I decided to add a Thursday post this week to break up the rheology series.  I know some of our readers may not be as “into” rheology as some.  We have a long list of pretty technical blog posts scheduled (Dr. Prime will be back with a series of posts on thermoset cure kinetics and Dr. Humphreys will have additional posts on biopolymers).  So I have decided to add in a ... [Click to Continue...]

In the last post we talked about isothermal cure rheology.  This is a good way to look at the curing time, gelation time, and get an understanding of the viscosity temperature dependence, but most commercial thermoset processing methods are non-isothermal.  Whether it is bulk molding compound (BMC) molding, prepreg lamination for composites, or integrated circuit encapsulation ... [Click to Continue...]

Isothermal curing can be investigated nicely using oscillatory parallel plate rheometry.  It is suggested that disposable plates be used to facilitate sample removal from the rheometer at the conclusion of the curing run.  When setting up the rheometer, the strain amplitude needs to be determined.  In most cases, a strain amplitude in the range of 0.1-0.3% is adequate to get ... [Click to Continue...]

Thermoset rheological characterization is typically done using controlled strain experiments.  We discussed this in the Dynamic Mechanical posts in the characterization series.  For rheometry, we use a rotational shear geometry so we are reporting the dynamic loss modulus as G” and the dynamic storage modulus as G’.  As discussed in the previous post, the most common geometry ... [Click to Continue...]

This post will cover the types of rheological measurements available for characterizing thermosets.  Rheology is important in two aspects of thermoset processing.  The first is during the application or dispensing of the uncured thermoset (for example an highly filled adhesive or coating) and the second is characterizing the viscosity changes during the curing process.  In the ... [Click to Continue...]