In our last post we discussed the concept of vitrification and the impact on the cure kinetics (dramatic slowing of the reaction rate in the glassy state).  When examining curing data such as the Tg versus cure time plots from the last post, it is often helpful to create a “master curve.”  Remember the Tg-time relationships had the same shape but appeared to be shifted along ... [Click to Continue...]

Vitrification, now that’s an interesting word to use in a thermoset polymer discussion.  The Merriam-Webster online dictionary defines vitrify as “to convert into glass or a glassy substance by heat and fusion.” In the case of thermosets, the definition is pretty close, since the glassy state can be obtained during cooling from the rubbery state and as we will see in this ... [Click to Continue...]

In the last two posts, Dr. Prime discussed gelation and the relationship of functional group conversion at the gel point.  Understanding the conversion at gelation has practical ramifications in many thermoset processes.  As noted in a previous post, in the case of five minute epoxy, five minutes is the gel time.  During thermoset processing, the ability to flow essentially ... [Click to Continue...]

Guest Post by Dr. R. Bruce Prime In the last post we introduced the concept of gelation. Since gelation is the practical endpoint during thermoset processing, it is important to understand how the chemistry and stoichiometric ratios impact the conversion at the gel point.   First to review, gelation is the point during cure where a viscous liquid becomes a ... [Click to Continue...]

Guest Post by Dr. R. Bruce Prime As a result of the chemical reactions discussed in earlier posts thermosets cross-link and become “set”. At a well-defined point in the cure reaction the thermoset transforms from a viscous liquid to a cross-linked gel or rubber, i.e. it gels. Gelation is the incipient formation of a cross-linked network, and it is the most distinguishing ... [Click to Continue...]