Chemistry of Chain Scission

To discuss the thermodynamically induced shear degradation in further detail, we first turn to the chemistry of mechanical chain scission. The next step is the comparison of the experimental results with different breakage models according to the method developed in Sect. 3. Then, the dependence of chain scission on various parameters as the applied shear rate, concentration, and temperature will be discussed in detail. 

The scission of the carbon-carbon bond induced by mechanical action is homolytic in practically all cases studied so far. This was proven by the consumption of stable free radicals during the ultrasonic degradation of various polymers (see, for instance. Ref. A number of years ago Henglein s able to elucidate some of the 

The marked difference of the observed kinetics of degradation is even more pronounced at lower shear rates as is obvious from Fig. 15. 

At present, the most plausible explanation may be sought in the alterations of solvent quality by DPPH through preferential adsorption onto the chains. This would lead to an improvement of solvent qualitj and the results obtained in the presence of DPPH may be compared with those obtained using at a greater distance to the demixing temperature. A more detailed discussion of this point is given in Sect. 6.6 when considering the influence of AT. 

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