Kraton is the trade name given to a number of high performance

elastomer An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus and high failure strain compared with other materials. The term, a portmanteau of ''elastic p ...

s manufactured by Kraton Polymers, and used as synthetic replacements for

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, and ...

. Kraton polymers offers many of the properties of natural rubber, such as flexibility, high traction, and sealing abilities, but with increased resistance to heat, weathering, and chemicals. It was first made by the chemical division of the

Shell Oil Company Shell USA, Inc. (formerly Shell Oil Company, Inc.) is the United States-based wholly owned subsidiary of Shell plc, a UK-based transnational corporation " oil major" which is amongst the largest oil companies in the world. Approximately 18,000 ...

in the 1950s, under the technical leadership of Murray Luftglass and Norman R. Legge. Shell sold its Kraton polymers business to private equity firm

Ripplewood Holdings Ripplewood is an American private equity firm based in New York City that focuses on leveraged buyouts, late stage venture, growth capital, management buyouts, leveraged recapitalizations and other illiquid investments. Ripplewood was founded ...

in March 2001.

Properties

Kraton polymers are styrenic

block copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are ...

(SBC) consisting of

polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...

blocks and rubber blocks. The rubber blocks consist of

polybutadiene Polybutadiene utadiene rubber BRis a synthetic rubber. Polybutadiene rubber is a polymer formed from the polymerization of the monomer 1,3-butadiene. Polybutadiene has a high resistance to wear and is used especially in the manufacture of tir ...

polyisoprene Polyisoprene is strictly speaking a collective name for Polymer, polymers that are produced by polymerization of isoprene. In practice polyisoprene is commonly used to refer to synthetic ''cis''-1,4-polyisoprene, made by the industrial polymerisa ...

or their hydrogenated equivalents. The tri-block with polystyrene blocks at both extremities linked together by a rubber block is the most important polymer structure observed in SBC. If the rubber block consist of polybutadiene, the corresponding triblock structure is: poly(styrene-block-butadiene-block-styrene) usually abbreviated as SBS. Kraton D (SBS and SIS) and their selectively hydrogenated versions Kraton G (SEBS and SEPS) are the major Kraton polymer structures. The microstructure of SBS consists of domains of polystyrene arranged regularly in a matrix of polybutadiene, as shown in the

TEM Tem or TEM may refer to: Acronyms * Threat and error management, an aviation safety management model. * Telecom Expense Management * Telecom Equipment Manufacturer * TEM (currency), local to Volos, Greece * TEM (nuclear propulsion), a Russian ...

micrograph. The picture was obtained on a thin film of polymer cast onto

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

from solution, and then stained with

osmium tetroxide Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite its toxicity and the rarity of osmium. It also has a number of unusual properties, one being that the ...

. The

glass transition temperature The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rubb ...

(T_g) of the polybutadiene blocks is typically −90 °C and T_g of the polystyrene blocks is +100 °C. So, at any temperature between about −90 °C and +100 °C Kraton SBS will act as a physically crosslinked

. If Kraton polymers are heated substantially above the T_g of the styrene-derived blocks, that is, above about 100 °C, like 170 °C the physical

cross-links In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...

change from rigid

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...

y regions to flowable melt regions and the entire material flows and therefore can be cast, molded, or extruded into any desired form. On cooling, this new form resumes its elastomeric character. This is the reason such a material is called a

thermoplastic elastomer Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) that consist of materials with both thermoplastic and elastomeric properties. ...

(TPE). The polystyrene blocks form domains of

nanometre 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...

size in the microstructure, and they stabilise the form of the moulded material. Depending on the rubber to polystyrene ratio in the material, the polystyrene domains can be spherical or form cylinders or

lamella Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal ...

e. The hydrogenated Kraton polymers named Kraton G exhibit improved resistance to temperature (processing at 200–230 °C is common), to oxidation and to UV. SEBS and SEPS due to their polyolefinic rubber nature present excellent compatibility with polyolefins and paraffinic oils.

Applications

Kraton polymers are always used in blends with various other ingredients like paraffinic oils, polyolefins, polystyrene, bitumen, tackifying resins, fillers to provide a very large range of end-use products ranging from hot melt adhesives to impact modified transparent polypropylene bins, from medical TPE compounds to modified bitumen roofing felts or from oil gel toys (including sex toys) to elastic attachments in diapers. It can make

asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

flexible, which is necessary if the asphalt is to be used to coat a surface that is below grade or for highly demanding paving applications like F1 racing tracks. Kraton based compounds are also used in non-slip knife handles. 1982 AMC Eagle 4-door wagon two-tone 07

The earliest commercial components using Kraton G (thermoplastic rubber) in the automobile industry were in 1975.

American Motors American Motors Corporation (AMC; commonly referred to as American Motors) was an American automobile manufacturing company formed by the merger of Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1, 1954. At the time, it was the ...

(AMC) used this polymer plastic on the

AMC Eagle AMC may refer to: Film and television * AMC Theatres, an American movie theater chain * AMC Networks, an American entertainment company ** AMC (TV channel) ** AMC+, streaming service ** AMC Networks International, an entertainment company *** ...

for the color matched flexible wheel arch flares that flowed into rocker panel extensions. Some grades of Kraton can also be dissolved into hydrocarbon oils to create "shear thinning" grease type products that are used in the manufacture of telecommunications cables containing optical fibres.

References

*
Kraton G SEBS and SEPS polymer official data documents and applications
retrieved on 6 May 2017. {{Authority control Polymers Copolymers Brand name materials