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Advisor(s)
Abstract(s)
The synthesis of super-absorbent hydrogels is simulated using a kinetic
model based upon population balance equations of generating functions. Dynamics
in a batch reactor of properties such as the weight fraction of gel or average
molecular weights of the soluble fraction can be predicted. This kinetic model
neglects intramolecular cyclization reactions for simplicity (hence predictions can be
valid only for very small amounts of crosslinker) but it can accommodate the
operation with different kinds of crosslinking agents, namely bifunctional (e.g. N,N0-
methylenebisacrylamide), trifunctional (e.g. trimethylolpropane triacrylate) and tetrafunctional
(e.g. tetraallyloxyethane). The influence of the use of such different kinds
of crosslinkers on the dynamics of gelation is discussed. It is also assessed the
impacts of the rate propagation coefficient of the monofunctional monomer
(typically acrylic acid), of the reactivity of the pendant double bonds (PDB) and of
the initial composition on the dynamics of gel production. Some crucial details
concerning the numerical solution of the two-point boundary value problems (TPBVP)
associated with this simulation tool are also presented. Predictions of the proposed
kinetic approach are compared with those obtained using the Theory of the Branching
Processes which is not strictly valid with kinetically controlled polymerization
systems such as those here considered. Important differences between the predictions
of the two approaches are shown. Superabsorbent hydrogels were synthesized
with a 2.5 L batch reactor and the experimental data are used to show that the simple
kinetic model developed is able to capture the main features of this polymerization
system.
Description
Keywords
Hydrogels Kinetics (polym.) Modeling
Citation
Gonçalves, M. A. D.; Pinto, V. D.; Dias, Rolando;Costa, Mário Rui (2011). Studies on the synthesis of superabsorbent hydrogels using population balance equations. In Macromolecular Symposia. ISSN 1521-3900. 306-307, p. 107–125 e 20th Conference on Polymer Networks Group. Goslar
Publisher
Wiley-VCH