Unicellular 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. 

Syntactic Foam. Hollow glass, ceramic, or plastic spheres are dispersed in the reactive liquid system before it is cast. When the liquid is polymerized and cured, the hollow spheres make it a unicellular foam. The air bubbles in the cells make it low-density, low dielectric constant and loss, and very resistant to compressive forces such as hydrostatic head in deep-sea equipment. 

Low-density unicellular foam made from this pressure process is available in a range of densities and hardnesses in various sizes ready for fabrication into the final product. Slab stock is used to produce shockabsorbing, flotation, and insulating foams. Typical densities range from 7 Ib/ft for shock-absorbing foams, 4 Ib/ft for flotation foams, and 6 Ib/ft for insulation foams. It is also possible to produce pressure-molded foams in cylindrical and ring-shaped molds (24) (3). 

The most Important distinction is between closed- and open-cell foams. In closed-cell (unicellular) foams, each gas bubble is separated from the others by thin walls of polymer these foams are optimal for flotation applications, structural rigidity, and thermal insulation. In open-cell foams, the cells are all interconnecting, and fluids and especially air can flow freely through the foam structure these are optimal for sponge products and for soft flexible materials. In the extreme case, when the last few remaining cell walls (windows) have been chemically dissolved out of an open-cell foam, it is sometimes called "reticulated."... 

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... 

Benzenesulfonylhydrazide [4,4 -oxybis (benzenesulfonylhydrazide), OBSH] n. A blowing agent, a white crystalline solid that melts and begins to decompose near 105°C. It produces a white unicellular foam when incorporated in PVC plastisol but has a strong residual odor that does not evolve when it is used in rubbers. It is also used in epoxy and phenolic foams and... 

Closed-cell foamed plastic (unicellular foam) n. A cellular plastic in, which interconnecting cells are too few to permit the bulk flow of fluids through the mass. 

Closed-cell, or unicellular, foams are those in which the greatest proportion of cells are not connected together by open passageways. Such a material only absorbs water or other liquid on the outermost surface cells. Closed-cell foams do not make effective sound-absorbing materials. Therefore, closed-cell foams are used for flotation devices and similar items. Open-cell, or interconnecting-cell, foam is a foam in which the greatest proportion of cells are connected by open passageways to other cells. Such a foam will absorb water when placed under water. 

MIL-P-9969 Polyurethane, Rigid, unicellular, Foam-In-Place for packaging... 

What are they like to eat Humans are particular about the organoleptic properties of their food. Microbial cells may have little taste or smell, or even smell or taste unpleasantly to some people. The texture may not be the same as in conventional foods, particularly with unicellular organisms. These draw-backs can be overcome by adding a proportion of SCP to manufactured foods. However, even when SCP is incorporated into manufactured foods it may not have suitable characteristics such as stability, ability to bind water or fats, or ability to form gels, emulsions or foams. SCP for feed does not have to meet such strict requirements. 

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 ... 

Federal Specification PP-C-1797A, "Cushioning Material, Resilient, Low Density, Unicellular, Polypropylene Foam," 1 September 1982. This specification supersedes the earlier Military Specification M1L-C-81823(AS) (1971). 

This specification covers chemically expanded unicellular elastomeric plastic foam for thermal insulation. It is used as the inherently buoyant foam in MII I 18045F. Has a Qualified Products Ust (QPL). 

This Navy specification covers a single class of foam, nominal density 2.0 Ib/ft rigid unicellular polyurethane foam, and the materials required for preparation by the foam-in-place technique. Requirements cover density, compressive strength, volume change after heat aging, humidity aging, compressive set, unicellularity (% open cells, max.), oil resistance, and fire resistance. 

This family of German hedgehog dolls , dating from the 1960s, is constructed from unicellular polyurethane foam which allows them to be flexible while keeping their shape. 

Unicellular plastic iyu-ni- sel-y3-br-. A term that has sometimes been used for closed-cell foamed plastic. 

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