A Multifaceted Foam

You can find reticulated polyurethane foam in products from appliances to air filters to inkjet printers. Read how and why this versatile material can be used in a host of designs.

By Michael C. Curti

Reticulated polyurethane foam is a versatile material that can be fabricated or combined with other materials into virtually any configuration. It is used on, in, or around products serving consumers, business, industry, health care, research, and the military.

How does polyurethane foam become reticulated? It is subjected to a proprietary process inside a specially designed vessel using heat and pressure to create flexible skeletal foam structures without cell membranes.

The resulting open-pore foam can then be produced in a range of precisely controlled pore sizes which contain void volumes of up to 98 percent and surface areas up to 200 ft^.2 per cubic foot. The benefit? Various pore sizes, typically from 4 through 100 pores per inch, enable the material's use in specific applications; they also help control permeability and add design flexibility and a pleasing aesthetic appearance.

Among the benefits of reticulated polyurethane foam are easy fabrication and chemical resistance. It also exhibits high tensile, elongation, and tear properties which allow such fabrication techniques as cutting, shaping, stapling, tacking, stitching, cementing, laminating, and grommeting. The foam also is impervious (non-nutrient) to microbial organisms and some materials are available with permanent fungicidal/bactericidal additives for enhanced antimicrobial activity. It can be supplied in buns, sheets, rolls, die-cuts, and complex compound shapes.

Application Notes
There are myriad applications for reticulated polyuerethane foam. Some are more familiar than others, such as for shoe polish and cosmetic applicators, speak grilles, mops, odorizer wicks, air condition filters, and sponges. In industrial tasks, the strong, easily fabricated, and chemical resistant nature of reticulated polyurethane foam allows it to be used for filtering, protecting, sealing, sound absorption/vibration dampening, wiping, and other specialized processs.

In metal casting, the material is used in the production of ceramic filters to eliminate impurities in the metal casting process. It functions as a sacrificial catalytic substrate which is first coated with a ceramic slurry and then baked to remove the foam and fuse the ceramic, creating a rigid ceramic part that provides rigorous paths to remove impurities when molten metal is poured through it during the casting process.

In addition, hydraulic and pneumatic systems use it to eleiminate impurities in air or fluid lines, valves, and other components. It is also usedfor filtering air in humidifiers, bactteria filters, vehicle air cleaners, and engine inlet prefilters.

Reticulated polyurethane foam is used extensively to enhance safety in military aircraft, land vehicles, and marine vessels. It can be found in fuel tanks of military fighter aircraft as well as C-130 and P-3 transport/reconnaissance aircraft where it prevents catatrophic explosions in case of hostile incendiary arms fire or when over-the-wing refueling creates a static spark that can ignite fuel vapor. It's even used in race car fuel tanks for added safety to prevent explosions if a crash occurs.

The Compression Dimension
Changing the state of reticulated polyurethane foam opens up other applications as well. When it is compressed, the foam exhibits other properties. These include high void volumes (up to 95 percent) and uniform porosity; non-directional characteristics and uniform texture (suitable for ink rollers); non-linting superior filtration qualities to impart a rigorous flow path and more impingement surfaces to trap particulate matter; and exceptional breathability, wicking, capillary action, and high strength.

Because compression ratios are as high as 20:1, the foam can be used for many filtering, reservoiring, and wicking/absorption applications.