ASA 126th Meeting Denver 1993 October 4-8

2aSA7. Determination of the static moduli of viscoelastic polymers.

Wayne T. Reader David F. Sauter

Vector Res. Co., Inc., 2101 E. Jefferson St., Ste. 700, Rockville, MD 20852

The characterization of viscoelastic polymers frequently requires determination of the static moduli in addition to determination of the dynamic moduli. A commonly applied method for determining the static Young's or shear modulus is to extrapolate the dynamic modulus in the rubbery regime to vanishing low frequency. A second approach is to relate the hardness, e.g., Shore A, to an estimate of the Young's or shear modulus. As will be briefly described, neither of these approaches appears to provide consistent results. A method is described that exploits the stress/strain hysteresis loop to develop estimates of the static moduli. The method is believed to provide more reliable estimates than obtainable from the previously employed methods. Examples are provided of the method's application to a variety of viscoelastic polymers possessing loss factors varying from about 0.1--1.0, and rubbery moduli varying from 1--10 Mpa. Comparisons are made between the results of the new method and the two previously used ones. [Work supported by ONR 1225AM.]