| Abstract: | The goal of this work was to investigate the increase in the rate of polyesterification that takes place as surface-to-volume ratio is increased. The polymer used in this reaction was derived from the esterification of adipic acid (hexanedioic acid) and propylene glycol (1,2-propanediol). The effect of three variables—film thickness, water concentration of the nitrogen atmosphere, and temperature—was studied to determine their effect on the reaction rate. The water content of the atmosphere was found to severely retard the progress of the esterification and this fact reaffirms that the reverse reaction, hydrolysis, is much more important than was realized by earlier investigators. The reaction in the film was found to have an activation energy of 22,600 cal/mole compared to 12,600 cal/mole in the batch reaction, indicating a possible change in controlling rate from the batch to the film system. New evidence was found which illustrates the possible role of reactant mobility at high conversions. It is suggested that a possible explanation for the change in controlling rate may be due to a complex surface phenomenon such as the alignment of reactive groups at the surface or the orientation of water molecules at the gas–liquid interface. |
