Transitiometry as an Advanced Tool for Kinetic Analysis and Design of Peroxide Initiator Cocktails for High-Pressure LDPE Polymerization

The decomposition kinetics of peroxides and their cocktails under relevant process conditions for radical high-pressure polymerization of ethene are investigated and determined. Further, various influencing factors affecting this process are examined. The aim is to understand and evaluate the processes involved on a large industrial scale, enabling the generation of data for possible process simulations on the one hand. On the other hand, it allows adressing the topic of cocktail design, with a view to later creating cocktails for specific large-scale technical applications. For measuring the kinetic data, the high-pressure calorimetric method called transitiometry is employed, which ensures high reproducibility of the results and good resolution of the measurements at high pressure and high temperature conditions, making it advantageous compared to alternative calorimetric methods. The results reveal the decomposition behavior of a wide range of organic peroxides, each of which exhibits different kinetics and decay curves. The choice of peroxides therefore offers a wide range of cocktails to be generated with highly variable radical generation spectra. The study is able to demonstrate that the decomposition behavior of individual peroxides can differ greatly compared to the same peroxides in a mixture with others. Partial prediction of some decay curves has been possible, whereas prediction of kinetics is rather difficult and should be the subject of further investigation. This work lays the foundation for a better understanding of peroxide cocktail decomposition under the process conditions of LDPE polymerization.