Reticulated foam is a veryporous, low-density solidfoam. 'Reticulated' means like anet. Reticulated foams are extremely open foams i.e. there are few, if any, intact bubbles or cell windows. In contrast, the foam formed bysoap bubbles is composed solely of intact (fully enclosed) bubbles. In a reticulated foam only the lineal boundaries where the bubbles meet (Plateau borders) remain.
The solid component of a reticulated foam may be anorganic polymer likepolyurethane, aceramic, or ametal. These materials are used in a wide range of applications where the high porosity and largesurface area are needed, includingfilters,catalyst supports,fuel tank inserts, andloudspeaker covers.
A description of the structure of reticulated foams is still being developed. WhilePlateau's laws, the rules governing the shape of soap films in foams were developed in the 19th century, a mathematical description of the structure is still debated. The computer-generatedWeaire–Phelan structure is the most recent. In a reticulated foam only theedges of thepolyhedra remain; thefaces are missing. In commercial reticulated foam, up to 98% of the faces are removed. Thedodecahedron is sometimes given as the basic unit for these foams,[1] but the most representative shape is a polyhedron with 13 faces.[2][3] Cell size and cell size distribution are critical parameters for most applications.Porosity is typically 95%, but can be as high as 98%.[4] Reticulation affects many of the physical properties of a foam. Typically resistance to compression is decreased while tensile properties like elongation and resistance to tearing are increased.[5]
Robert A. Volz is credited with discovering the first process for making reticulated polyurethane foam in 1956 while working for theScott Paper Company.[6] Production of reticulatedpolyurethane foam is a two-step process that begins with the creation of conventional (closed-cell) polyurethane foam, after which cell faces (or "windows") are removed. To do so, the fact that the higher surface area and lower mass of cell faces compared with cell struts (or edges) makes them much more susceptible to both combustion and chemical degradation is exploited. Thus, closed-cell foam is either filled with a combustible gas likehydrogen and ignited under controlled conditions, or it is exposed to asodium hydroxide solution to chemically degrade the foam, which will remove cell windows whilst sparing the edges.[7]
Reticulatedceramic foams are made by coating a reticulated polyurethane foam with an aqueous suspension of a ceramic powder then heating the material to first evaporate the water then fuse the ceramic particles and finally to burn off the organic polymer.[4]
Reticulatedmetal foam can also be made using polyurethane foam as a template similar to its use in ceramic foams. Metals can bevapor deposited onto the polyurethane foam and then the organic polymer burned off.[8]
Reticulated foams are used where porosity, surface area, and low density are important.
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