Elastic Moduli and Poisson Ratio of Amorphous Organic Polymers

Using the pulsed molecular acoustics method, the velocity of longitudinal and lateral sound waves in amorphous organic polymers is measured. The elastic moduli and Poisson ratio, as well as the previously introduced effective elastic modulus, are determined. It is shown that for amorphous polymers the ratio of the bulk modulus to the effective elastic modulus is a single-valued function of the Poisson ratio. The effective elastic modulus is closely related to the Grüneisen parameter, a measure of anharmonism. The nature of the Poisson ratio of amorphous polymers is considered.