Multicellular foam

Unicellular foams are used for insulation, buoyancy, and flotation applications, while multicellular foams are used for upholstery, carpet backing, and laminated textiles. Expanded PS (Styrofoam), which is produced by the extrusion of PS beads containing a volatile liquid, is used to produce low-density moldings such as foamed drinking cups and insulation boards. Foamed products are also produced from PVC, LDPE, urea resins, ABS, and PU. PU foams are versatile materials, which range from hard (rigid) to soft (flexible). These are produced by the reaction of a polyol and a diisocyanate. 

As the reaction nears completion, gelation and finally solidification occurs. This solid is in the form of multicellular foam. 

These coatings bubble and foam to form a thermal insulation when subjected to a fire. They have been used for many decades. Such coatings cannot be differentiated from conventional coatings prior to the occurrence of a fire situation. Thereupon, however, they decompose to form a thick, nonflammable, multicellular, insulative barrier over the surface on which they are applied. This insulative foam is a very effective insulation that maintains the temperature of a flammable or heat distortable substrate below its ignition or distortion point. It also restricts the flow of air (oxygen) to fuel the substrate. 

Until 1920, the only flexible foam available was the natural sponge, but chemically foamed rubber and mechanically foamed rubber latex were introduced before World War II. These foams may consist of discrete unit cells (unicellular, closed cell), or they may be composed of interconnecting cells (multicellular, open cells) depending on the viscosity of the system at the time the blowing agent is introduced. Over 1.5 million tons of foamed plastic is produced annually in the United States. 

Unicellular (closed cell, discrete unit cells) and multicellular (open cells, interconnecting cells) foams are made through the chemical and physical introduction of gasses. 

Which foam is preferable for upholstery (a) unicellular or (b) multicellular ... 

Matsushita, T., Ijima. H., Koide, N., Funatsu, K., High albumin production by multicellular spheroids of adull rat hepatocytes formed in the pores of polyurethane foam. Appl. Microbiol. Biotechnol. 1991. vol. 36. no. 3. pp. 324-326. 

Jahjah [the prior art reference cited by the USPTO] combines the preformed foam into various cement and concrete mixtures wherein known aggregates may optionally be incorporated. The foam is introduced from a reservoir into a concrete mixer containing the cement mix, and, in our opinion, it would be obvious to a technician having ordinary skill in the art to add the foam gradually to the cement mix while it was being mixed, since, as pointed out by the Examiner, conventional cement mixers operate in this fashion. Further, Jahjah obtains uniform dispersion of the foam and produces a multicellular cementitious product not differentiated in this record from that obtained by appellant. 

The application of a blowing agent is one method of producing a foam structure, that is, one in which a polymer matrix contains gas-filled cells. Chemically foamed rubbers and plastics were first introduced in the late 1930s. Foams consist of either discrete unit cells (unicellular) or interconnecting cells (multicellular) depending on the viscosity of the polymer. Unicellular foams are used in... 

Another approach involves intumescence. On heating, intumescent systems give rise to a swollen multicellular char capable of protecting the underlying material from the action of the flame (116). A common compound utilized for producing this foamed state is ammonium polyphosphate. 

Intumescent fire retardant additives undergo a thermal degradation process on heating, which produces a thermally stable, foamed, multicellular residue called intumescent char. When these substances are added to a polymeric material which is later involved in a fire, they produce an intumescent char which accumulates on the surface, while the polymer is consumed, providing insulation to the underling materials and partially protecting it from the action of the flame. 

Gelation and solidification take place, leaving a multicellular charred solid foam. 

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