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An apparatus has been developed for the measurement of the dynamic mechanical properties of foamed materials impregnated with viscous fluids over a wide frequency and temperature range. Preliminary results are given for two foams. Measurements of rolling friction on foam-fluid substrates have also been obtained in two ways for a number of low-density foams. They are compared with the predictions of a simple theoretical treatment of rolling friction on viscoelastic substrates. An analysis is given of the distributions of stress and displacement in solid rubber blocks subjected to small compressions between rigid frictional surfaces. Particular consideration is given to local sliding motions in the outer regions of the loaded surfaces, as a possible means of energy dissipation. Preliminary experimental measurements of the amount of sliding are reported. (Author)

Delayed buckling of a viscoelastic material was investigated experimentally as a function of buckling load, time, and temperature. The concept of 'Reduced Variables' was shown, for the first time, to be applicable to this physical phenomenon. Linear viscoelastic analysis was employed to give a qualitative and a semiquantitative description of the buckling process and the prediction of the critical time to buckle. (Author)

Apparatus has been developed to measure the dynamic mechanical properties of foamed materials filled with a viscous fluid, over a frequency range from 0.002 to 200 Hz and a temperature range from -50 o C to +100 o C. Measurements have been made on various foam/ fluid systems including rubber latex, polyether and polyester foams filled with air, glycerin, silicone oil and water. The Gent-Rusch theory has been modified to take into account inertia effects, damping in the matrix material itself, and special features of the text-piece assembly . The theory is shown to describe the measurements successfully and verifies the engineering validity of the approach outline. (Author-PL)

Isothermal crystallization rate data for polypropylene films are obtained by a rapid scanning x-ray diffraction technique. These are compared with previously obtained data on similar samples of the same polymer by microscopic observation of spherulite nucleation and growth rates. The degree of crystallinity is found to increase more slowly than the weight fraction of the sample filled with spherulites, indicating that all of the crystallization does not occur at the growing spherulite surface. A mechanism for this secondary crystallization process occurring within the spherulite is proposed in which the spherulite first forms with an initial degree of crystallinity, and then the crystallization continues approaching a limiting degree of crystallinity. The kinetic parameters characterizing this secondary process are determined and their variation with temperature is studied. (Author)