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Polybutadiene utadiene rubber BRis a synthetic rubber. Polybutadiene rubber 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 a ...
formed from the
polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many f ...
of the
monomer In chemistry, a monomer ( ; '' mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification ...
1,3-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 v ...
. Polybutadiene has a high resistance to wear and is used especially in the manufacture of tires, which consumes about 70% of the production. Another 25% is used as an additive to improve the toughness (impact resistance) of plastics such as polystyrene and acrylonitrile butadiene styrene (ABS). Polybutadiene rubber accounted for about a quarter of total global consumption of synthetic rubbers in 2012. It is also used to manufacture golf balls, various elastic objects and to coat or encapsulate electronic assemblies, offering high electrical resistivity. The
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
refers to polybutadiene as poly (buta-1,3-diene). Buna rubber is a term used to describe an early generation of synthetic polybutadiene rubber produced in Germany by Bayer using sodium as a catalyst.


History

The Russian chemist Sergei Vasilyevich Lebedev was the first to polymerize
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 v ...
in 1910. In 1926 he invented a process for manufacturing butadiene from ethanol, and in 1928, developed a method for producing polybutadiene using
sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
as a
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
. The government of the Soviet Union strived to use polybutadiene as an alternative to natural rubber and built the first pilot plant in 1930, using ethanol produced from potatoes. The experiment was a success and in 1936 the Soviet Union built the world's first polybutadiene plant in which the butadiene was obtained from petroleum. By 1940, the Soviet Union was by far the largest producer of polybutadiene with 50,000 tons per year. Following Lebedev's work, other industrialized countries such as Germany and the United States developed polybutadiene and SBR as an alternative to natural rubber. In the mid-1950s there were major advances in the field of
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
s that led to the development of an improved versions of polybutadiene. The leading manufacturers of tires and some
petrochemical Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewabl ...
companies began to build polybutadiene plants on all continents; the boom lasted until the 1973 oil crisis. Since then, the growth rate of the production has been more modest, focused mainly to the
Far East The ''Far East'' was a European term to refer to the geographical regions that includes East and Southeast Asia as well as the Russian Far East to a lesser extent. South Asia is sometimes also included for economic and cultural reasons. The t ...
. In Germany, scientists from Bayer (at the time a part of the conglomerate IG Farben) reproduced Lebedev's processes of producing polybutadiene by using sodium as a catalyst. For this, they used the trade name Buna, derived from Bu 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 v ...
, Na for sodium (natrium in Latin, Natrium in German). They discovered that the addition of styrene to the process resulted in better properties, and thus opted for this route. They had invented styrene-butadiene, which was named Buna-S (S for styrene). Although the Goodrich Corporation had successfully developed a process for producing polybutadiene in 1939, the government of the United States opted for the use of Buna-S to develop its synthetic rubber industry after its entry into the World War II, using patents of IG Farben obtained via
Standard Oil Standard Oil Company, Inc., was an American oil production, transportation, refining, and marketing company that operated from 1870 to 1911. At its height, Standard Oil was the largest petroleum company in the world, and its success made its co- ...
. Because of this, there was little industrial production of polybutadiene in America during this time. After the war, the production of synthetic rubber was in decline due to the decrease in demand when natural rubber was available again. However, interest was renewed in the mid-1950s after the discovery of the Ziegler–Natta catalyst. This method proved to be much better for tire manufacturing than the old sodium polybutadiene. The following year, Firestone Tire and Rubber Company was first to produce low ''cis'' polybutadiene using butyllithium as a catalyst. The relatively high production costs were a hindrance to commercial development until 1960 when production on a commercial scale began. Tire manufacturers like
Goodyear Tire and Rubber Company The Goodyear Tire & Rubber Company is an American multinational tire manufacturing company founded in 1898 by Frank Seiberling and based in Akron, Ohio. Goodyear manufactures tires for automobiles, commercial trucks, light trucks, motorcycles, ...
and Goodrich were the first to produce plants for high ''cis'' polybutadiene, this was followed by oil companies like Shell and chemical manufacturers such as Bayer. Initially, with plants built in the United States and France, Firestone enjoyed a monopoly on low ''cis'' polybutadiene, licensing it to plants in Japan and the United Kingdom. In 1965, the Japanese
JSR Corporation JSR may refer to: Jai Shri Raam Computing * Jump to subroutine, an assembly language instruction * Java Specification Request, documents describing proposed additions to the Java platform Research, science & technology * Joint spectral radius, in ...
developed its own low ''cis'' process and began licensing it during the next decade. The 1973 oil crisis marked a halt to the growth of synthetic rubber production; the expansion of existing plants almost ceased for a few years. Since then, the construction of new plants have been mainly focused to industrializing countries in the Far East (such as South Korea, Taiwan, Thailand and China), while Western countries have chosen to increase the capacity of existing plants. In 1987, Bayer started to use neodymium-based catalysts to catalyze polybutadiene. Soon thereafter other manufacturers deployed related technologies such as EniChem (1993) and Petroflex (2002). In the early 2000s, the synthetic rubber industry was once again hit by one its periodic crises. The world's largest producer of polybutadiene, Bayer, went through major restructurings as they were troubled by financial losses; between 2002 and 2005 they closed its cobalt-polybutadiene plants in Sarnia (Canada) and Marl (Germany), transferring their production to neodymium plants in Port Jérôme (France) and Orange (USA). During the same time, the synthetic rubber business was transferred from Bayer to Lanxess, a company founded in 2004 when Bayer spun off its chemicals operations and parts of its polymer activities.


