Fluorocarbon vapors slow down coalescence in foams: influence of surfactant concentration

Steck, Katja; Dijoux, Jonathan; Preisig, Natalie; Bouylout, Victor; Stubenrauch, Cosima; Drenckhan, Wiebke

doi:10.1007/s00396-023-05129-7

Cited by 4 publications

(1 citation statement)

References 44 publications

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“…In fact, the same behavior is known for similar fullyuorinated hydrocarbons such as per uorohexane 28,29 . For instance, it could be shown that, due to their very low surface energies, FCs adsorb at gas/liquid interfaces in aqueous systems altering the packing of other species present at the surface [29][30][31][32][33] . In this context, investigating in more detail if and how exactly the FC interacts with the silicone surfactant molecules at gas/liquid interfaces in PUR foam systems would de nitely be an interesting study.…”

Section: Surface Tension Measurementsmentioning

confidence: 99%

Fluorocarbon-driven pore size reduction in polyurethane foams: an effect of improved bubble entrainment

Hamann,

Cotte-Carluer,

Andrieux

et al. 2023

Colloid Polym Sci

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Polyurethane (PU) foams are created via the chemical reactions arising after the blending of two initially liquid components (polyols and isocyanates). They are widely used for thermal insulation, for which a small pore size is required. Some of the most e cient pore size-reducing agents have proven to be perand poly uorinated carbons (FCs) which are simply added in small quantities to the initially liquid mixture. However, despite their long-standing use, their modes of action have only recently begun to be studied in detail. One widely accepted explanation of their action is that they supposedly suppress diffusional gas exchange between bubbles in the liquid-foam-state of the nascent PU foam (foam coarsening). However, using a new double-syringe mixing technique, we show that FCs act at a much earlier state of the process: they facilitate the entrainment of tiny air bubbles into PU foam systems during the initial blending processing. These bubbles serve as sites for heterogeneous nucleation during the foaming process, and their large number leads to a signi cant reduction of the characteristic pore size. More importantly, we also demonstrate that the same overall relation is found between the air bubble density and the nal pore size for systems with-and without FC. Combined with a detailed analysis of the pore size distribution, we argue that the main pore size reducing effect of FCs is to facilitate air entrainment and that foam aging-related effects only play a minor role.

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