Reticulated foam is a very

porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

, low density solid

foam Foams are materials formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the ...

. 'Reticulated' means like a net. Reticulated foams are extremely open foams i.e. there are few, if any, intact bubbles or cell windows. In contrast, the foam formed by

soap bubbles A soap bubble is an extremely thin film of soap or detergent and water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact ...

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 an organic polymer like

polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced fro ...

, a

ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

or a

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typica ...

. These materials are used in a wide range of applications where the high porosity and large

surface area The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of ar ...

are needed, including

filters Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component th ...

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recy ...

supports,

fuel tank A fuel tank (also called a petrol tank or gas tank) is a safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propell ...

inserts, and

loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or "l ...

covers.

Structure and properties

A description of the structure of reticulated foams is still being developed. While

Plateau's laws Plateau's laws describe the structure of soap films. These laws were formulated in the 19th century by the Belgian physicist Joseph Plateau from his experimental observations. Many patterns in nature are based on foams obeying these laws. 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-generated Weaire–Phelan structure is the most recent. In a reticulated foam only the edges of the

polyhedra In geometry, a polyhedron (plural polyhedra or polyhedrons; ) is a three-dimensional shape with flat polygonal faces, straight edges and sharp corners or vertices. A convex polyhedron is the convex hull of finitely many points, not all on ...

remain; the faces are missing. In commercial reticulated foam, up to 98% of the faces are removed. The

dodecahedron In geometry, a dodecahedron (Greek , from ''dōdeka'' "twelve" + ''hédra'' "base", "seat" or "face") or duodecahedron is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron with regular pentago ...

is sometimes given as the basic unit for these foams, but the most representative shape is a polyhedron with 13 faces. Cell size and cell size distribution are critical parameters for most applications.

Porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

is typically 95%, but can be as high as 98%. 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.

Production

Robert A. Volz is credited with discovering the first process for making reticulated polyurethane foam in 1956 while working for the

Scott Paper Company The Scott Paper Company was the world's largest manufacturer and marketer of sanitary tissue products with operations in 22 countries. Its products were sold under a variety of well-known brand names, including ''Scott Tissue'', '' Cottonelle'', ...

. Production of reticulated

polyurethane foam Polyurethane products have many uses. Over three quarters of the global consumption of polyurethane products is in the form of foams, with flexible and rigid types being roughly equal in market size. In both cases, the foam is usually behind oth ...

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 like

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxi ...

and ignited under controlled conditions, or it is exposed to a

sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and a ...

solution to chemically degrade the foam, which will remove cell windows whilst sparing the edges. Reticulated

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. Reticulated

foam can also be made using polyurethane foam as a template similar to its use in ceramic foams. Metals can be vapor deposited onto the polyurethane foam and then the organic polymer burned off.

Applications

Reticulated foams are used where porosity, surface area, low density are important. * Puppets (such as the bodies/faces/hands of

The Muppets The Muppets are an American ensemble cast of puppet characters known for an absurdist, burlesque, and self-referential style of variety-sketch comedy. Created by Jim Henson in 1955, they are the focus of a media franchise that encompasses tel ...

) *

Humidifier A humidifier is a device, primarily an electrical appliance, that increases humidity (moisture) in a single room or an entire building. In the home, point-of-use humidifiers are commonly used to humidify a single room, while whole-house or furn ...

pads *

Air conditioner Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...

filters * Scrubbers * Ceramic filters for filtering molten metal * Vehicle and bacteria filters * Speaker grills * Face mask and pads * Outdoor cushions * Marine seating *

Shoe polish Shoe polish (or boot polish) is a waxy paste, cream, or liquid that is used to polish, shine, and waterproof leather shoes or boots to extend the footwear's life and restore its appearance. Shoe polishes are distinguished by their textures ...

and cosmetic applicators * Ink jet cartridges *

Aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...

(water purification) * Anti-slosh filling in fuel tanks for aircraft (such as the

A-10 Thunderbolt II The Fairchild Republic A-10 Thunderbolt II is a single-seat, twin-turbofan, straight-wing, subsonic attack aircraft developed by Fairchild Republic for the United States Air Force (USAF). In service since 1976, it is named for the Republic ...

) and race cars

References

External links

Reticulation Process, FXI
{{Webarchive, url=https://web.archive.org/web/20150301215236/http://fxi.com/foam-technologies/processes/reticulation.php , date=2015-03-01 Polyurethanes Plastics Ceramic materials Foams Materials science