Cis 1,4 polybutadiene

The cis-polybutadiene, cis-polyisoprene, and ethylene-propylene rubbers are close duphcates of natural rubber. The newer eth)aene-propylene rubbers (EPR) have excellent resistance to heat and oxidation. 

Ziegler-Natta catalysts currently produce linear polyethylene (non-branched), stereoregular polypropylene, cis-polybutadiene, and other stereoregular polymers. 

Polymerization of butadiene using anionic initiators (alkyllithium) in a nonpolar solvent produces a polymer with a high cis configuration. A high cis-polybutadiene is also obtained when coordination catalysts are used. 

The most spectacular case of products arising from a catalyst invention is that of the stereospecific hydrocarbon polymers made possible by the Ziegler-Natta work on aluminum alkyl/transition metal halide combinations around 1950. Until these catalysts existed, polypropylene, polyiso-prene, and cis-polybutadiene could not be made, and linear polyethylene could not be made cheaply. For each of these products, very large investments were needed in big plants and in market development before they were competitive with the established, big thermoplastics and rubbers. Entrance fees ran into tens of millions of dollars. 

It has been known that 7r-allylnickel halides are catalysts for polymerization of butadiene (50, 51). When the halide is chloride, the polymer formed is cis-polybutadiene when the halide is iodide, the polymer is trans-polybutadiene. Porri and co-workers (50) interpret this effect in terms of the ease of dissociation of the dimeric complex 29 by butadiene. The chloride complex... 

For cls-polyisoprene and cis polybutadiene, the interpretation is based on Ti, NOE and T2 values ( W) although utilization of T2 is complicated because of the possible presence of systematic errors particularly in spectrometers employing superconducting magnets. The interpretation for PE and to a lesser extent PIB is not unique. Several choices of segment length are possible and the parameters listed in Table V are for a minimum length which... 

Fiir die Unterscheidung der cis- und trans-Isomeren bei 1.4-Polymerisation zieht R. R. Hampton 120 b) folgende Schliisselfrequenzen heran 967 cmfiir trans-, 724 cm i fiir cis-Polybutadiene. 

The properties of impact polystyrene can be improved by simultaneous grafting and crosslinking upon rubber. Changing cis-polybutadiene into trans-polybutadiene and eliminating the 1,2-vinyl configuration through radiation are discussed by Parkinson. 

Figure 3. Concentration of olefin groups in irradiated cis-polybutadiene...

Hydrocarbon - An organic chemical compound containing the elements carbon and hydrogen. Aliphatic hydrocarbons are straight chain compounds and aromatic hydrocarbons are based on the cyclic or benzene ring. They may be gaseous, (methane, ethylene, butadiene) liquid (hexane, benzene) or solid (natural rubber, naphthalene, cis-polybutadiene). 

The new absorptions in the spectra of crosslinked rubber are assigned on the basis of 13C solution NMR chemical shifts for a variety of model compounds, such as pentenes and mono-, di- and tri-sulfidic compounds, by using the 13C chemical shift substituent effect. From the calculated values for particular structural units, the experimental spectra of a sulfur vulcanized natural rubber 194,195,106), natural rubber cured by accelerated sulfur vulcanization 197 y-irradiation crosslinked natural rubber198 and peroxide crosslinked natural rubber and cis-polybutadiene 193 1991 are assigned. 

A plot of the effect of ionicities of the catalyst and the structures which are produced and the requirements for the production of cis polybutadiene, cis polyisoprene and cis pentadiene is shown in Fig. 14. Cis and trans poly-1.3-dienes are produced according to the balance of ionicities of the catalyst. 

The anionic nickel acetylacetonate catalyst gives only the cis, cis, trans product. Intermediate catalysts have already been seen to give cis, cis, cis structures which do not terminate but produce cis polybutadiene. This will also be seen later with cobalt iodide. At high temperatures or with strongly cationic systems the cyclic dodecatrienes are isomerized to the most stable trans, trans, trans structure. 

The more cationic halogen containing compounds produced other products. Cobalt bis-allyliodide produced cis-polybutadiene and the even more cationic chromium, produced cyclododecatriene. Only with the more cationic system which introduced trans-structures, was cyclization and reduction of the metal able to intercept the polymerization reaction. Cyclization was not possible in the less cationic cobalt which produces all cis-polybutadiene nor was the hydride transfer possible with the less anionic chromium tris-allyl compound. 

The question immediately raised is would this technique portray an opposite or negative adhesion response if applied to a polymer blended system where no interfacial bonding could be present Such a system would be cis-polybutadiene and high molecular weight polyisobutylene restricted to that portion of the blend system where polyisobutylene is the minor dispersed phase in cis-polybutadiene. A high molecular weight polyisobutylene [L-300 Vistanex (Enjay Chemical Co.)] was compounded with zinc oxide, sulfur, and TMTDS and then dissolved in hexane. cis-Polybutadiene (Phillips Chemical Co.) was also mixed with... 

The system Cl-butyl-cis-polybutadiene has been studied in some detail because it was suitable for the developed differential swelling technique and because this system of blends vulcanized with zinc oxide, sulfur, and thiuram disulfide first revealed the presence of interfacial bonds. This curative system has the feature of a flat cure —i.e.y the two homophases are vulcanized rapidly, and the crosslinked density does not increase radically as vulcanization time is prolonged. This is observed in Table IV by swelling and extractable levels of a series of crosslinked networks cured at increasing times and swollen in a common solvent, cyclohexane. 

Table IV. Swelling Volumes and Extractable Contents of Networks of Cl—Butyl and cis-Polybutadiene-Vulcanized at 300°F—Sulfur, Zinc Oxide, TMTDS...

Figure 11. Compounding variations in blended elastomer phases (Cl-butyl-cis-polybutadiene). A thiazole in cis-PB phase impairs adhesion.

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