In the last post we described the experimental setup for making simultaneous viscosity (dynamic complex viscosity) and dielectric measurements.  In this post we will dive a bit deeper into how to use this method to probe the physical changes occurring during non-isothermal curing. To demonstrate how the dielectric loss factor changes as a function of fully cured glass ... [Click to Continue...]

In this post will build on the basics presented in Parts 1-4.  Back at IBM I was developing a fundamental understanding of the composite lamination process used to fabricate very expensive multilayer circuit boards.  I was looking for a way to measure the viscosity in-situ during the lamination process but was challenged with how to embed a rheometer in a 10 opening ... [Click to Continue...]

In this post we will cover dielectric cure monitoring during non-isothermal curing.  Since most thermoset processing is done using a non-isothermal temperature profile (such as the initial heating ramp during lamination and autoclave curing), it will be instructive to examine the dielectric response for temperature ramps. In the following figure, the dielectric permittivity ... [Click to Continue...]

In the previous post we discussed the importance of the ionic conductivity as a useful probe of thermoset cure.  In the equation on the left, one observes that the dielectric loss factor, e” is proportional to the ionic conductivity, s.  The term e”d represents the combined  (or lumped) contributions from all dipoles in the curing system. This relationship forms the basis for ... [Click to Continue...]