Chemistry:Foam

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Foam is a two-phase material system of gas cells enclosed by liquid or solid material, made by the dispersion of gas in non-gaseous material.[1]: 6 [2]: 4 [3] Foam "may contain more or less liquid [or solid] according to circumstances",[1]: 6  although in the case of gas-liquid foams, the gas occupies most of the volume.[2]: 4 

In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas.[4]

Etymology

The word derives from Old English fām, from Proto-Germanic faimaz, ultimately related to Sanskrit phéna.

Structure

File:Order and Chaos.tif One scale is the bubble: material foams are typically disordered and have a variety of bubble sizes.[5] The Weaire–Phelan structure is reported in one primary philosophical source to be the best possible (optimal) unit cell of a perfectly ordered foam,[6] while Plateau's laws describe how soap-films form structures in foams.[7]

Foams are examples of dispersed media. In general, gas is present, so it divides into gas bubbles of different sizes (i.e., the material is polydisperse)—separated by liquid regions that may form films, thinner and thinner when the liquid phase drains out of the system films.[8]Lua error: Internal error: The interpreter has terminated with signal "24". Solid foams are a class of lightweight cellular engineering materials. These foams are typically classified into two types based on their pore structure: open-cell-structured foams (also known as reticulated foams) and closed-cell foams. At high enough cell resolutions, any type can be treated as continuous or "continuum" materials and are referred to as cellular solids,[24] with predictable mechanical properties.

An open-cell metal foam

Open-cell foams can be used to filter air. For example, a foam embedded with catalyst has been shown to catalytically convert formaldehyde to benign substances when formaldehyde polluted air passes through the open cell structure.[25]

Open-cell-structured foams contain pores that are connected to each other and form an interconnected network that is relatively soft. Open-cell foams fill with whatever gas surrounds them. If filled with air, a relatively good insulator results, but, if the open cells fill with water, insulation properties would be reduced. Recent studies have put the focus on studying the properties of open-cell foams as an insulator material. Wheat gluten/TEOS biofoams have been produced, showing similar insulator properties as for those foams obtained from oil-based resources.[26] Foam rubber is a type of open-cell foam.

A closed-cell metal foam

Closed-cell foams do not have interconnected pores. The closed-cell foams normally have higher compressive strength due to their structures. However, closed-cell foams are also, in general more dense, require more material, and as a consequence are more expensive to produce. The closed cells can be filled with a specialized gas to provide improved insulation. The closed-cell structure foams have higher dimensional stability, low moisture absorption coefficients, and higher strength compared to open-cell-structured foams. All types of foam are widely used as core material in sandwich-structured composite materials.

The earliest known engineering use of cellular solids is with wood, which in its dry form is a closed-cell foam composed of lignin, cellulose, and air. From the early 20th century, various types of specially manufactured solid foams came into use. The low density of these foams makes them excellent as thermal insulators and flotation devices and their lightness and compressibility make them ideal as packing materials and stuffings.

An example of the use of azodicarbonamide[27] as a blowing agent is found in the manufacture of vinyl (PVC) and EVA-PE foams, where it plays a role in the formation of air bubbles by breaking down into gas at high temperature.[28][29][30]

The random or "stochastic" geometry of these foams makes them good for energy absorption, as well. In the late 20th century to early 21st century, new manufacturing techniques have allowed for geometry that results in excellent strength and stiffness per weight. These new materials are typically referred to as engineered cellular solids.[24]

Syntactic foam

Integral skin foam

Integral skin foam, also known as self-skin foam, is a type of foam with a high-density skin and a low-density core. It can be formed in an open-mold process or a closed-mold process. In the open-mold process, two reactive components are mixed and poured into an open mold. The mold is then closed and the mixture is allowed to expand and cure. Examples of items produced using this process are arm rests, baby seats, shoe soles, and mattresses. The closed-mold process, more commonly known as reaction injection molding (RIM), injects the mixed components into a closed mold under high pressures.[31]

  • Micrograph of temper (memory) foam
    Micrograph of temper (memory) foam
  • Silicone foam penetration seal Lua error: Internal error: The interpreter has terminated with signal "24".
    Silicone foam penetration seal Lua error: Internal error: The interpreter has terminated with signal "24".
  • Industrial CT scanning of a foam ball Lua error: Internal error: The interpreter has terminated with signal "24".
    Industrial CT scanning of a foam ball Lua error: Internal error: The interpreter has terminated with signal "24".
  • Polystyrene foam cushioning
    Polystyrene foam cushioning
  • Foamed aluminum Lua error: Internal error: The interpreter has terminated with signal "24".
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Foam scales and properties

