From dispersion to powder: Monitoring PMMA latex coagulation with Photon density Wave Spectroscopy (PDWS)

• Real-Time Monitoring with PDWS: Photon Density Wave Spectroscopy (PDWS) successfully enabled in-line, real-time tracking of the coagulation process in PMMA latexes by monitoring changes in the reduced scattering coefficient. • Validation Against Conventional Techniques: The PDWS results were validated using established off-line methods such as laser diffraction (Mastersizer) and Scanning Electron Microscopy (SEM), confirming its reliability in detecting early coagulation events. • Impact of Process Variables: The study systematically analyzed how temperature, salt type (NaCl vs. CaCl 2 ), and salt addition rate influence particle size, morphology, and bulk density—providing valuable insights for optimizing industrial coagulation processes. This study explores the use of Photon Density Wave Spectroscopy (PDWS) as an in-line technique to monitor coagulation experiments of polymethyl methacrylate (PMMA) latexes. The coagulation process was induced by the addition of monovalent (NaCl) and divalent (CaCl 2 ) salts under varying conditions of temperature and salt addition speed. PDWS effectively tracked the evolution of the reduced scattering coefficient, enabling real-time detection of coagulation. The results were validated against conventional off-line techniques such as laser diffraction (Mastersizer) and Scanning Electron Microscopy (SEM). The study demonstrates that PDWS can accurately detect early coagulation events, although limitations exist in calculating the average particle size of the aggregates. The influence of temperature, salt type, and salt addition rate on particle size, morphology, and bulk density was systematically analysed, offering insights into optimizing coagulation processes for industrial applications.