Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

  • Beatriz Paredes
  • Rafael van Grieken
  • Alicia Carrero
  • Ester Lopez-Moya
Original Paper


Polypropylene with wider or bimodal molecular weight distribution is required for numerous applications since low molecular weight chains improve processability and high molecular weight fraction is required to get good mechanical properties. There are several routes to achieve a bimodal resin but the use of a binary catalytic system seems to be the most attractive, particularly with metallocenes combination. From a previous work two metallocenes were selected because they lead to polypropylenes with average molecular weights that differ in one order of magnitude. Two types of binary systems have been investigated, hybrid catalysts (two metallocenes loaded on the same support) and physical mixtures (two independent supported metallocenes that are introduced to the reactor and start the polymerization together), using different ratios, i.e., 25–75, 50–50, 75–25, at three reaction temperatures, i.e., 30, 50 and 70 °C. Most of the binary catalytic systems lead to bimodal molecular weight distributions. Polypropylenes produced by mixed catalysts are greatly influenced by the most active catalyst, while in PP coming from hybrid catalysts, as there is a strong interaction between both metallocenes, each one contributes according to its presence in the hybrid catalyst. Therefore, properties of obtained bimodal polypropylenes are quite influenced by the ratio between both metallocenes.


Metallocene catalysts (poly)propylene (PP) Molecular weight distribution Isotactic Multicomponent or binary catalysts 



Financial support from “Ministerio de Educación y Ciencia” (Spain, Project number: CTQ2008-04601) is kindly acknowledged.


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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • Beatriz Paredes
    • 1
  • Rafael van Grieken
    • 1
  • Alicia Carrero
    • 2
  • Ester Lopez-Moya
    • 1
  1. 1.Department of Chemical and Environmental Technology, ESCETUniversidad Rey Juan CarlosMadridSpain
  2. 2.Department of Chemical and Energy Technology, ESCETUniversidad Rey Juan CarlosMadridSpain

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