Droplet Membrane

Relationships between emulsion droplet membrane thickness and iron-promoted lipid oxidation... 

Keywords Self-cleaning mechanism, contact angle, static wetting, nonlinear finite element analysis, droplet membranes. 

This paper is organized as follows Section 5.2 provides a brief overview on the basic definitions used in differential geometry, on which the droplet membrane model is based. Then the model describing a self-cleaning system is illustrated in Section 5.3, where the following individual sub-models are introduced the droplet model, the substrate surface model, and the model discussing the particle-droplet interaction. The governing equations of these models are presented in Section 5.4, followed by the force analysis for the last model performed in Section 5.5. Numerical examples are shown in Section 5.6 in order to clarify the theory. In the end, we outline the summary of the presented work in Section 5.7. 

Figure 5.2 Self-cleaning system model comprising droplet membrane model, substrate surface model, and particle-droplet interaction model.

A second form of desolvation chamber relies on diffusion of small vapor molecules through pores in a Teflon membrane in preference to the much larger droplets (molecular agglomerations), which are held back. These devices have proved popular with thermospray and ultrasonic nebulizers, both of which produce large quantities of solvent and droplets in a short space of time. Bundles of heated hollow polyimide or Naflon fibers have been introduced as short, high-surface-area membranes for efficient desolvation. 

Phase Inversion (Solution Precipitation). Phase inversion, also known as solution precipitation or polymer precipitation, is the most important asymmetric membrane preparation method. In this process, a clear polymer solution is precipitated into two phases a soHd polymer-rich phase that forms the matrix of the membrane, and a Hquid polymer-poor phase that forms the membrane pores. If precipitation is rapid, the pore-forming Hquid droplets tend to be small and the membranes formed are markedly asymmetric. If precipitation is slow, the pore-forming Hquid droplets tend to agglomerate while the casting solution is stiU fluid, so that the final pores are relatively large and the membrane stmcture is more symmetrical. Polymer precipitation from a solution can be achieved in several ways, such as cooling, solvent evaporation, precipitation by immersion in water, or imbibition of... 

In the suspension polymerization of PVC, droplets of monomer 30—150 p.m in diameter are dispersed in water by agitation. A thin membrane is formed at the water—monomer interface by dispersants such as poly(vinyl alcohol) or methyl cellulose. This membrane, isolated by dissolving the PVC in tetrahydrofuran and measured at 0.01—0.02-p.m thick, has been found to be a graft copolymer of polyvinyl chloride and poly(vinyl alcohol) (4,5). Early in the polymerization, particles of PVC deposit onto the membrane from both the monomer and the water sides, forming a skin 0.5—5-p.m thick that can be observed on grains sectioned after polymerization (4,6). Primary particles, 1 p.m in diameter, deposit onto the membrane from the monomer side (Pig. 1), whereas water-phase polymer, 0.1 p.m in diameter, deposits onto the skin from the water side of the membrane (Pig. 2) (4). These domain-sized water-phase particles may be one source of the observed domain stmcture (7). 

L. Golubovie. Passages and droplets in lamellar fluid membrane phases. Phys 50 R2419-R2422, 1994. 

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