Bimodal Poly(propylene) through Binary Metallocene Catalytic Systems as an Alternative to Melt Blending

Abstract

AbstractSummary: Propylene was polymerized by three homogenous metallocene catalytic systems: rac‐Me2Si (Ind)2ZrCl2 (CAT‐1), rac‐Et(Ind)2ZrCl2 (CAT‐2) and rac‐Me2Si(2‐Me‐benzoind)2ZrCl22ZrCl2 (CAT‐3) at 50 °C. In function of the molecular‐average weight results of poly(propylene)s obtained, rac‐Et(Ind)2ZrCl2 (CAT‐2) and rac‐Me2Si(2‐Me‐benzoind)2ZrCl2 (CAT‐3) were combined in different proportions (wt %/wt %) of (CAT‐2/CAT‐3) for obtaining a new poly(propylene) with a bimodal molecular weight distribution consisting in clearly separated low and high molecular weight polymer fractions with a difference between them of an order of magnitude. The polymers obtained were compared with those coming from melt mixing of two poly(propylene)s with different molecular weights in an extruder. Both methods allow obtaining bimodal poly(propylene)s, but polymer melt blending shows partial miscibility effects and less crystallinity while binary catalytic systems have several advantages such as lower costs and easier to process that can be controlled to tailor properties together with intimate mixing of high and low molecular weight components.