| Přispěvatelé: |
ARJUNAN P., MCGRATH J. E., HANLON T. L., Chadwick, J. C., Morini, G, Balbontin, G, Busico, V, Talarico, Giovanni, Sudmeijer, O. |
| Popis: |
Studies on the effects of hydrogen, monomer concentration and temperature in propene polymerization using high-activity MgCl2-supported catalysts have revealed that the effects of the catalyst on polymer yield, isotacticity and molecular weight are interrelated and dependent on both regio- and stereoselectivity. The high hydrogen sensitivity of catalysts containing a diether donor is mainly due to chain transfer following the occasional regioirregular (2,1-) monomer insertion. The probability of regio- and stereoirregular insertion decreases with monomer concentration, indicating the presence of nonsymmetric active centres. The stereoregularity of the isotactic polymer also increases with polymerization temperature, indicating a greater relative increase in productivity for highly isospecific as opposed to moderately isospecific centres. |
