ACTIVATION OF MAGNESIUM-CHLORIDE BY DRY MILLING

Extensive dry ball milling (up to 200 h in a vibratory mill) of the layer-lattice type MgCl2 structure (used as olefin polymerization support) results in a moderate reduction in the mean particle size and a more pronounced decrease in crystallite size in directions parallel and transverse to the hexagonal crystal axis. The relative reductions in crystallite size are understood on the basis of sliding of the Cl-Mg-Cl double layers by the action of shear. The effect is accompanied by a change from cubic or hexagonal close packed layer structures to arrangements with lattice disorder. The effect can be reversed completely by annealing above about 250-degrees-C.