435084 High Molecular Weight Polypropylene with Me2Si(Ind)2HfCl2/MAO Catalyst System: Kinetics & Effect of Reaction Conditions

Monday, November 9, 2015: 5:00 PM
251B (Salt Palace Convention Center)
Nikhil Prakash, Chemical Engineering Department, Sant Longowal Institute of Engineering & Technology (SLIET), Sangrur (Punjab), India, Sushil Kumar, Chemical Engineering Department, Motilal Nehru National institute of Technology, Allahabad, India and Arvind Kumar Sharma, Chemical Engineering Department, Birla Institute of Technology and Science (BITS), Pilani (Rajsthan), India

Polypropylene is produced by polymerizing propylene with appropriate catalysts. Polypropylene has demonstrated certain advantages in superior strength, stiffness and high temperature capability. Polypropylene has been profitably functional to the forming of fibers due to its good specific strength and is one of the lightest plastics available with a density of 0.905 g/cm3. Polypropylene is used in aerospace and automotive applications, bags, batteries, bottles, coating, computer components and data storage, microwave cookware, cosmetics, eyeglasses, films, fibers, fuel tanks, insulation, medical applications, membrane, food/medical/pharmaceutical packaging, solar panels, tapes, tableware/disposables, sealants etc. [1]

Metallocene catalyzed propylene polymerization has recently attracted research interest since these catalysts allow the production of tailored macromolecules with properties those can be accurately designed. A broad spectrum of properties and applications of the polypropylene can be attained with metallocenes due to their single types of sites.

Metallocene catalyst system refers to the combination of bis(cyclopentadienyl)metal complexes of Group 4 (IVB) [especially zirconium, titanium and hafnium], or cyclopentadienyl-substituted derivatives, and a cocatalyst, typically methylalumoxane (MAO). The number of known metallocene complexes is very large. Various types of metallocenes are generally categorized as nonstereorigid, nonstereorigid ring substituted, stereorigid, cationic and supported metallocenes. [2]

Hafnocenes are known to produce higher molecular weight polypropylene when compared with corresponding Zirconocenes. The complexes with dimethylsilane bridge produce polypropylene with higher molecular weight, stereoregularity and higher melting temperature. [3] In this work, Me2Si(Ind)2HfCl2/MAO catalyst system is studied for polymerization of propylene. A mathematical kinetic model for solution phase polymerization is developed and specific rate constants are determined at 40 °C and 80 °C. A remediated version of differential evolution approach of optimization is proposed and used to solve parameter estimation problem. Developed model consist of a set of coupled, nonlinear and stiff ordinary differential equations, which are solved with MATLAB™ 7.0.1 software. [4]

Developed model is able to captivate vitally essential polymer properties. Molecular weight distribution and fractions of differently terminated chains in polymer are determined.

Effects of polymerization temperature, cocatalyst to catalyst molar ratio, propylene pressure, and catalyst concentration upon rate of polymerization, molecular weight distribution and tacticity are investigated.



  1. http://www.icis.com/Articles/2012/03/26/9544287/global-polymers-to-face-heightened-competition.html on 27th Dec, 2012.
  2. Gupta, V. K., Satish S., Bhardwaj, I. S. (1994). Metallocene complexes of group 4 elements in the polymerization of monoolefins. Journal of Macromolecular Science, Part C, 34, 439-514.
  3. Marques, M. F. V., Poloponsky M., Chaves, É. G. (2002). Comparative study of propylene polymerization with different metallocene catalysts using a statistic experimental planning model. Polímeros: Ciência e Tecnologia, 12 (1), 48-59.
  4. MATLAB version 7.0.1, computer software, The MathWorks, Inc., Natick, Massachusetts 2004.

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See more of this Session: Polymer Reaction Engineering
See more of this Group/Topical: Materials Engineering and Sciences Division