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See also

References

  1. ↑ 1.0 1.1 1.2 1.3 Weaire, D.L.; Hutzler, Stefan (1999). The Physics of Foams. Oxford, England: Oxford University Press. ISBN 0198510977. https://books.google.com/books?id=mEHlZ9ZodFsC. Retrieved 30 August 2024.  Note, this source focuses only on liquid foams.
  2. ↑ 2.0 2.1 Cantat, I; Cohen-Addad, S; Elias, F; Graner, F; Höhler, R; Pitois, O; Rouyer, F & Saint-Jalmes, A (2013). Foams: Structure and Dynamics. Oxford, England: Oxford University Press. ISBN 978-0199662890. https://books.google.com/books?id=Ndzzl1hUNRoC. Retrieved 30 August 2024.  Note, this source also focuses on liquid foams.
  3. ↑ The general use of the term, which includes both noun and verb forms, is both narrower and broader than the one from material science described here. In general use, it is narrower, in that it most often refers to liquid foams; it is broader in that it includes all manners of such, and the actions to produce them, hence, according to Merriam-Webster, the term refers to "a light frothy mass of fine bubbles formed in or on the surface of a liquid or from a liquid", giving the examples of those produced by "salivating or sweating", ones stably produced to fight fires, ones that are the product of gas bubbles introduced during manufacturing, and then the further broad examples of sea foam, and then anything resembling the foregoing. Finally, the general definition includes actions to produce all of the above. See "Foam". Merriam-Webster. https://www.merriam-webster.com/dictionary/foam. 
  4. ↑ "Foam Explained" (in en-US). https://accushapediecutting.com/foam-explained. 
  5. ↑ "Particle-stabilized foams", Bubble and Foam Chemistry (Cambridge University Press): pp. 269–306, 2016-07-31, doi:10.1017/cbo9781316106938.009, ISBN 978-1-107-09057-6, https://doi.org/10.1017/cbo9781316106938.009, retrieved 2025-05-24 
  6. ↑ Morgan, F. (2008). "Existence of Least-perimeter Partitions". Philosophical Magazine Letters 88 (9–10): 647–650. doi:10.1080/09500830801992849. Bibcode: 2008PMagL..88..647M. 
  7. ↑ Ball, Philip (2008-01-18). "The maths behind group showers". Nature. doi:10.1038/news.2007.352. ISSN 0028-0836. https://doi.org/10.1038/news.2007.352. 
  8. ↑ Lucassen, J. (1981). Lucassen-Reijnders, E. H.. ed. Anionic Surfactants – Physical Chemistry of Surfactant Action. NY, USA: Marcel Dekker. 
  9. ↑ 9.0 9.1 Bikerman, J.J. "Formation and Structure" in Foams New York, Springer-Verlag, 1973. ch 2. sec 24–25
  10. ↑ "The Foam". IHC News. January 2009. http://www.clariant.com/C12575E4001FB2B8/vwLookupDownloads/2009_01_IHC_Newsletter_Defoaming.pdf/$FILE/2009_01_IHC_Newsletter_Defoaming.pdf. 
  11. ↑ Stevenson, Paul (3 January 2012). Foam Engineering: Fundamentals and Applications. John Wiley & Sons. ISBN 9781119961093. https://books.google.com/books?id=FXAM3eBpZ0kC&dq=info:LfvRsPG2-6QJ:scholar.google.com/&pg=PT10. 
  12. ↑ Wilson, A.J, "Principles of Foam Formation and Stability." Foams: Physics, Chemistry, and Structure. New York, Springer-Verlag, 1989, ch 1
  13. ↑ Queheillalt, Douglas T.; Wadley, Haydn N.G. (January 2005). "Cellular metal lattices with hollow trusses". Acta Materialia 53 (2): 303–313. doi:10.1016/j.actamat.2004.09.024. Bibcode: 2005AcMat..53..303Q. 
  14. ↑ Kooistra, Gregory W.; Deshpande, Vikram S.; Wadley, Haydn N.G. (August 2004). "Compressive behavior of age hardenable tetrahedral lattice truss structures made from aluminium". Acta Materialia 52 (14): 4229–4237. doi:10.1016/j.actamat.2004.05.039. Bibcode: 2004AcMat..52.4229K. 
  15. ↑ 15.0 15.1 Courtney, Thomas H. (2005) (in English). Mechanical Behavior of Materials. Waveland Press, Inc. pp. 686–713. ISBN 1-57766-425-6. 
  16. ↑ Liu, Mingchao; Wu, Jian; Gan, Yixiang; Hanaor, Dorian; Chen, C. Q. (2019). "Multiscale modeling of effective elastic properties of fluid-filled porous materials". International Journal of Solids and Structures 162: 36–44. doi:10.1016/j.ijsolstr.2018.11.028. https://hal.science/hal-02344039. 
