Influence of CO₂ on ultrasound‐induced polymerizations in high‐pressure fluids

Abstract

Abstract A strong viscosity increase upon polymerization hinders cavitation and subsequent radical formation during an ultrasound‐induced bulk polymerization. Ultrasound‐induced radical polymerizations of methyl methacrylate (MMA) have been performed in CO 2 ‐expanded MMA, as well as in bulk MMA. For this purpose, the phase behavior of CO 2 /MMA systems has been determined. With temperature oscillation calorimetry, the influence of CO 2 on the viscosity and on the reaction kinetics of ultrasound‐induced polymerizations of MMA has been studied. In contrast to polymerizations in bulk, this technique shows that a low viscosity is maintained during polymerization reactions in CO 2 ‐expanded MMA. As a consequence, a constant or even increasing polymerization rate is observed when pressurized CO 2 is applied. © 2005 American Institute of Chemical Engineers AIChE J, 2005