In situ monitoring of cyclic butylene terephtalate polymerization by dielectric sensing

The in situ monitoring of the polymerization of cyclic butylene terephtalate (CBT) oligomers by dielectric sensing has been investigated under isothermal conditions at different processing temperatures. The change in conductivity depends on the increase of molecular weight but is also influenced by crystallization of the obtained c-PBT during or after polymerization. Dielectric sensing investigations are in good agreement with SEC and DSC analysis which confirm the observation of polymerization and crystallization kinetics. Unfortunately, the conductivity signal could not distinguish between the polymerization and crystallization when they occur simultaneously at lower temperatures (<210 °C) but the crystallization remains detectable by the MWS relaxation which is related to the crystalline/amorphous interface.