G. Fevotte et al., NONLINEAR TRACKING OF GLASS-TRANSITION TEMPERATURES FOR FREE-RADICAL EMULSION COPOLYMERS, Chemical Engineering Science, 53(4), 1998, pp. 773-786
A new method for the control and estimation of the glass transition te
mperature (T-G) of free-radical copolymers is presented, and is intend
ed to improve the on-line control of the quality of these products. As
an example of this approach, a non-linear control law is used to mani
pulate the monomer feed flow rate of semi-batch copolymerisation in em
ulsion in order to pursue a predefined trajectory of T-G. The measured
output required for an effective closed-loop system is provided throu
gh calorimetric measurements of the overall monomer conversion, and bo
th the number of moles of monomer and the total number of radicals in
the polymer particles are estimated using non-linear observation techn
iques. The global approach is based on a simplified kinetic model of t
he emulsion copolymerisation of water-insoluble monomers, which was va
lidated through laboratory scale experiments. In addition to the overa
ll and partial conversions, the model also predicts the time variation
s of the instantaneous copolymer composition and T-G and of the averag
e particle size. The state and parameter observer was evaluated with b
oth simulated and real polymerisation data, and is shown to perform ve
ry well. The tracking ability of the non-linear control strategy was f
ound to be robust and accurate despite uncertainty and noise in both t
he simulated model and experimental measurements. (C) 1998 Published b
y Elsevier Science Ltd.