Determination of inline-particle sizes by turbidity measurement in high solid content emulsion polymerisations

Abstract

Particle size determination in optically dense systems requires costly techniques or dilution of collected samples. Against this background, turbidimetry was investigated as a potentially robust as well as inexpensive alternative. Emulsion copolymerisations of vinyl acetate and VeoVa10® with solid contents up to 48 wt% were examined time resolved with respect to mean particle size at different temperatures, solid contents and with different co-monomer ratios and emulsifier concentrations. The mean hydrodynamic diameters were validated by dynamic light scattering (DLS). Precise number mean hydrodynamic diameters in the range from 100 to 250 nm were obtained in-line for polyvinyl acetate dispersions with deviations in particle sizes below ± 5%. In addition, the turbidity values were recorded by means of a nephelometry process probe and thus a robust, system-related calibration was created, which was subsequently able to reliably track the number mean hydrodynamic diameter inline time-resolved.