Determination of time independent component of the complex modulus during cure of thermosetting systems

Abstract

Abstract A recent development suggests an approach to measure the equilibrium modulus through an impulse method. This paper is to report an attempt to apply such methods in measuring the changes of the equilibrium modulus of a thermosetting system during isothermal cures. Dynamic modulus changes were also measured and the results were correlated with that from the impulse method. At two different temperatures of cure, the equilibrium modulus values measured were very similar when the dynamic measurements showed tan δ = 1. At this point, it is not certain if the measured modulus is the real time independent portion of the elastic modulus, or contains the long relaxation time constant portion of the relaxation spectrum which appears to be pseudo‐time independent at the time scale and the instrumental sensitivity of the present experimental set‐up. This paper demonstrates the ease with which the impulse technique can be applied and suggests possible limitations or refinements.