Sensitivity Analysis of Single-Phase Isothermal Free Radical-Induced Grafting of Polyethylene

Radical-induced grafting of polyethylene involves many reactions such as initiator dissociation, hydrogen abstraction, graft chain initiation, graft (de)propagation, crosslinking, and homo(de)polymerization. To ensure a successful grafting, both the reaction rate and degree of grafting functionalization need to be sufficiently high, implying a design of the process conditions. In the present article, assuming isothermal conditions and a single-phase reactive system, it is demonstrated that the grafting kinetics is influenced by the hydrogen abstraction rate coefficient, the depropagation equilibrium coefficient K-eq , and the initial mass fractions of monomer, initiator, and polyolefin. It is shown that the reaction extent is a consequence of the interplay of the initial monomer mass fraction and K-eq , and the average grafting length is determined by grafting from and to, with longer grafts being formed through grafting to. Close to equilibrium, the average graft length decreases and the crosslinking density increases provided that initiator is left. Moreover, the chain length distribution of the virgin polyolefin strongly influences the molecular arrangement of the grafting points along the polyolefin chains. This can be demonstrated from the hydrogen abstraction reaction event history of polyolefin chains.