In reaction engineering, "fouling" denotes the unwanted formation of deposits on surfaces.  Examples are lime deposits in pipelines or biofilms.  Polymer fouling is a major problem in the production of latex dispersion, i.e. colloidal particles in water.  Thin polymer layers always form on the walls of the reactor.  As long as these layers remain thin, they are not a problem.  The problem arises when the layers become so thick that they impede heat transfer through the wall and, in the worst case, even clog the pipes.  The fouling problem currently prevents the production of latex dispersions in continuous flow in tubular reactors.  Large tanks are used in batch mode.

The group has recently established a method to follow the formation of fouling layers in emulsion polymerization in-situ.  The quartz crystal microbalance (QCM) is used.^[1]  It was shown - not unexpectedly - that the fouling layer is sometimes self-limiting in its growth, but that it is not in other cases.  What conditions lead to the catastrophic growth of the layer is poorly understood.  The QCM allows to follow the growth during the reaction.  In particular, there is evidence of compactification during the formation of the layer.^[2]  Such a compactification can be better understood in the context of particle fouling than in the context of reaction fouling.  Following this interpretation, particle fouling dominates in the cases studied so far. Polymer particles first form in the liquid, and later attach to the surface.  Polymerization directly at the surface plays a minor role.

We pursue this work further within the DFG project JO 278/25-1 (together with AK Scholl, TU Braunschweig).

1. Böttcher, A.; Petri, J.; Langhoff, A.; Scholl, S.; Augustin, W.; Hohlen, A.; Johannsmann, D., Fouling Pathways in Emulsion Polymerization Differentiated with a Quartz Crystal Microbalance (QCM) Integrated into the Reactor Wall. Macromolecular Reaction Engineering 2022, 16, (2).
   
   
2. Johannsmann, D.; Petri, J.; Leppin, C.; Langhoff, A.; Ibrahim, H., Particle Fouling at Hot Reactor Walls Monitored In-Situ with a QCM-D and Modeled with the Frequency-Domain Lattice Boltzmann Method. Results in Physics 2023, 45, 106219.