THERMOACOUSTICAL PARAMETERS OF POLYMERS AT LOW-TEMPERATURES

The Moelwyn-Hughes parameter has been utilized to evaluate a number of thermoacoustical parameters, viz., the Beyer nonlinear parameter; the isothermal, isobaric, and isochoric Gruneisen parameters; the repulsi ve exponent of intermolecular potential; the molecular constant; the f ractional available volume; the Sharma thermoacoustical parameter So; and the Anderson-Gruneisen parameter for a wide variety of polymers at different low temperatures. A relationship among the isobaric, isothe rmal, and isochoric microscopic (lattice) Gruneisen parameters has bee n examined and analyzed in the case of several polymers. The results h ave been used to develop understanding of the significance of microsco pic factors such as molecular order and intermolecular forces upon mac roscopic thermoacoustic properties. The parameter S0 remains invariant with temperature over a wide range and retains, on average, a constan t value of 1.10 for several polymers at low temperatures, similar to a wide variety of substances. The present treatment has the distinct ad vantage that several thermoacoustic parameters can be evaluated from t he knowledge of volume expansivity data alone. (C) 1994 John Wiley & S ons, Inc.