A model for the structures of impact polypropylene copolymers produced by an atmosphere-switching polymerization process

This work reports on the development of a model to establish the relationship between the structures of impact polypropylene copolymer (IPC), a high performance polymer material, and the characteristics of an atmosphere-switching polymerization process (ASPP), a new polymerization route. To calculate the complex structures of IPC, a detailed kinetic mechanism was proposed to describe the kinetic behavior of the active centers of Ziegler-Natta catalyst during ASPP. The semibatch ASPP for synthesizing IPC was carried out for the model validation. The model is capable of predicting the evolution of the compositional distributions of IPC as a function of switching frequency (SF), which is the main characteristic parameter of ASPP. ASPP not only allows controlling the contents of ethylene-propylene random copolymers (EPR) and ethylene-propylene segmented copolymers (EPS,) but also tuning the composition of EPS. Other applications of the model are discussed.