A Simplified Polymerization Model for Fluorinated Polymers: Average Microstructural Properties and Recipe Optimization

Fluoropolymers cover a wide range of industrial applications, due to their valuable mechanical and thermal properties. The microstructure of the final product is the key to controlling its end-use properties and to making them as close as possible to those required by the market. In this work, a model was proposed to evaluate the main average microstructural properties of the polymer, such as the number-average molecular weight and the number of the different chain ends per polymer chain, resulting from formulation parameters like the quantity of initiator, chain transfer agent, and crosslinking agent and corresponding addition policies. A representative kinetic scheme was proposed, involving an iodinated degenerative transfer agent and a crosslinking agent. The combination of these two additives allows tuning iodine incorporation within the chains, a key feature for the product post-processing. The model was first calibrated by fitting appropriate experimental data, then validated by exploiting additional data obtained under different operating conditions. Finally, the model was applied to determine the best feed policies for initiator, chain transfer agent and crosslinker ensuring the desired average properties of the final product. The reliability of the designed recipes was verified by comparison with experimental data obtained by implementing the addition policies predicted by the model.