Monitoring the Degree of Conversion of Cyclic Butylene Terephthalate using Dielectric Analysis

Dielectric analysis (DEA) is the most common technique used to determine the state of cure in-process for many thermosetting resins systems such as epoxies, polyesters, polyurethanes, polyimides, silicones, bismaleimides, and phenolics. The objective of this work is to investigate the processing characteristics of cyclic butylene terephthalate (CBT) (supplied by Cyclics Corporation) which polymerises to form a thermoplastic, polybutylene terephthalate (PBT). This paper reports on the interim results of ongoing experimental investigations in which DEA is used to correlate the process cycle to composite structural features and mechanical performance of a complex composite part. Through adjustments in process cycle, the significant processing parameters have been identified which optimise the production of thermoplastic PBT composite parts. The recorded ion viscosity is used to indicate change in material viscosity, conversion rate and process time. These results have been analysed and presented as a guide for correct process control.