(382a) Modelling of Ultrasonic Polymer Degradation Using Continuous Kinetics

The degradation of polymers has a large impact on the application of these polymers, especially on the long-term stability. In the past, several experiments regarding to the ultrasonic polymer degradation were performed, where the degradation is influenced by the temperature and the ultrasound intensity [1]. In the case of polystyrene, it was figured out that the degradation rate depends on the initial molecular weight [2], the kind of the solvent [2,3], solvent concentration [3] and dissolved gases [3]. From the thermodynamic point of view, the impact of the solvent and the dissolved gases are interesting. It will be desirable to predict this impact using thermodynamic quantities.

On the other hand, kinetic models based on continuous kinetics which are directly based on continuous distribution function of the initial polymer are available [5]. These method allows the calculation of the distribution function at every time. However, the model require an equation for the description of the scission probability k(M,M') in its dependence on the molecular weight of the polymer and the location of the bond to be broken within the molecule. These equations contains parameters which must be adjusted to experimental data.

The basic idea of this contribution consists in the application of this model [5] to the experimental data for the ultrasonic degradation of polystyrene available in the literature [2-4]. We focus our attention to incooperate the thermodynamic properties of the solvent in the expression k(M,M') in order to achieve a possibility to transfer this expression to other solvents. The impact of different thermodynamics properties, like speed of sound as well as the interaction of the solvent with the polymer, will be discussed.

[1] A.M. Basedow, K.H. Ebert, Adv. Polym. Sci. 22 (1977) 83-148.

[2] G.J. Price, P.F. Smith, Polymer International 24 (1991) 159-164.

[3] G.J. Price, P.F. Smith, Eur. Polym. J. 29 (1993) 419-424.

[4] G.J. Price, P.F. Smith, Polymer 34 (1993) 4111-4117.

[5] D. Browarzik, A. Koch, J. Macromolecular Sci. A 33 (1996) 1633-1641.