EQUIPMENT FOR DIELECTRIC CURE MONITORING

Dielectric cure monitors measure the dielectric properties of material at a single frequency or across a range of frequencies, selectively revealing the influence of mobile ions and dipole rotation. Armed with the data this equipment reveals, users of dielectric cure monitors can make well-informed decisions as they work with advanced materials, moving through the stages of R&D, manufacturing, and quality control processes with confidence and improved efficiencies.  

The figure below shows the essential elements of a dielectric cure monitoring system. Making contact with the thermoset under test, dielectric/conductivity sensors have two general configurations, parallel plate or interdigitated electrodes. The selection of a sensor depends on the desired type of measurement, either surface or bulk, and the desired sensitivity as indicated by the A/D ratio.

Sensors connect to an instrument, and the most versatile instruments use AC signals for composite cure monitoring. A wide range of excitation frequencies allow selection of an optimal frequency for observing ion viscosity, and multiple frequencies enable studies of the dipolar response. Temperature measurement is important for understanding cure, especially under non-isothermal conditions.

Finally, software controls the instrument, usually through a computer connected to the dielectric cure monitor. Thermoset or composite cure state cannot be determined from a single point measurement, but must be extracted from the change of ion viscosity and the shape of the curve over time. So software, which makes repetitive measurements, and stores and analyzes data, is crucial to the performance of the system.