  17. ↑ Ashby, M. F. (1983). "The Mechanical Properties of Cellular Solids". Metallurgical Transactions 14A (9): 1755–1769. doi:10.1007/bf02645546. Bibcode: 1983MTA....14.1755A. https://doi.org/10.1007/bf02645546. 
  18. ↑ Li, Pei; Guo, Y. B.; Shim, V. P. W. (2020). "A rate-sensitive constitutive model for anisotropic cellular materials - Application to a transversely isotropic polyurethane foam". International Journal of Solids and Structures 206: 43–58. doi:10.1016/j.ijsolstr.2020.08.007. https://doi.org/10.1016/j.ijsolstr.2020.08.007. 
  19. ↑ Yu, Y. J.; Hearon, K.; Wilson, T. S.; Maitland, D. J. (2011). "The effect of moisture absorption on thephysical properties of polyurethane shapememory polymer foams". Smart Materials and Structures 20 (8). doi:10.1088/0964-1726/20/8/085010. PMID 21949469. PMC 3176498. Bibcode: 2011SMaS...20h5010Y. http://dx.doi.org/10.1088/0964-1726/20/8/085010. 
  20. ↑ IUPAC (1997). "Emulsion". Compendium of Chemical Terminology (The "Gold Book"). Oxford: Blackwell Scientific Publications. doi:10.1351/goldbook.E02065. ISBN 978-0-9678550-9-7. http://goldbook.iupac.org/E02065.html. 
  21. ↑ Crystal (2023-08-14). "The Science Behind Natural Soaps' Bubbles" (in en-US). https://thefreckledfarmsoapcompany.com/blog/the-science-behind-natural-soaps-bubbles/. 
  22. ↑ The open structure of an over-risen dough is easy to observe; instead of consisting of discrete gas bubbles, the dough consists of a gas space filled with threads of the flour-water paste.Lua error: Internal error: The interpreter has terminated with signal "24".Lua error: Internal error: The interpreter has terminated with signal "24".
  23. ↑ Wang, Shuo; Austin, Peter; Chakrabati-Bell, Sumana (2011). "It's a maze: The pore structure of bread crumbs". Journal of Cereal Science 54 (2): 203–210. doi:10.1016/j.jcs.2011.05.004. 
  24. ↑ 24.0 24.1 Gibson, Ashby (1999). Cellular Solids: Structure and Properties. Cambridge, UK: Cambridge University Press. ISBN 9781316025420. 
  25. ↑ Carroll, Gregory T.; Kirschman, David L. (2023-01-23). "Catalytic Surgical Smoke Filtration Unit Reduces Formaldehyde Levels in a Simulated Operating Room Environment" (in en). ACS Chemical Health & Safety 30 (1): 21–28. doi:10.1021/acs.chas.2c00071. ISSN 1871-5532. https://pubs.acs.org/doi/10.1021/acs.chas.2c00071. 
  26. ↑ Wu, Qiong; Andersson, Richard L.; Holgate, Tim; Johansson, Eva; Gedde, Ulf W.; Olsson, Richard T.; Hedenqvist, Mikael S. (2014). "Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica". Journal of Materials Chemistry A 2 (48): 20996–21009. doi:10.1039/C4TA04787G. 
  27. ↑ Reyes-Labarta, J.A.; Marcilla, A. (2008). "Kinetic Study of the Decompositions Involved in the Thermal Degradation of Commercial Azodicarbonamide". Journal of Applied Polymer Science 107 (1): 339–346. doi:10.1002/app.26922. Bibcode: 2008JAPS..107..339R. 
  28. ↑ Reyes-Labarta, J.A.; Marcilla, A. (2012). "Thermal Treatment and Degradation of Crosslinked Ethylene Vinyl Acetate-Polyethylene-Azodicarbonamide-ZnO Foams. Complete Kinetic Modelling and Analysis". Industrial & Engineering Chemistry Research 51 (28): 9515–9530. doi:10.1021/ie3006935. 
  29. ↑ Reyes-Labarta, J.A.; Marcilla, A. (2008). "Differential Scanning Calorimetry Analysis of the Thermal Treatment of Ternary Mixtures of Ethylene Vinyl Acetate, Polyethylene and Azodicarbonamide". Journal of Applied Polymer Science 110 (5): 3217–3224. doi:10.1002/app.28802. Bibcode: 2008JAPS..110.3217R. 
  30. ↑ Reyes-Labarta, J.A.; Olaya, M.M.; Marcilla, A. (2006). "DSC Study of the Transitions Involved in the Thermal Treatment of Foamable Mixtures of PE and EVA Copolymer with Azodicarbonamide". Journal of Applied Polymer Science 102 (3): 2015–2025. doi:10.1002/app.23969. 
  31. ↑ Ashida, Kaneyoshi (2006). Polyurethane and related foams: chemistry and technology. CRC Press. pp. 79–81. ISBN 978-1-58716-159-9. https://books.google.com/books?id=IQUd-3aKSD4C. 

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Further reading

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