| Abstract: | Three different types of high activity magnesium chloride catalysts were prepared and used for propylene polymerization both in the absence and in the presence of external donors. The rates of polymerization were studied as functions of polymerization time, and the effects of methyl paratoluate and diphenyldimethoxysilane as external donors were investigated. Active centre concentrations (C*) were determined using tritiated methanol quenching and 14CO radio-labelling in order to assess their applicability. A relatively good agreement between values of C* evaluated by the use of these two methods was obtained. The morphologies of the supports, catalysts and polymers produced were studied using scanning electron microscopy. A model involving expanding microreactors is proposed for polymer growth. |
