Dynamic Mechanical Properties of the System Polystyrene-Decalin

Abstract

The dynamic rigidities and viscosities of solutions of polystyrene (number‐average molecular weight 197 000) in decalin have been measured by three experimental methods over ranges of concentration from 10 to 62 percent, of temperature from −5° to 50°C, and of frequency from 30 to 2000 cps. Similar measurements were made on the undiluted polystyrene from 115° to 133°C and 30 to 2800 cps. The data for the solutions, when reduced to a reference state of unit density and viscosity at a standard temperature, provide single composite curves for dynamic rigidity and viscosity. The distribution function of relaxation times calculated from these curves overlaps that previously derived from stress relaxationmeasurements on this system, and the combined function covers a range of time scale of ten powers of ten. It shows the three characteristic regions previously identified in the relaxation distribution function of polyisobutylene; there are no obvious anomalies associated with the fact that decalin is a very poor solvent for polystyrene. The data for the undiluted polymer, when reduced to a standard temperature, provide single composite curves for dynamic rigidity and viscosity. The temperature reduction factors provide apparent energies of activation for relaxation which agree with those for viscous flow obtained by Fox and Flory. The relaxation distribution function of the undiluted polymer is similar in shape to, but somewhat sharper than, those for other polymers in the transition from soft to glassy consistency. When reduced to a reference state of unit density and viscosity, the distribution function of the undiluted polymer lies near that reduced from data on solutions, but is considerably sharper than the latter.