An Interesting Experiment Using the Time Temperature Transformation Diagram The previous post discussed the dielectric and rheological changes during non-isothermal curing.  In this post we will use the information presented so far in this series and present a very interesting case study on how dielectric measurements in conjunction with complex viscosity measurements can ... [Click to Continue...]

Non-Isothermal Curing During many thermoset processing steps (and in this example, lamination of a B-staged (partially cured) prepreg, a non-isothermal temperature ramp is used in the process.  The viscosity profile for the B-staged prepreg at a heating rate of  10°C/minute to a cure temperature of 175°C is shown in Figure 1. Figure 1. Viscosity as a function of time ... [Click to Continue...]

In the previous posts, the basics of dielectric analysis was presented. Part Three of this series will demonstrate the relationships between dielectric data during isothermal curing.  First, let’s examine the isothermal during process. A nice example is the work of Bidstrup, Sheppard and Senturia at MIT in 1989 [1]. They examined the isothermal curing of DGEBA and DDS: ... [Click to Continue...]

Part two of this series will cover the basics of curing monitoring using dielectric spectroscopy.  For cure monitoring, we are going to focus on the dielectric loss factor. The dielectric loss factor is given by: From the above relationship, one observes the dielectric loss factor is comprised of two components: one from ionic conductivity and one from the contributions ... [Click to Continue...]

Thermosets derive their usefulness from the ability to start as a low viscosity resin formulation and through a curing process via well-defined chemical pathways transform into a highly crosslinked network.  The final properties of the crosslinked networks such as the glass transition temperature (Tg) and the moduli can be tailored via the choice of monomers and curing agents ... [Click to Continue...]