Effective Parameters on Reaction Kinetics and Particle Size in the Suspension Polymerization of Styrene in the Presence of Graphite

suspension polymerization of styrene in the presence of graphite was carried out. The polymerization reaction kinetics was investigated to gain better insight into manipulating process parameters. The particle size distribution and thermal conductivity of the foams were studied by considering different parameters.

Product characterization and the reaction thermal kinetics were evaluated using differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), particle size distribution and thermal conductivity measurements. The effect of graphite and initiator concentration on the reaction kinetics was investigated.

The results showed that the graphite profoundly reduced the rate of reaction and consequently caused instability in the suspension. By manipulating the process variables such as increasing the amount of stabilizers (1 to 2%) and initiator (up to 0.6% by wt), their frequency and injection time, the polymerization of styrene in the presence of graphite was done. The beads were spherical and the superfine (less than 420 μm) proportion of the product was less than 5%. Through the pre-expansion process, the beads were expanded and the cell structure was uniform. The pentane content of the beads was sufficient (~7% by wt) to successfully sinter the pre-expanded beads in the final molding process. Final foams had 0, 1 and 1.5% graphite. By increasing the graphite content, the thermal conductivity of the foams was decreased. Graphite-containing foams were better thermal insulators than conventional expandable polystyrene. Therefore, for a specific thermal duty, a smaller amount of graphite-containing expandable polystyrene rather than conventional polystyrene is required and consequently, the total cost of the insulation is reduced.