Dielectric Cure Monitoring Applications
When working on a new thermoset, the cure process is essentially unknown. What happens when the material is heated? When is the best time to apply pressure? How fast does the material react at different temperatures? Dielectric Analysis (DEA) complements more conventional thermal analysis techniques of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) to bridge the gap between laboratory and manufacturing environments.
Ion Viscosity and Its use in DEA
Dielectric cure monitoring, also known as DEA, measures a polymer’s resistivity (r) and permittivity (e’), which are the material’s dielectric properties. In general, resistivity provides the most useful information about cure state.
Guidelines for Dielectric Cure Monitoring
Although the method of DEA is simple—place a sample on the sensor, heat and start data acquisition—care and good practice are very helpful for making good measurements. Here are some guidelines for successful dielectric cure monitoring.
Distributed Dielectric Cure Monitoring of Composite Aerospace Structures
Distributed Dielectric Cure Monitoring (D-DEA) is a new concept for the application of Dielectric Analysis (DEA) in manufacturing. Instead of a single expensive base instrument and many long extension cables, D-DEA uses multiple inexpensive instruments connected along a single RS-485 communications line.
Distributed Dielectric Cure Monitoring of Wind Turbine Blades
Distributed Dielectric Cure Monitoring for the first time allows the use of DEA to monitor many locations in very large structures like wind turbine blades and composite beams. Distributed Dielectric Cure Monitoring also avoids the tangle of extension cables used for monitoring parts requiring multiple sensors, such as aircraft and spacecraft components.
Electrode and DC Resistance Cure Monitoring
Dielectric cure monitors measure the electrical properties of a thermoset with AC signals across a range of frequencies. Measurement of resistance with DC methods can also reveal information about a material, but has disadvantages and limitations that the user must consider.
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. Ion viscosity of a material is frequency independent resistivity (rDC) and is often proportional to the change in mechanical viscosity before gelation and proportional to the change in modulus after gelation. Consequently, ion viscosity is a useful probe of material state through the entire cure.
Lambient Technologies LLC, based in Boston, Massachusetts, develops instruments, sensors, and software for monitoring the dielectric properties of curing polymers. These properties provide unique insights into the chemistry, formulation, reaction rate, viscosity, and cure state of epoxies, polystyrenes, polyurethanes, silicones, SMC, BMC, and other types of thermoset materials.
Dielectric cure monitoring, or Dielectric Analysis (DEA), has wide application in research and development, quality assurance and quality control, and manufacturing.
Lambient Technologies’ products are designed for flexibility and ease of use. Together they form an integrated system for studying polymers and optimizing manufacturing processes.
Lambient Technologies was founded in 2008 by members of the team that commercialized products by Micromet Instruments; a Massachusetts Institute of Technology (MIT) spin-off that pioneered the technology of dielectric cure monitoring in the 1980s. Since then, members of our team have developed dielectric cure monitoring products for Metrissa/Holometrix and Netzsch Instruments, giving us more experience in this technology than any other company in the field. Our History