A second classical control problem is the control of the residual monomer content (monomer conversion) of the polymer productivity.
Max. conversions are achieved through increase in residence time, batch time and is limited by viscous effects, diffusional effects.
Min. residual monomer is required because max. conversion leads to max. productivity and also there are some constraints of EPA about VOCs in the products.
This limiting concentration is usually much lower than the one achieved during polymerization, which means that additional post-polymerization treatments are required. As these are costly operations, it is interesting to minimize the amount of monomer at the end of polymerization (maximize monomer conversion).