Formation of Perfluoropolyether Coatings by the Rapid Expansion of Supercritical Solutions (RESS) Process. Part 1:  Experimental Results

Abstract

The rapid expansion of supercritical solutions (RESS) process is a promising environmentally benign technology for fine droplet or particle formation. The absence of organic solvents and narrow size distribution of RESS precipitates make this process attractive for polymer coating applications. In our work, this technique has been used to produce droplets of perfluoropolyethers from CO2 solutions without the aid of cosolvents for the coating of porous materials applied in monumental and civil infrastructures. The present work is aimed at gaining an understanding of the relationship between droplet and spray characteristics and RESS process conditions. As such, a combined experimental/computational approach is applied to a representative binary system consisting of a low-molecular-weight perfluoropolyether diamide (PFD) dissolved in supercritical CO2. Part 1 of this work presents phase equilibria measurements and polymer droplet size characterizations under different operating conditions. The effects of temperature, solute concentration, and nozzle configuration on droplet and spray characterization and transfer efficiency are discussed. Part 2 of this work presents a multidimensional computational fluid dynamics model of the RESS expansion process and describes the use of the model in further analyzing and interpreting experimental data.

Porous Materials and Supercritical Fluids

“…[55] Broadly speaking, there are two main strategies to achieve this; rapid expansion of supercritical solutions [14,56,57] (where the material must be soluble in the fluid) and antisolvent precipitation [15,58,59] (where the material should be insoluble). Antisolvent precipitation has potential for generating porous microparticles from a wide variety of substrates, particularly since it does not require that the starting material is soluble in the SCF solvent (see also discussion on membranes, [46,47] Sec.…”

Polymeric Nanoparticles Preparation Techniques and Applications for Drug Delivery System- A Brief Review.

“…The high degree of super saturation, accompanied by the rapid pressure reduction in the expansion, results in homogenous nucleation and thereby, the formation of well-dispersed particles. Results from mechanistic studies of different model solutes for the RESS process indicate that both nanometer and micrometer-sized particles are present in the expansion jet 43 . A few studies were carried out on the production of PNPs using RESS.…”

Deagglomeration of nanoparticle aggregates via rapid expansion of supercritical or high‐pressure suspensions

“…Many experiments and two-dimensional simulations indicate that in a RESS process only about 50% of the mass would pass through the Mach disc. 44,45,51,54,61 To check the flow behavior in the free expansion zone, steady 2D (axisymmetric) computational fluid dynamics (CFD) simulations were performed using a commercial software Fluent V R . The results of these CFD simulations are presented in the Appendix A.…”