Rheological Characterization of a Silicon Reference Oil Within a Lab-Scale Glass Reactor
Rheological in-situ measurements of chemical reactions (such as polymerizations) can be of special interest because the conversion of their educts to the final products is often accompanied by a vast change in the system´s viscosity. This application report is a preliminary study to show the compatibility of a rheometer with a lab-scale glass reactor. To verify the working principle of this customized setup, a well-known silicon reference oil was chosen and rheologically investigated.
Rheological in-situ measurements of chemical reactions, especially of polymerization reactions, are of high interest and could be a promising, future field of application for this concept. Polymerization describes the chemical reaction of forming polymer chains from monomer molecules.
Polymerization reactions are usually performed using so-called reactors. Such reactors can be made of different materials, like steel or glass. While steel reactors are mechanically stable, glass reactors show some certain benefits. For example, a glass reactor is transparent, so that the reaction can be followed visually. In addition, glass is inert, which makes it useful for aggressive chemicals. On the other hand, the thermal conductivity of glass is limited, which makes it difficult to dissipate heat produced during exothermal reactions.
In Figure 1 a representative lab-scale glass reactor is shown.
During polymerization, the reagent undergoes a vast change in viscosity. This is caused by the progressive increase in length of the molecular chains, which in turn leads to increased entanglement and therefore to higher internal friction. The change in viscosity can be used as a measurement for the progress of the reaction. By determining the ideal moment to add inhibitors, the average polymer chain length can be controlled; and consequently specific material properties customized. By attaching a reactor to a rheometer, the reaction can easily be conducted while simultaneously determining the viscosity of the solution.
The target of this preliminary study is to prove the potential compatibility of an air bearing-based Modular Compact Rheometer (MCR) from Anton Paar with a standard lab-scale glass reactor. To simulate and compare measurement conditions within a lab-scale glass reactor, various measuring geometries were evaluated using a well-known silicon reference oil for the determination of rheological properties.
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