Synthesis of uniform rod-like polymer particles via propylene polymerization using metallocene catalysts supported on Stober silica

Monodispersed silica particles were synthesized via Stober method and were used to support Me₂Si(Ind)₂ZrCl₂)/MAO for studying the effects of silica size and MAO concentration on propylene polymerization activity, polypropylene particle shape / size and polymer properties. 5nm catalyst exhibited significantly better polymerization activity and produced much more uniform polymer particles than 700nm catalyst did, which was ascribed to their differences in local mass and heat transfer coefficients. With the increase of external MAO concentration, polymer yield, particle size, molecular weight and melting point increased but molecular weight distribution decreased. Uniform rod-shaped PP particles were fabricated at an intermediate MAO concentration, which packed with numerous polymer nanofibrils and had a smooth exterior surface.