An elastomer is a

polymer A polymer (; Greek ''poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and ...

with viscoelasticity (i.e. both

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

and elasticity) and with weak intermolecular forces, generally low

Young's modulus Young's modulus E, the Young modulus, or the modulus of elasticity in tension or compression (i.e., negative tension), is a mechanical property that measures the tensile or compressive stiffness of a solid material when the force is applied ...

and high failure strain compared with other materials. The term, a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of words is often used interchangeably with

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, a ...

, although the latter is preferred when referring to vulcanisates. Each of the monomers which link to form the polymer is usually a compound of several

elements Element or elements may refer to: Science * Chemical element, a pure substance of one type of atom * Heating element, a device that generates heat by electrical resistance * Orbital elements, parameters required to identify a specific orbit of ...

among

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

and

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

. Elastomers are

amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal. Etymology The term comes from the Greek language ...

s maintained above their glass transition temperature, so that considerable molecular reconformation is feasible without breaking of covalent bonds. At ambient temperatures, such rubbers are thus relatively compliant ( E ≈ 3 M Pa) and deformable. Their primary uses are for seals, adhesives and molded flexible parts. Application areas for different types of rubber are manifold and cover segments as diverse as tires, soles for shoes, and damping and insulating elements. The importance of these rubbers can be judged from the fact that global revenues are forecast to rise to US$56 billion in 2020. Rubber-like solids with elastic properties are called elastomers. Polymer chains are held together in these materials by relatively weak

intermolecular bonds An intermolecular force (IMF) (or secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction or repulsion which act between atoms and other types of neighbouring particles, e.g. a ...

, which permit the polymers to stretch in response to macroscopic stresses. Polymer picture

Elastomers are usually thermosets (requiring vulcanization) but may also be

thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associat ...

(see thermoplastic elastomer). The long polymer chains cross-link during curing (i.e. vulcanizing). 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.

Examples

Unsaturated rubbers that can be cured by sulfur vulcanization: * Natural polyisoprene: cis-1,4-polyisoprene

natural rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, a ...

(NR) and trans-1,4-polyisoprene

gutta-percha Gutta-percha is a tree of the genus '' Palaquium'' in the family Sapotaceae. The name also refers to the rigid, naturally biologically inert, resilient, electrically nonconductive, thermoplastic latex derived from the tree, particularly fro ...

* Synthetic polyisoprene (IR for

isoprene Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an unsaturated hydrocarbon. It is produced by many plants and animals ...

rubber) * Polybutadiene (BR for

butadiene 1,3-Butadiene () is the organic compound with the formula (CH2=CH)2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two vin ...

rubber) * Chloroprene rubber (CR), polychloroprene, neoprene, Baypren etc. *

Butyl rubber Butyl rubber, sometimes just called "butyl", is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n, is the ...

(copolymer of isobutene and isoprene, IIR) ** Halogenated butyl rubbers (chloro butyl rubber: CIIR; bromo butyl rubber: BIIR) * Styrene-butadiene rubber (copolymer of styrene and butadiene, SBR) * Nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), also called Buna N rubbers **

Hydrogenated Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organi ...

nitrile rubbers (HNBR) Therban and Zetpol Saturated rubbers that cannot be cured by sulfur vulcanization: * EPM ( ethylene propylene rubber, a copolymer of ethene and propene) and EPDM rubber (ethylene propylene diene rubber, a terpolymer of ethylene, propylene and a diene-component) * Epichlorohydrin rubber (ECO) * Polyacrylic rubber (ACM, ABR) * Silicone rubber (SI, Q, VMQ) * Fluorosilicone rubber (FVMQ) * Fluoroelastomers ( FKM, and FEPM) Viton,

Tecnoflon FKM is a family of fluorocarbon-based fluoroelastomer materials defined by ASTM International standard D1418, and ISO 1629, ISO standard 1629. It is commonly called fluorine rubber or fluoro-rubber. FKM is an abreveation of Fluorine Kautschuk Mate ...

, Fluorel, Aflas and Dai-El * Perfluoroelastomers ( FFKM)

PFR, Kalrez, Chemraz, Perlast * Polyether block amides (PEBA) * Chlorosulfonated polyethylene (CSM), (Hypalon) * Ethylene-vinyl acetate (EVA) Various other types of 4S elastomers: * Thermoplastic elastomers (TPE) * The

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

s resilin and elastin * Polysulfide rubber * Elastolefin, elastic fiber used in fabric production * Poly(dichlorophosphazene), an "inorganic rubber" from hexachlorophosphazene polymerization

References

External links

Efficient and eco-friendly polymerization of elastomers, By Andreas Diener, Product Manager at List AG
{{Clothing materials and parts Materials science Polymer physics

Examples

See also

References

External links