| Abstract: | Multiple frequency dynamic mechanical experiments are generated by the linear addition of harmonic sinusoidal waves in order to study the gelation behavior of a crosslinking epoxy–bisphenol-A copolymerization. The following three criteria are investigated as kinetic parameters for the network formation: equivalence of the moduli increase, the critical gel condition, and the mechanical gel condition. The effect of strain magnitude is investigated for both the gelation phenomena and the scaling exponent of the critical gel behavior. The exponent is found to vary from 0.85 to 0.65, depending on the reaction temperature and waveform of the strain input. When Arrhenius type behavior is found, the activation energy of the gelation process is found to be 21 ± 1 kcal/mol. The effects of vitrification, network rupture, and nonlinear viscoelastic response were found with respect to the frequency probe. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 593–600, 1999 |
