Effect of In-Situ Cure on Measurement of Glass Transition Temperatures in High-Temperature Thermosetting Polymers (Briefing Charts)

Using the dicyanate ester of bisphenol E (also known as Primaset LECy), we have illustrated the difficulties inherent in measurement of the glass transition temperature of this high-temperature thermosetting polymer via dynamic mechanical analysis alone. These difficulties result from the residual cure of samples heated beyond their glass transition temperatures. Comparative DSC and oscillatory TMA studies carried out using a variety of cure conditions showed that simply increasing the heating rate did not suppress the residual cure, although in many cases it allowed the glass transition to become apparent before the onset of rapid residual cure. The results indicated that ensuring the reliability of dynamic mechanical measurements of the glass transition temperature is very difficult to accomplish without the knowledge of residual cure properties provided by methods such as DSC. The original document contains color images. Contains briefing charts only.