This article reports the results of a study comparing commercially available high-cis polybutadiene rubbers (BRs) proceeding from different production technologies and bearing distinct structural characteristics. The microstructure of these polymers was characterized by Fourier transform infrared spectroscopy; molecular weight and polydispersity values were characterized by size exclusion chromatography (SEC). The degree of branching was characterized by SEC and dynamic mechanical rheological testing (RPA 2000). Glass-transition temperature was characterized by differential scanning calorimetry, and rheological properties were characterized with an oscillating rheometer rubber process analyzer (RPA 2000). Tire tread formulations were prepared with carbon black HAF N-339 as a reinforcement filler, and we compared the mechanical properties and performance of the different elastomer compositions. The compositions were characterized by their rheological properties, tensile resistance, resistance to abrasion, resistance to tearing, permanent deformation, resilience, and fatigue properties. The tested compositions obtained from BRs with distinct structural characteristics showed different performances. Neodymium-salt-based catalysts produced BRs with higher cis-1,4 levels and higher linearities. These polymer compositions also showed higher performances in abrasion resistance, fatigue resistance, and resilience tests.

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This article is regarding the polymerization of 1,3‐butadiene with a neodymium catalyst activated by diisobutylaluminum‐hydride and diethylaluminum chloride (DEAC). The effects of the polymerization conditions (ratio between DEAC and neodymium molar concentrations, polymerization temperature, catalyst concentration, and butadiene concentration) on the polymer yield and molecular weight distribution (MWD) of polybutadiene (PB) samples were evaluated. It is shown that the DEAC/Nd ratio and the polymerization temperature are the reaction variables that influence the MWD and the catalyst performance most significantly. PBs with broad and sometimes bimodal MWD were produced at the analyzed reaction conditions. For this reason, the MWD of the obtained polymer materials was deconvoluted with the help of the Flory most probable distribution, indicating that three or more catalyst sites are required to explain the final MWD of the polymer samples. Finally, it was observed that the analyzed neodymium catalyst is able to produce branched PBs at mild reaction conditions and that the branching frequency depends on the polymerization conditions, which may be useful for development of operation policies at plant site and production of materials with improved performances. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Resumo: Os catalisadores lantanídicos são muito eficientes na polimerização estereoespecífica de dienos, principalmente aqueles à base de neodímio. Neste trabalho será apresentado o estudo da polimerização do 2-metil, 1,3-butadieno com catalisadores à base de neodímio, utilizados comercialmente na polimerização do 1,3-butadieno. Foi estudado o efeito da temperatura, do tipo de alquilalumínio e da concentração de catalisador. As reações foram realizadas em reator de aço inox sob atmosfera inerte, usando como solvente o hexano e uma concentração de 2-metil, 1,3-butadieno de 12%. Foram obtidos polímeros com massas molares na faixa de 1,0 a 1,5 × 105 e teor de unidades repetitivas cis em torno de 97%. Palavras-chave: Poli-1,4-cis-isopreno, isopreno, neodímio, catalisadores ziegler-Natta. Polymerization of 2-methyl, 1,3-butadiene via Lanthanides Catalysts -Influence from the Type of Alkylaluminum, Concentration and Reaction Temperature and Catalyst Abstract:The rare earth metals catalysts are very efficient in stereospecific polymerization of dienes, especially those of neodymium. This paper reports on the polymerization of 2-methyl, 1,3-butadiene with catalysts of neodymium, used commercially in polymerization of 1,3-butadiene. Effects were studied from the temperature, type of alkylaluminum, and from the concentration of catalyst. The reactions were carried out in a stainless steel reactor under an inert atmosphere, using hexane as the solvent and a concentration of 12% of 2-methyl, 1,3-butadiene. Polymers were obtained with molecular weight from 1.0 to 1.5 × 105, with ca. 97% of cis repeating units.

Recebido em 18/10/95; aceito em 16/8/96 SYNTHESIS OF ZIEGLER-NATTA CATALYSTS: SOME ROUTES AND THEIR DIFFICULTIES. The Ziegler-Natta catalyst and the polymerization thereof are systems which require careful handling and special treatment of chemicals. In spite of the use of inert atmosphere and dry chemicals, some Ziegler-Natta systems may present low activities or even may deactivate because of unsuitable handling. Some features of the TiCl 3 synthesis and its characterization when related to the presence of impurities are described. Evidences of poor handling of chemicals and/or laboratory devices while in synthesis of the catalyst are emphasized. The problems arising from butadiene polymerization and some relevant details in propylene polymerization are also presented with teaching objectives.