubber is an elastic hydrocarbon polymer which occurs as a milky colloidal suspension (known as latex) in the sap of several varieties of plants. ... Butyl rubber is a synthetic rubber, a random copolymer of about 98% of isobutylene with about 2% of isoprene. ... Polybutadiene is a synthetic rubber that has a high resistance to wear and is used especially in the manufacture of tires. ... Styrene Butadiene SBR (SBR) is a polymeride consisting of styrene and butadiene. ... Nitrile rubber is a synthetic rubber co-polymer of acrylonitrile (ACN) and butadiene. ... This article or section does not adequately cite its references or sources. ... Neoprene is the DuPont Chemical trade name for a family of synthetic rubbers based on polychloroprene. ...

  • EPM (ethylene propylene rubber, a copolymer faeces of polyethylene and polypropylene) and EPDM rubber (ethylene propylene diene rubber, a terpolymer of polyethylene, polypropylene and a diene-component)
  • Epichlorohydrin rubber (ECO)
  • Polyacrylic rubber (ACM, ABR)
  • Silicone rubber (SI, Q, VMQ)
  • Fluorosilicone Rubber (FVMQ)
  • Fluoroelastomers (FKM, FPM) Viton®, Tecnoflon®, Fluorel® and Dai-El®
  • Perfluoroelastomers (FFKM)Kalrez®
  • Polyether Block Amides (PEBA)
  • Tetrafluoro ethylene/propylene rubbers (FEPM)
  • Chlorosulfonated Polyethylene (CSM), (Hypalon®)
  • Ethylene-vinyl acetate (EVA)

Various other types of elastomers: EPDM rubber (ethylene propylene diene monomer rubber) is an elastomer which is characterized by wide range of applications. ... Silicone rubber is a polymer that has a backbone of silicon oxygen linkages, the same bond that is found in quartz, glass and sand. ... This article or section is in need of attention from an expert on the subject. ... Viton® is a synthetic rubber and fluoropolymer elastomer commanly used in o-rings. ... Tecnoflon is the brand of fluoroelastomers (FKM) and perfluoroelastomers (FFKM) manufactured by Solvay Solexis (former Ausimont). ... Kalrez is a perfluoroelastomeric material used in O-rings and gaskets. ... PEBA or Polyether block Amide is a thermoplastic elastomer (TPE) belonging to the technical polymers family. ... Ethylene-vinyl acetate (also known as EVA or sometimes simply as acetate) is the copolymer of ethylene and vinyl acetate. ...

  • Thermoplastic Elastomers (TPE), for example Hytrel®, etc.
  • Thermoplastic Vulcanizates (TPV), for example Santoprene® TPV
  • Polyurethane rubber
  • Resilin, Elastin
  • Polysulfide Rubber

A polyurethane is any polymer consisting of a chain of organic units joined by urethane links. ... Yep References and External Links Harnessing flea power to create near-perfect rubber, Media Release from the CSIRO Article published in Nature Shorter news item from Nature Summary from University of South Australia Insect Rubber article from Future Materials Categories: Biochemistry stubs | Proteins | Biochemistry ... Elastin, also known as elasticin, is a protein in connective tissue that is elastic and allows skin to return to its original position when it is poked or pinched. ...

References

  • Treloar L.R.G., The Physics of Rubber Elasticity, Oxford University Press, 1975. ISBN 0-19-85027-9.

[1] Meyers and Chawla. Mechanical Behaviors of Materials, Prentice Hall, Inc. (Pearson Education) 1999.

  • Budinski, Kenneth G., Budinski, Michael K., Engineering Materials: Properties and Selection, 7th Ed, 2002. ISBN 0-13-030533-2.
  • Explanation of properties and application of some elastomers: http://www.timcorubber.com/definitions/index.asp
  • Comparison table of elastomer properties: http://www.timcorubber.com/definitions/Comparison_to_Elastomer_Properties.pdf

  Results from FactBites:
 
Elastomer Analysis (0 words)
Determining the molecular weight distribution of elastomers (both natural and synthetic) is a very important analytical technique used to correlate with physical properties.
Elastomer formulations may be very complicated, with blends of polymers being used, as well as antioxidants, plasticizers, vulcanizers, accelerators, and a variety of fillers (carbon fl, titanium dioxide, silica, etc.).
Once again, two HR 5E’s and a single HR2 were used for the column bank, maintained at 75° C. In the case of elastomers, toluene is usually the solvent choice.
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