Various applications of modeling in the field of polymerization reaction engineering are demonstrated in this work. The high-pressure polymerization of ethylene is studied using a three-step modeling approach consisting out of a deterministic, stochastic and rheology model. Two industrial tubular reactors are investigated with respect to their productivity and process parameters. Through this, reactor optimization and increase in process understanding is achieved. Design of experiments by simulation for the production of specific polyethylene samples is carried out and validated using a lab-scale autoclave. The modeling approach is adapted and applied for a metallocene-catalyzed polymerization in a solution polymerization mini-plant to model different polyethylene samples. The same mini-plant is described by a calorimetric model to determine the conversion on-line. A new model is developed to describe polyethylene blends based on their microstructure, which can be determined by stochastic simulations. This model is validated by experiments with polyethylene samples from the previous parts.weiterlesen