High-vinyl polybutadienes

Polybutadiene. The many forms that can result from the polymerisation of butadiene, depending on the catalysts used, include high cis, medium cis, low cis, and high vinyl polybutadiene (PBD) (see Elastomers, synthetic-polybutadiene). 

Several reports iu the Hterature describe the preparation and characterization of low, medium, and high vinyl polybutadienes (55—69). Each of these references used polar modifiers including chelating diamines, oxygenated ether compounds, acetals, ketals, and compounds of similar stmctures (56—64). 

In the mid-1970s there was a short period during which styrene was in very short supply. This led to the development of what were known as high-vinyl polybutadienes which contained pendent vinyl groups as a result of 1,2-polymer-isation mechanisms. These rubbers had properties similar to those of SBR and could replace the latter should it become economically desirable. 

Figure 1. Stress relaxation curves for three different extension ratios. Uncross-linked high-vinyl polybutadiene with a weight average molecular weight of 2 million and a reference temperature of 283 K. G is the apparent rubber elasticity modulus calculated from classical affine theory. (Solid line is data from Ref. 1).

The effect of cross-linking in the unstrained state is shown in Figure 4 for a high-vinyl polybutadiene with a molecular weight of... 

Figure 10. Electron micrographs of (a) a 50/50 blend of IR and high-cis polybutadiene and (b) a 50/50 blend of medium-cis poly butadiene and high-vinyl polybutadiene. See Table 111 for details of diene microstructures.

Takeuchi, Y. Yoshimura, Y. Ohshima, N. Sakakibara, M. High Vinyl Polybutadiene or Styrene-Butadiene Copolymer. U.S. Patent 4,397,994, Aug 9, 1983 Japan Synthetic Rubber. 

These properties determine how carbon black will be distributed within the blend. These properties are not those of the filler but are the essential properties of the matrix. The matrix thus has strong influence on particle distribution. SEM studies showed that high vinyl polybutadiene and styrene-butadiene copolymers had morphologically identical carbon black distribution. However, their mechanical properties were very different. NMR analysis indicated that the difference in mechanical behavior is related to the interaction and more precisely to the molecular motions in rubbery matrix. 

Sulfur, or the so-called coagents (Loan, 1963 Lenas, 1964), can be used to suppress scission. Examples of coagents are m-phenylenebismaleimide, high-1,2 (high-vinyl)polybutadiene, triallyl cyanurate, diallyl phthalate, and ethylene diacrylate. Their mechanism of action may be as follows ... 

Peng, Z. L., Olson, B. G., Srithawatpong, R., McGervey, J. D., Jamieson, A. M., Ishida, H., Maier, T. M., and Halasa, A. R, Study of free volume in high vinyl-polybutadiene/cis-polyisoprene blends by positron annihilation lifetime spectroscopy, J. Polym. Sci. Polym. Phys., 36, 861-871 (1998). 

The compound n-butyllithium was the initiator and cyclohexane the solvent for high-vinyl polybutadienes produced from anionic polymerisation. Complexing... 

No.2,1991,p.338-42 RAMAN SPECTROSCOPIC CHARACTERISATION OF HIGH-VINYL POLYBUTADIENES PRODUCED FROM ANIONIC POLYMERISATION Poshyachinda S Edwards H G M Johnson A F BRADFORD,UNIVERSITY... 

Networks were prepared by cross-linking strips of three different samples of high-vinyl polybutadiene with the following contents of 1,2 microstructure A, 95% B,... 

Three high-vinyl polybutadienes were used, identified as A, B, and C in previous publications, generously provided by Dr. G. Kraus of the Phillips Petroleum Company and... 

D. F. Lohr, Jr. and W. Kang, Blend of High-Vinyl Polybutadiene and Hydroformylated High-Vinyl Polybutadiene, U.S. Pat. 3,928,282 (1975). Blended elastomers simultaneously vulcanized and grafted. 

In contrast to the inherent linearity exhibited by immodified low vinyl polybutadiene polymerized at moderate temperature, medium to high vinyl polybutadiene produced in continuous systems have the tendency to be highly branched. The common use of alkali metal alkoxides with or without additional polar modifiers to increase the vinyl content results in a superbasic system with a high tendency to metallate the polymer chain (137-141). The metallated site can reinitiate in the presence of continuously fed monomer and produce random... 

Medium and High Vinyl Polybutadiene. Many tire performance properties are closely related to the glass-transition temperature of the polymer system used (324,325,346). As the glass-transition temperature is increased, wet and dry traction is increased, but abrasion resistance is compromised (347). Again, hysteretic properties are more a ftmetion of macrostructure than glass-transition temperature. Figure 4 depicts the trends in tire performance properties as a function of polybutadiene vinyl content (271). 

Amorphous high vinyl polybutadienes (>70% vinyl) have glass-transition temperatures higher than -40°C (349). These materials are t5 ically made with lithium initiators combined with a muted alkali metal alkoxide and/or polar modifier system. As a result, commercial high vinyl polybutadienes are t5 ically quite branched but display excellent traction properties. These materials are most often used in silica-filled tire applications. 

The properties of the end product also depend on the structure of the initial polymer. Thus high vinyl polybutadienes which will have ethyl side groups after hydrogenation cannot crystallize and so remain rubbery. As the vinyl content decreases so the hydrogenated product becomes more like low density polyethylene whilst linear... 

Noguchi, K., Yoshioka, A., Komuro, K. and Ueda, A., Structure and properties of newly developed chemically modified high vinyl polybutadiene and solution polymerized styrene-butadiene rubbers , ACS Rubber Division 129th Meeting May, 1986, Paper No. 36. 

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