Experimental evidence is given for the mechanism of film formation from industrial waterborne latices using Inverse‐Micro‐Raman‐Spectroscopy (IMRS). In the vertical direction of the film drying is gas‐side controlled, indicated by uniform water concentration profiles. In the horizontal direction inhomogeneous drying resulting from a horizontal mass flux toward the edge of the film and the formation of a drying front are observed. The completeness of film formation is tested by so‐called IMRS redispersion experiments. For hard latices (Texperiment ≃ Tmff) particle deformation is incomplete and the final coating—although transparent and optically clear—is a porous structure with a network of surfactant material located at the particle interfaces. The use of a film‐forming aid lowers the polymer's minimum film formation temperature (Tmff) and facilitates particle deformation and polymer interdiffusion. The result is a nonporous film structure where individual particles and a network of surfactant material are no longer observed. IMRS redispersion experiments are compared with pictures of the final coating surface obtained from atomic force microscopy (AFM). © 2007 American Institute of Chemical Engineers AIChE J, 2007

Concerning quality and drying time of a process the key issue is the progression of the concentration profiles within the film during drying. This contribution reports on the development of a new measuring technique, an Inverse-Confocal-Micro-Raman-Spectrometer, for online measurements of concentration profiles during drying in thin (5-200 mm) polymeric solvent coatings. The spatial and temporal resolution of the measurements is up to one micron and one second. A calibration method has been developed by taking Raman spectra of different, precisely concentrated samples in sealed ORDER REPRINTS quartz glass cells and by calculating the ratio of the intensities of the characteristic Raman peaks. The accuracy of this basic calibration method is very good over a wide concentration range. Initial investigations were carried out on the polymer solvent systems: polyvinyl acetate(PVAc)-toluene, PVAc-methanol, PVAc-benzene, and PVAc-methanol-toluene, PVAc-methanol-benzene.

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