Volume Viscoelasticity of Polymers and Other Highly Dissipative Materials

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Abstract
A new method for determining the real and imaginary parts of bulk modulus of polymers and other solid materials is represented. The method, as is called “suspension method”, consists of measurements of sound velocity and attenuation in a suspension of powders and is superior in experimental accuracy to the existing method which essentially consists of the comparison of longitudinal and shear wave measurements. The new method has also a merit in the applicability to the sample in powdery state. The results are given for styrene-butadiene rubber, natural rubber, polyethylene, polypropylene, polytrifluoromonochloroethylene, paraffin and yeast cell, among which styrene-butadiene rubber is most fully investigated. From these results, the followings are concluded: In the primary dispersion of amorphous polymers, the relaxation strength is of the same order of magnitude for bulk and shear moduli, and moreover, relaxation times, their distribution and temperature dependence have no appreciable discrepancy between two moduli. In the case of crystalline polymers, the mechanical dispersions are quite different between the power samples which have undergone no treatment after polymerization and the ones moulded from the powder.

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