Kaminsky

EinaHy, in 1976, Kaminsky and Sinn in Germany discovered a new family of catalysts for ethylene polymerization. These catalysts (ie, Kaminsky catalysts) contain two components a metallocene complex, usually a zkconocene, and an organoaluminum compound, methylaluminoxane (8,9). These catalysts and thek various later modifications enable the synthesis of ethylene copolymers with a high degree of branching uniformity. Formally classified as MDPE, LLDPE, or VLDPE, the resins thus produced have a number of properties that set them apart from common PE resins in terms of performance... 

LLDPE resias are produced ia iadustry with three classes of catalysts (11—14) titanium-based catalysts (Ziegler), metallocene-based catalysts (Kaminsky and Dow), and chromium oxide-based catalysts (Phillips). 

Metallocene Catalysts. Three types of metallocene catalysts are presentiy used ia industry Kaminsky, combination, and Dow catalysts. 

Most Kaminsky catalysts contain only one type of active center. They produce ethylene—a-olefin copolymers with uniform compositional distributions and quite narrow MWDs which, at their limit, can be characterized by M.Jratios of about 2.0 and MFR of about 15. These features of the catalysts determine their first appHcations in the specialty resin area, to be used in the synthesis of either uniformly branched VLDPE resins or completely amorphous PE plastomers. Kaminsky catalysts have been gradually replacing Ziegler catalysts in the manufacture of certain commodity LLDPE products. They also faciUtate the copolymerization of ethylene with cycHc dienes such as cyclopentene and norhornene (33,34). These copolymers are compositionaHy uniform and can be used as LLDPE resins with special properties. Ethylene—norhornene copolymers are resistant to chemicals and heat, have high glass transitions, and very high transparency which makes them suitable for polymer optical fibers (34). 

Fig. 3. Metallocene catalyst systems for LLDPE synthesis (a) Kaminsky catalyst (b) cationic catalyst and (c) Dow catalyst.

T. DaH-Occo, U. Zucchini, and 1. Cufftani, in W. Kaminsky and H. Sinn, eds.. Transition Metals and Organometallics as Catalystsfor Olefin Polymerisation, Springer-Vedag, Berlin, 1988, p. 209. 

Metallocene Catalysts. Polymerization of cycloolefins with Kaminsky catalysts (combinations of metallocenes and methylaluminoxane) produces polymers with a completely different stmcture. The reactions proceeds via the double-bond opening in cycloolefins and the formation of C—C bonds between adjacent rings (31,32). If the metallocene complexes contain bridged and substituted cyclopentadienyl rings, such as ethylene(hisindenyl)zirconium dichloride, the polymers are stereoregular and have the i j -diisotactic stmcture. 

M. S. Kaminsky and J. M. Lafferty, Dictionay of Terms for Vacuum Science and Technology, American Vacuum Society, Thorofare, N.J., 1980, pp. 70—71. 

W. Kaminski and T. Paryjczak, Eesy. ISSauk.-Politech. Tody. Chem. 41, 237 (1987). 

G Kaminski, EM Duffy, T Matsui, WL Jorgensen. J Phys Chem 98 13077-13082, 1994. WL Jorgensen, J Tirado-Rives. J Am Chem Soc 110 1657-1666, 1988. 

Other researchers have substantially advanced the state of the art of fracture mechanics applied to composite materials. Tetelman [6-15] and Corten [6-16] discuss fracture mechanics from the point of view of micromechanics. Sih and Chen [6-17] treat the mixed-mode fracture problem for noncollinear crack propagation. Waddoups, Eisenmann, and Kaminski [6-18] and Konish, Swedlow, and Cruse [6-19] extend the concepts of fracture mechanics to laminates. Impact resistance of unidirectional composites is discussed by Chamis, Hanson, and Serafini [6-20]. They use strain energy and fracture strength concepts along with micromechanics to assess impact resistance in longitudinal, transverse, and shear modes. 

J. R. Eisenmann, B. E. Kaminski, D. L. Reed, and D, J. Wilkins, Toward Reliable Composites An Examination of Design Methodology, Journal of Composite Materials, July 1972, pp. 143-169. 

However, we also need to discuss how the attractive interactions between species can be included in the theory of partly quenched systems. These interactions comprise an intrinsic feature of realistic models for partially quenched fluid systems. In particular, the model for adsorption of methane in xerosilica gel of Kaminsky and Monson [41] is characterized by very strong attraction between matrix obstacles and fluid species. Besides, the fluid particles attract each other via the Lennard-Lones potential. Both types of attraction (the fluid-matrix and fluid-fluid) must be included to gain profound insight into the phase transitions in partly quenched media. The approach of Ford and Glandt to obtain the chemical potential utilizing... 

Adsorption of hard sphere fluid mixtures in disordered hard sphere matrices has not been studied profoundly and the accuracy of the ROZ-type theory in the description of the structure and thermodynamics of simple mixtures is difficult to discuss. Adsorption of mixtures consisting of argon with ethane and methane in a matrix mimicking silica xerogel has been simulated by Kaminsky and Monson [42,43] in the framework of the Lennard-Jones model. A comparison with experimentally measured properties has also been performed. However, we are not aware of similar studies for simpler hard sphere mixtures, but the work from our laboratory has focused on a two-dimensional partly quenched model of hard discs [44]. That makes it impossible to judge the accuracy of theoretical approaches even for simple binary mixtures in disordered microporous media. 

---