Determining the compacting of latex films upon drying by interference measurements — an approach for the investigation of film formation

Abstract

The decrease of optical thickness of drying latex coatings is measured interferometrically. Through data processing film thickness and polymer volume fraction are obtained, which are a measure of particle spacing and deformation. The applied criterion for film formation is the attainment of a dense polymeric material. In this sense the method can be used to check film formation under a variety of conditions. The kinetics of film formation is monitored as well. Since the method is sensitive to changes in optical properties, different modes of drying can be distinguished. The solids content determined by this method is not averaged over the whole film but represents the exact state of drying at the measured spot. Another advantage is that due to the simple setup of the experiment, it works under a broad variety of conditions and without restrictions regarding the nature of the latex. Also, simultaneous measurements at two angles of incidence allow refractive index independent data interpretation. Drying of different dispersions, both film forming and non-film forming under the given conditions, has been investigated, demonstrating the potential of the technique.

Internal Stresses during Film Formation of Polymer Latices

“…This material was synthesized specifically for research purposes and therefore designed with the greatest possible simplicity as far as additives and components are concerned. Details of the preparation are described in refs and 27. The particle size was d w = 130 nm as determined with photocorrelation spectroscopy, and the size dispersity was d w / d n = 1.08.…”

Film formation of heterogeneous latex systems—a comparative study by mechanical testing, electron microscopy, interferometry and solid state NMR

“…Expression of n as a function of the current polymer volume fraction f with and f \ f 0 t 0 /t ( f 0 are initial values) and recalculation of by using the Ðnal t 0 t 0 Ðlm thickness and the thickness change allows one to monitor the compacting during drying. 16 The reÑected intensity (j \ 633 nm) was recorded using a diode detector connected to a Prema 4000 digital multimeter. The Ðnal thickness of the dried Ðlms was measured by using a Tencor-Alpha Stepper 200.…”

“…It is, however, worthwhile noting that the Ðnal occupied volume in coatings of homoH1 reaches 0.88 (after crack correction, see ref. 16). This demonstrates that the presence of soft particles disturbs the hard particle packing and that hard particles do slightly deform.…”