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Suspension Polymerization of Styrene Using Zinc Oxide as a Suspension Agent



Author(s)

Rochmadi and Edy Widjaja

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DOI:10.17265/2161-6221/2011.09.002

Department of Chemical Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55284, Indonesia

The advantage of suspension polymerization is that the polymer product can be separated easily from the mixture of reaction product, in the form of small spherical polymer solid. This method is commonly employed in the production of expanded polystyrene. This research has investigated the reaction rate of suspension polymerization of styrene, along with the product characteristics. Classical model on chain polymerization was proposed, to determine the rate of reaction. The experiment was conducted in a three neck flask provided with a stirrer and water bath. The reaction was run at temperature 60 °C-90 °C and pH of 10. Sample was taken regularly from the reaction mixture at certain time, and the remaining styrene monomer in the sample was determined by gravimetric method (i.e. vacuumed vaporization). In the end of experiment, the polymer product (in the form of small sphere) was separated from the suspension mixture, dried and measured its diameter. The molecular weight of polystyrene product was measured by capillary viscometer. The results showed that the proposed reaction rate model fitted well to the experimental data, with its relative error being around 2.38%-10.9%, hence it was good enough to describe suspension polymerization process. The overall polymerization reaction rate constants was around 2.34-45.1 (L/mol)^0.5, which depends on mainly the reaction temperature. The initiator decomposition rate constant was around 0.0051-0.0091 min^-1. Suspension agent concentration did not influence the styrene conversion. The diameter of polystyrene particle was around 0.1-1 mm, which was influenced by reaction temperature and suspension agent concentration. Viscosity average molecular weight of polystyrene products was between 100,000 to 670,000.

Suspension polymerization, styrene, zinc oxide, suspension agent.