Spontaneous boiling up as a specific relaxation process in polymer–solvent systems
✍ Scribed by Pavel V. Skripov; Stanislavs E. Puchinskis
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 610 KB
- Volume
- 59
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
The phenomenon of spontaneous bubble nucleation in extremely supersaturated (superheated) polymer-solvent systems has been studied experimentally. Spontaneous boilingup temperatures T* for polystyrene and poly(ethy1ene glycol) solutions in a number of solvents have been measured at different values of pressure p and weight fraction of polymer c by the pulse heating method. The heating rate T varied from 10' to lo7 K/s. For all systems studied, the values of T* have been found to increase with increasingp and c. The T*(p, c) dependence is discussed with the use of the data on the degree of compatibility of components. The peculiarities of polymeric solutions manifest themselves in the region c + 1, as follows: (i) an abrupt increase (by 1-2 orders of magnitude) in the slope of the T*(c) dependence, and (ii) the appearance of the dependence of T* values on the heating rate. Our approach to the interpretation of this result assumes a change in the initial composition of a solution in the course of heating due to polymer decomposition. An example of the extended phase diagram of a polymer-solvent system including the kinetic surface of T*(p, c ) is given.