• In recent years, with the rapid development of tire, automobile and rubber products industry, the output of synthetic rubber has become one of the indicators to measure the national economic development.
• Cis-1,4-polybutadiene rubber,with abbreviation BR, has ranked the second largest consumption of synthetic rubber just behind styrene butadiene rubber(SBR) since 1960s. For the past few years, the consumption of BR has shown a steady increase continously from 3343 kt in 2015 to 3745 kt in 2020, while it is estimated that the world’s total output will increase at an average annual rate of about 2.6% from 2021 to 2024, and the consumption will reach about 4250 kt in 2024.【1】
•  The consumption structure globally in 2020 is as follows: 71.5 % of the total consumption of tyres and their products, 13.0% of the total consumption of HIPS and ABS resins, while other applications (including special adhesives for rocket thrusters, golf ball cores and non-tyre rubber products, as well as other specialized sealants and waterproofing membranes and specialized adhesives) account for about 15.5%.【2】
• The development of highway results in requirements for high performance tire to meridian, flat, tubutless. Meanwhile, the appealed development direction of green tire indicates that raw material should not only meet the requirements of tire manufacturing technology, but also needs of high-speed, safety, energy saving and environmental protection.
• At present, only BR can supply the various demands. Therefore, it is an inevitable trend for the tire manufacturing industry to use BR instead of traditional butadiene rubber in the production of high performance tires. In addition, the implementation of tire labeling law will further enhance the production of green high-performance tires, and it also provides a good opportunity and space for BR progress【3】.

The molecular structure of cis-1,4-polybutadiene rubber has good regularity, no side group, very flexible molecular chain and narrow molecular weight distribution, so it has good elasticity.

                                                        Figure 1. Structural formula of polybutene and Cis-1,4-butadiene

BR consists of a large amount of soft long molecular chains in a haphazardly organized manner or the cross-link network, difficult to be converted into a machinable plastic state. 

• At present, BR has the best elasticity among all kinds of rubber; besides, the production loss is small, the dynamic heat generation is low, and the bending resistance is excellent. The glass transition temperature is - 105 ℃. It has several cold resistance which is the best one in general rubber. 
• Its high elasticity and low temperature resistance ( glass transition temperature: – 105℃) give rise to its excellent wear resistance. Besides, the hysteresis loss is small and the heat generation performance is low.
• According to its good flexure resistance and flexibility, BR is mainly used in the production of automobile tire for large truck by combination of polybutadiene and natural rubber. The combination promotes the relatively low hysteresis characteristics of tread rubber, so as to promote the reduction of heat accumulation in the tread during tire use.  
• It also correspondingly increases the thermal durability of tread, thus predicts the beneficial reduction of tire rolling resistance to improve the fuel economy of related vehicles. BR achieves the increase of wear resistance without sacrificing other physical properties of the tread of the composition.
• Because of its excellent high elasticity, cold resistance and wear resistance, BR is also used in many consumer products such as electrical products, sporting goods; some selective industrial products such as conveyor belts, hoses, and washers. Cushioning materials and rubber shoes, tapes, and sponge glues also use it in some aspects.【4】The figure 2 shows various applications of BR.                                        
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                                                                                 Figure 2.Various applications 

• The industrial production of cis--polybutadiene rubber adopts the method of solution polymerization. The raw materials mainly include monomer butadiene and solvent, commonly used solvent aliphatic hydrocarbon, alicyclic hydrocarbon, aromatic hydrocarbon and mixed hydrocarbon. The auxiliary raw materials include catalyst, antioxidant and dispersant.
• The main catalysts can be divided into four types: nickel catalyst, titanium catalyst, cobalt catalyst and rare earth catalyst.【5】
• Nickel based catalysts are composed of nickel salts of organic acids, inorganic and organometallic compounds containing fluorine, and trace amounts of water. The content of cis-1,4-configuration in the prepared polybutadiene rubber is as high as 96%. The equivalent period of cis-1,4-polybutadiene is longer, which is 0.86nm. The carbon carbon single bond in the molecule is easier to rotate, especially the single bond beside the double bond is easier to rotate under the influence of the double bond. The chain is flexible. In general, the molecule is curly and has good resilience.
• Titanium catalyst is composed of titanium compounds, aluminum compounds and their halides. Alr3-tii4, alr3-ticl4-i2 and alet2i-ticl4 are commonly used.
• Cobalt based catalysts are mainly cobalt compounds, such as cobalt chloride, oxide, organic acid salt and pyridine complex, which have strong orientation. Usually, high cis-1,4-polybutadiene with cis-1,4-configuration content of 96-98% can be obtained.
• Rare earth catalyst is a kind of catalyst with rare earth compound as main catalyst. The common catalytic systems are: Nd (versa) 3 / Al (i-Bu) 2H / t-bucl, Nd (versa) 3 / Al (i-Bu) 2H / alet3cl3 and Nd (naph) 3-alh (i-Bu) 2-Al (i-Bu) 2Cl.【6】