Polymerization of butadiene

1,3-Butadiene is an
organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
that is a simple conjugated
diene In organic chemistry a diene ( ) (diolefin ( ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nomenclature. ...
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
(dienes have two carbon-carbon double bonds). Polybutadiene forms by linking many 1,3-butadiene monomers to make a much longer polymer chain molecule. In terms of the connectivity of the polymer chain, butadiene can polymerize in three different ways, called ''cis'', ''trans'' and ''vinyl''. The cis and trans forms arise by connecting the butadiene molecules end-to-end, so-called 1,4-polymerisation. The properties of the resulting isomeric forms of polybutadiene differ. For example, "high cis"-polybutadiene has a high elasticity and is very popular, whereas the so-called "high ''trans''" is a plastic crystal with few useful applications. The vinyl content of polybutadiene is typically no more than a few percent. In addition to these three kinds of connectivity, polybutadienes differ in terms of their branching and molecular weights. The ''trans'' double bonds formed during polymerization allow the polymer chain to stay rather straight, allowing sections of polymer chains to align to form microcrystalline regions in the material. The ''cis'' double bonds cause a bend in the polymer chain, preventing polymer chains from aligning to form crystalline regions, which results in larger regions of amorphous polymer. It has been found that a substantial percentage of ''cis'' double bond configurations in the polymer will result in a material with flexible elastomer (rubber-like) qualities. In free radical polymerization, both ''cis'' and ''trans'' double bonds will form in percentages that depend on temperature. The
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
s influence the ''cis'' vs ''trans'' ratio.


Types

The catalyst used in the production significantly affects the type of polybutadiene product.


High ''cis'' polybutadiene

This type is characterized by a high proportion of ''cis'' (typically over 92%) and a small proportion of vinyl (less than 4%). It is manufactured using Ziegler–Natta catalysts based on transition metals. Depending on the metal used, the properties vary slightly. Using cobalt gives branched molecules, resulting in a low viscosity material that is easy to use, but its mechanical strength is relatively low. Neodymium gives the most linear structure (and therefore higher mechanical strength) and a higher percentage of 98% ''cis''. Other less-used catalysts include nickel and titanium.


Low ''cis'' polybutadiene

Using an alkyllithium (e.g. butyllithium) as the catalyst produces a polybutadiene called "low ''cis''" which typically contains 36% ''cis'', 59% ''trans'' and 10% vinyl. Despite its high liquid-glass transition, low ''cis'' polybutadiene is used in tire manufacturing and is blended with other tire polymers, also it can be advantageously used as an additive in plastics due to its low contents of gels.


High vinyl polybutadiene

In 1980, researchers from the Japanese company, Zeon, discovered that high-vinyl polybutadiene (over 70%), despite having a high liquid-glass transition, could be advantageously used in combination with high ''cis'' in tires. This material is produced with an alkyllithium catalyst.


High ''trans'' polybutadiene

Polybutadiene can be produced with more than 90% ''trans'' using catalysts similar to those of high ''cis'': neodymium,
lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between l ...
, nickel. This material is a plastic crystal (i.e. not an elastomer) which melts at about 80 °C. It was formerly used for the outer layer of golf balls. Today it is only used industrially, but companies like Ube are investigating other possible applications.


Other


=Metallocene polybutadiene

= The use of metallocene catalysts to polymerize butadiene is being explored by Japanese researchers. The benefits seem to be a higher degree of control both in the distribution of molecular mass and the proportion of cis/trans/vinyl. As of 2006, no manufacturer produces "metallocene polybutadiene" on a commercial basis.


=Copolymers

= 1,3-butadiene is normally
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 ...
ized with other types of monomers such as styrene and
acrylonitrile Acrylonitrile is an organic compound with the formula and the structure . It is a colorless, volatile liquid although commercial samples can be yellow due to impurities. It has a pungent odor of garlic or onions. In terms of its molecula ...
to form rubbers or
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adapta ...
s with various qualities. The most common form is styrene-butadiene copolymer, which is a commodity material for car tires. It is also used in block copolymers and tough thermoplastics such as ABS plastic. This way a copolymer material can be made with good
stiffness Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a ...
,
hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...
, and
toughness In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.repeat unit, the material is sensitive to
ozone cracking Cracks can be formed in many different elastomers by ozone attack, and the characteristic form of attack of vulnerable rubbers is known as ozone cracking. The problem was formerly very common, especially in tires, but is now rarely seen in those ...
.


