(20e) Influence of Simplifying Assumptions On Solubility Studies in Polymers

Reaction engineering calculations are often based on estimations with quite a few underlying simplifying assumptions. Students may know this and still not realize the corresponding impact. If, for example, virtually all simplifications move the estimation result away from the true value in the same direction, the systematic error may be all from severe to plain prohibitive.

In an advanced student assignment, the solubility of gases in polymers is studied. Knowing it is crucial for proper understanding of many multiphase polymer systems. When evaluating raw data from proper experiments, the first estimate that is extracted does indeed rely on numerous assumptions as described above. The ideal gas law is assumed to be a satisfactory approximation, as are the isothermicity of the system, stationarity of the final state, or the polymer having a constant volume and no swelling. After this first estimate, the simplifications made are replaced step by step by more sophisticated - and realistic - approaches. For a given model system, the dissolution of carbon dioxide in a polymer, the impact of the simplifications on the calculated solubility data is demonstrated. A critical assessment of literature data proves helpful in gauging the implications on subsequent modeling. Furthermore, the students can deduce what experimental setup is most (or least) suitable to generate high-quality raw data.

The work was supported by the BMBF in the Dream Production joint project, which is gratefully acknowledged.