Patterned surfaces in the drying of films composed of water, polymer, and alcohol

Abstract

A study of the complex drying dynamics of polymeric mixtures with optical microscopy and gravimetric measurement is presented. Droplet formation is observed, followed by a collapse that leads to the residual craters in the dried film. The process is followed in situ under well-defined temperature and hygrometric conditions to determine the origin and nature of these droplets and craters. The drying process is usually completed within 1 h. The observations are explained using a simple diffusion model based on experimental results collected from mass and optical measurements as well as Raman confocal microspectrometry. Although the specific polymeric mixtures used here are of interest to the cosmetic industry, the general conclusions reached can apply to other polymeric aqueous solutions with applications to commercial and artistic painting.

Drying colloidal systems: Laboratory models for a wide range of applications

“…We have established [55] that the structuring of cosmetic aqueous films could originate in the demixing of the agent X W with the water present in the film. This phase separation occurs when the mass fraction w X reaches the solubility limit of X W in the film.…”

“…It is then impossible to envisage any manipulation of the film during drying and furthermore it is necessary to have a sufficiently sensitive and fast weighing method to be able to monitor the evolution of the mass m(t) of the film with adequate accuracy. Several routes can be considered in this case: a high-precision gravimetric monitoring [55], thermogravimetric analysis (TGA) or differential scanning calorimetry (DSC) [57].…”

“…12 is therefore described well by an 1D isothermal (thin film, thus low Biot number and evaporative cooling neglected) evaporation-diffusion model. This model provides the spatio-temporal evolution of the mass concentration w c i (z, t) of each constituent (i) in the film [55] by solving the coupled equations of particle diffusion:…”

Patterning of a Drying Emulsion Film

“…Study of films is important for many different industrial domains such as coatings 1 , cosmetics 2 and micro-electronics 3 . Deposited materials are usually particle dispersions as in paints or emulsions as in cosmetics, enabling to meet requirements such as anti-corrosion 4 , color 5 , sensoriality 6 .…”

Isothermal dehydration of thin films

“…Polymeric formulations for cosmetics are an example of the former and plant and food systems of the latter [7][8][9]. Although the kinetics may involve different mechanisms, they share crucial key parameters such as the activity of water and its diffusivity through the matrix, the initial chemical composition having a strong impact on the morphology of the final dry product [10,11].…”