Production

The annual production of polybutadiene was 2.0 million tons in 2003. This makes it the second most produced synthetic rubber by volume, behind the styrene-butadiene rubber (SBR). The production processes of high ''cis'' polybutadiene and low ''cis'' used to be quite different and were carried out in separate plants. Lately, the trend has changed to use a single plant to produce as many different types of rubber as possible, including, low ''cis'' polybutadiene, high ''cis'' (with neodymium used as a catalyst) and SBR.


Processing

Polybutadiene rubber is seldom used alone, but is instead mixed with other rubbers. Polybutadiene is difficult to band in a two roll mixing mill. Instead, a thin sheet of polybutadiene may be prepared and kept separate. Then, after proper mastication of natural rubber, the polybutadiene rubber may be added to the two roll mixing mill. A similar practice may be adopted, for example, if polybutadiene is to be mixed with Styrene Butadiene Rubber (SBR). *Polybutadiene rubber may be added with Styrene as an impact modifier. High dosages may affect clarity of Styrene. In an internal mixer, natural rubber and/or styrene-butadiene rubber may be placed first, followed by polybutadiene. The plasticity of polybutadiene is not reduced by excessive mastication.


Uses

The annual production of polybutadiene is 2.1 million tons (2000). This makes it the second most produced synthetic rubber by volume, behind styrene-butadiene rubber (SBR).


Tires

Polybutadiene is largely used in various parts of automobile tires; the manufacture of tires consumes about 70% of the world production of polybutadiene, with a majority of it being high ''cis''. The polybutadiene is used primarily in the sidewall of truck tires, this helps to improve fatigue to failure life due to the continuous flexing during run. As a result, tires will not blow out in extreme service conditions. It is also used in the tread portion of giant truck tires to improve the abrasion, i.e. less wearing, and to run the tire comparatively cool, since the internal heat comes out quickly. Both parts are formed by
extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
. Its main competitors in this application are styrene-butadiene rubber (SBR) and natural rubber. Polybutadiene has the advantage compared to SBR in its lower liquid-glass transition temperature, which gives it a high resistance to wear and a low rolling resistance. This gives the tires a long life and low fuel consumption. However, the lower transition temperature also lowers the friction on wet surfaces, which is why polybutadiene almost always is used in combination with any of the other two elastomers. About 1 kg of polybutadiene is used per tire in automobiles, and 3.3 kg in utility vehicles.


Plastics

About 25% of the produced polybutadiene is used to improve the mechanical properties of plastics, in particular of high-impact polystyrene (HIPS) and to a lesser extent acrylonitrile butadiene styrene (ABS). The addition of between 4 and 12% polybutadiene to polystyrene transforms it from a fragile and delicate material to a ductile and resistant one. The quality of the process is more important in the use in plastics than in tires, especially when it comes to color and content of gels which have to be as low as possible. In addition, the products need to meet a list of health requirements due to its use in the food industry.


Golf balls

Most golf balls are made of an elastic core of polybutadiene surrounded by a layer of a harder material. Polybutadiene is preferred to other elastomers due to its high resilience. The core of the balls are formed by compression molding with chemical reactions. First, polybutadiene is mixed with additives, then extruded, pressed using a calender and cut into pieces which are placed in a mold. The mold is subjected to high pressure and high temperature for about 30 minutes, enough time to vulcanize the material. The golf ball production consumes about 20,000 tonnes of polybutadiene per year (1999).


Other uses

* Polybutadiene rubber may be used in the inner tube of hoses for sandblasting, along with natural rubber, to increase resilience. This rubber can also be used in the cover of hoses, mainly pneumatic and water hoses. * Polybutadiene rubber can also be used in railway pads, bridge blocks, etc. * Polybutadiene rubber can be blended with nitrile rubber for easy processing. However large use may affect the oil resistance of nitrile rubber. * Polybutadiene is used in the manufacturing of the high- restitution toy Super Ball. Due to the high resilience property, 100% polybutadiene rubber based vulcanizate is used as crazy balls — i.e. a ball if dropped from 6th floor of a house will rebound up to 5½ to 6th floor (assuming no air resistance). * Polybutadiene is also used as binder in combination with an oxidizer and a fuel in various Solid Rocket Boosters such as Japan's H-IIB launch vehicle, and ESA's Ariane 5; commonly is employed as hydroxyl-terminated polybutadiene (HTPB) or carboxyl-terminated polybutadiene (CTPB).


See also

*
Ozone cracking Cracks can be formed in many different elastomers by ozone attack, and the characteristic form of attack of vulnerable rubbers is known as ozone cracking. The problem was formerly very common, especially in tires, but is now rarely seen in those ...
* Polymer degradation


References

;Bibliography * * *


External links

{{commonscatinline Organic polymers Elastomers Thermoplastics Polymers Russian inventions