Effect of Silica Nanoparticles on the Esterification Reaction

5 Modeling the Effect of Silica Nanoparticles on the Esterification Reaction 

Furthermore, modeling of the esterification reaction was attempted in the presence of silica nanoparticles during the formation of aliphatic polyester nanocomposites. From the experimental data, it was found that on increasing the Si02 content in esterification, the rate of water production decreases [47]. In addition, it was clear that the total quantity of water released does not depend on the nanoparticle concentration. This suggests that the existence of the particles does not influence the esterification reaction itself. Their main effect is to adsorb the produced water before it evaporates, altering in this way the water evaporation curve. The simplest model for this phenomenon is to assume very fast water adsorption/desorption kinetics on the Si02 particles. In this case, the evaporation kinetics must be explicitly taken into account because it is no more very fast compared to the other phenomena that occur. 

The equation derived to express the variation of the extent of esterification reaction including adsorption/desorption of water on Si02 particles takes the following form [47]  

In order to estimate it, a sorption/desorption model is employed. Since from experimental data it was found that water is slowly desorbed from the silica particles mainly at high reaction times, a complicated model taking into account the finite rate of water desorption was considered. Accordingly, T is used to 

Modeling the Polycondensation Reaction Kinetics for the Synthesis of Aiiphatic Polyesters 

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