Butadiene‐1,3 and acrylonitrile were copolymerized by alkylaluminum halides alone or, more effectively, by the alkylaluminum halide/vanadium compound systems, into an alternating copolymer in which the butadiene units are linked predominantly in the trans‐1,4 configuration. The efficiency of the aluminum components in the latter catalyst systems appear to decrease in the following order: AlEtCl2 > Al2Et3Cl3 ≫ AlEt2Cl(≫AlCl3). The alkylaluminum halides could also be used effectually in the form of the complex with acrylonitrile. The catalytic activity was markedly affected by the order of mixing of the catalyst components and the monomers. Effective catalysts could be prepared only when the catalyst components were mixed in the presence of acrylonitrile. The catalyst activity was also found to depend upon the Al/V ratio, reaching its maximum when the ratio was about 20 in the AlEtCl2·AN/VO(Ot‐Bu)3 system. Other combinations of conjugated diene with conjugated polar vinyl monomer were similarly copolymerized by these catalysts. It was found that different feed ratios between the diene and the vinyl monomer which were varied over a wide range always resulted in the formation of a 1:1 copolymer. The butadiene‐acrylonitrile copolymer thus formed gave an NMR spectrum in which there was only one peak assignable to the methylene protons (7.72 τ) of the butadiene unit. On the basis of these findings, it may be suggested that alternating copolymerization prevails in the polymerization systems here investigated.
Finite element methods are applied for multilayer elastomeric bearings under large deformation. The method is capable of handling nonlinear elasticity and incompressibility of rubber-like materials. The strain energy density function which determines elastic properties of the materials is obtained empirically through strip biaxial testing. The computation using the strain energy density function is conducted to analyze the stress and strain distribution and the performance characteristics of multilayer elastomeric bearings, which is in good agreement with the results of actual experiments.
The mechanism of the alternating copolymerization of butadiene with acrylonitrile catalyzed by EtAICl2 and VOCla was investigated experimentally using various concentrations of catalysts at varying temperatures. A step-growth polymerization was postulated from the characteristic feature of polymerization that the molecular weight of a resultant polymer increases in the course of polymerization. A linear correlation was found to exist between the ratio of the yield to the degree of polymerization and the yield, which suggests that polymerization proceeds with rapid initiation and chain transfer reactions. The overall rate of polymerization was found to be expressed as a function of (EtAIClz) 3/ 2 x (VOCla) 1/ 2 and the concentration of the active species as a function of (EtA1Clz) 1/ 2 x (V0Cla) 1 1 2 • These facts suggest that the active species is generated from the dissociation of the EtAlClz-VOCla complex through a redox mechanism and the propagation reaction takes place between the polymer radical and a complexed monomer of butadiene-acrylonitrile-EtAlCb. Vanadium compound acts not only as a generator of the active species but also as a useful cocatalyst capable of regenerating the complexing agent for the monomer and preventing the polymer from gel formation.
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