VIS-optical reflectometry: a method to investigate latex-based coatings

In many applications, water-based dispersions of polymeric particles are dried under well-defined environmental conditions and/or technologies to form a continuous thin layer with special properties and morphology. The aim of this work is to present a recently developed noninvasive technique based on optical reflectometry in visible range used to study the film formation from aqueous mixtures layered up to 25 μm thickness. The sample holder is made of crystalline silicon (c-Si) because the interference fringes generated by the optical beams reflected at the air/liquid sample and liquid sample/c-Si are vital in determining the sample thickness. For the polymeric colloids with minimum film formation temperature higher than the room temperature, the setup is used to determine the evaporation rate and the temperature film formation. The versatility of the experimental setup is increased by a controlled temperature of the sample holder and a controlled microclimate chamber (temperature and relative humidity). Investigations on various aqueous dispersions considering the composition, the viscosity of the liquid, and different types of polymeric colloidal particles have been performed, and some results are discussed here. New challenges lie in analyzing the outputs of the experiments considering the interparticle distance and interparticle interferences.