Insulation aging characteristics as measured by shearing modulus

A method is described for determining the effect of thermal aging on the shearing modulus of flexible sheet insulations by nondestructive tests using a torsion pendulum technique. The test sample, in tape form, is simple and easily prepared. Shearing modulus of the material is determined with the tape functioning as the stressed element in a simple torsion pendulum. Equipment for sample preparation and testing is inexpensive and compact, allowing investigations of many materials with minimum expense and effort. The data obtained by this method of test are of particular value and interest in determining the effect of time and temperature on an important mechanical property of flexible sheet materials. Since tests may be made as a function of aging on a given sample, the technique is very useful in establishing deterioration rates of the shearing modulus for a given insulation. Data have been obtained upon materials of widely different temperature classifications in order to demonstrate the usefulness of the technique.