Fouling Pathways in Emulsion Polymerization Differentiated with a Quartz Crystal Microbalance (QCM) Integrated into the Reactor Wall

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 degrees C), some deposition is always observed. However, a film with a thickness of less than 1 mu m (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.

Automated summary

In situ study of emulsion polymerization fouling at hot interfaces using QCM-D was conducted. The fouling kinetics and surface stabilization were quantified with the QCM. It was observed that a film with a thickness of less than 1 µm can stabilize the surface against the deposition of thicker layers. Furthermore, the increase in resonance bandwidth prior to the main transition was attributed to the first contact of coagulum with the surface. The QCM-D technique proved effective in observing and quantifying the fouling at hot interfaces.