During the synthesis and processing of polymers, a significant amount of polymer may be deposited on the heat transfer surfaces. This deposit is unwanted and is usually named fouling. This study deals with the fouling behavior of a vinyl acetate/vinyl ester copolymer during emulsion polymerization and compares this to fouling of an already reacted vinyl acetate/ethylene copolymer dispersion. Besides the state of polymerization, also the influence of the wall temperature is investigated. The experiments are performed on cooled and heated surfaces. The deposition process is quantified by the mass‐based fouling resistance, the height of the fouling layer, and the surface coverage using a digital microscope. It is found that the state of polymerization and the temperature gradient between wall and bulk exert a strong influence on the fouling behavior, especially on the structure of the fouling layer.

Emulsion polymerization fouling at hot interfaces is studied in situ, making use of a quartz crystal microbalance with dissipation monitoring (QCM-D). The resonator crystal is heated with a ring-shaped thermal pad from the back, turning it into a plate with elevated temperature. Configured to be one of the walls of a small reactor for emulsion polymerization, this resonator is prone to heat-transfer fouling, similar to regular heated parts of process equipment. The fouling kinetics is readily quantified with this QCM. During polymerization at constant temperature (80 °C), some deposition is always observed. However, a film with a thickness of less than 1 𝝁m (determined gravimetrically with the QCM) is sometimes found, which stabilizes the surface against the deposition of much thicker layers. When reaction fouling proceeds directly to thick deposits, a small increase in resonance bandwidth often occurs a few minutes prior to the main transition, presumably caused by coagulum formed in the bulk making first contact with the surface. Furthermore, particle fouling is studied with temperature ramps on nonreactive dispersions. Fouling, if present, is readily observed.

Zur Untersuchung der unerwünschten Belagbildung von Polymeren auf wärmeübertragenden Oberflächen (Polymerisationsfouling) wird das Ablagerungsverhalten eines Vinylacetat/Vinylester-Copolymers während der Emulsionspolymerisation untersucht. Hierbei sollen grundlegende Unterschiede zum Ablagerungsverhalten eines bereits reagierten Vinylacetat/Ethylen-Copolymers identifiziert werden. Für einen qualitativen Vergleich wird die Ablagerungstopographie mithilfe eines Digitalmikroskops bestimmt. Für die quantitative Berechnung wird der Foulingwiderstand aus der Masse sowie der Schichthöhe des abgelagerten Materials berechnet. Der Polymerisationsgrad beeinflusst das Ablagerungsverhalten insb. die Topographie. Das bereits ausreagierte Stoffsystem weist eine größere Foulingmasse sowie eine deutlich ausgeprägtere, kraterförmige Ablagerungstopographie auf, wohingegen während des Polymerisationsfoulings eine optisch deutlich andere, tropfenförmige Topographie entsteht.To investigate the unwanted deposition of polymers on heat transfer surfaces (polymerization fouling) the deposition of a vinyl acetate/vinyl ester copolymer during emulsion polymerization is investigated. The aim is to identify fundamental differences to the fouling behavior of an already reacted vinyl acetate/ethylene copolymer. For a qualitative comparison the surface coverage is observed using a digital microscope. For the quantitative examination the fouling resistance is calculated from the mass and the layer height of the deposited material. The degree of polymerization has a significant influence on the deposition behavior. The already reacted material system shows a larger fouling mass and a more pronounced, crater-shaped surface coverage, whereas during polymerization fouling a clearly optically different drop-shaped surface coverage was formed.

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