Document Abstract
ANTEC Papers: 1999
891: Cure Monitoring of Phenolic Resins Using Dynamic Rotational Rheometry
J. L. Rose a and M. T. Shaw a,b Department of Chemical Engineering a and Polymer Program b Institute of Materials Science, University of Connecticut Storrs, CT 06269
The mechanical responses of two phenolic thermoset resins during curing were monitored as a function of time and temperature using dynamic rotational rheometry. The tangent of the phase angle tan d, the ratio of elastic to viscous modulus, was used to characterize the reactions because of foaming and emission of by-products. For resole phenolic resins, gelation was interpreted as the cross-over of the storage and loss moduli, i.e. tan d=1. This assumption proved to be reasonable, as activation energies derived thereby agreed with those found using in-line ultrasonic measurements. The gelation time of the novolac resin was successively assumed to be the first occurrence of tan d=1 or the minimum of tan d. The activation energies found using these assumptions were both significantly higher than those found using ultrasonic measurements. Resolution of this discrepancy may require a knowledge of the influence of the foam structure on tan d.