Lithium-catalyzed solution polymers

The relative levels of each of the three isomers in a polymer such as BR can have a dramatic effect on the material s performance. For example, lithium-catalyzed solution polymers, with approximately 36% cfj content, tend to process easily, whereas high-cw Ti and Ni polymers (92% cis) are more difficult to process at factory processing temperatures but show better abrasion resistance. Y igh-trans BR (93% trans) tends to be a tough, crystalline material at room temperature. High vinyl-butadiene BR polymers in tire treads tend to show good wet skid and wet traction performance (Mezynski and Rodgers, 1993 Simpson, 1978 Nordsiek, 1985 Rodgers et al., 2004). 

The microstructure of polybutadiene can have a significant effect on the elastomer s performance. For example, lithium-catalyzed solution polymers, containing approximately 36% cts-butadiene, tend to process easily in tire manufacturing plants whereas high cis-polymers produced with titanium or nickel catalysts (cis-content >90%) tend to be more difficult to process in tire factories (Table 4.2). For example, gage control of extruded components may be more difficult though such compounded polymers have been reported to show better abrasion resistance when compared to the low cis-polymer [2]. 

Styrene butadiene n. A group of thermo plastic elastomers. They are linear co-polymers of styrene and butadiene, produced by lithium catalyzed solution polymerization, with a sandwich molecular structure containing a long Polybutadiene center surrounded by shorter polystyrene ends. A co-polymer of styrene and butadiene made by emulsion polymerization for use in latex paints. 

Addition of a catalyst modifier during the preparation of solution-polymerized, lithium-catalyzed BR results in an increase in the vinyl-1,2-butadiene level in the polymer and causes an increase in Fg. There is a corresponding drop in abrasion resistance and an increase in wet traction. 

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