Semirigid foams

Polyurethanes. About 3% of the U.S. polyurethanes market in 1988 was derived from the condensation product of polyisocyanates with low molecular weight polyadipates having hydroxyl end groups (195). In 1986 this amounted to 29,000 t, or 4% of total adipic acid consumption. The percentage was similar in Western Europe. About 90% of these adipic acid containing polyurethanes are used in flexible or semirigid foams and elastomers, with the remainder used in adhesives, coatings, and spandex fibers. 

Textile uses are a relatively stable area and consist of the lamination of polyester foams to textile products, usually by flame lamination or electronic heat sealing techniques. Flexible or semirigid foams are used in engineered packaging in the form of special slab material. Flexible foams are also used to make filters (reticulated foam), sponges, scmbbers, fabric softener carriers, squeegees, paint appHcators, and directly appHed foam carpet backing. 

Semicrystalline partial aromatic polyamides, 139 Semicrystalline polyesters, 45 Semicrystalline polymers, melting temperatures of, 33 Semirigid foams, 203 tests for, 244 Sensitization, 246... 

Semi-rigid foams take much longer to return to their original dimensions after deformation than flexible foams. They offer exceptional shock absorbance, which suits them for many protective applications, especially in automobiles. In general, we use polyester diols in semirigid foams because of their superior mechanical properties. 

Semireinforcing blacks, 21 776 Semirigid foams, 25 470 Semirigid food packaging, 18 47-51 Semisolid drug dosage forms, 18 713 Semisolid resins, 10 372 Semisweet chocolate, 6 362 Semisynthetic 14-membered macrolides, 15 280-287... 

Rigid foam PS, PU, and phenolic resin, and the semirigid foam of PE were examined with regard to their mechanical properties. The effects of preloading the foams on their mechanical properties are discussed. 

Special paints are used for protecting flammable substrates by retarding flame spread. Such paints contain polyammonium phosphate, which emits a gas at elevated temperatures but lower than charring temperatures. The vehicle softens and is foamed by the gas forming a semirigid foamed char on the surface, which insulates the substrate from further heat. 

MII C-23806A(2)(EC) Cable, Radio Frequency, Coaxial, Semirigid, Foam Dielectric, General Specification, 4 April 1984, 1 p amend + 10 pp base spec (FSC 6145) (EC)... 

Carwinate []. TM for isocyanates used to make urethane elastomers, coatings, foam adhesives, rigid plastics, sealants, and one-shot flexible, semiflexible, and semirigid foams. 

These good recovery properties are the reason why the preferred term is semiflexible foams and not semirigid foams. 

Bayfill . [Bayer Miles] Polyurethane, semirigid foam (RIM). 

Polyurethane, a semirigid foam, was selected to transfer load from the artifact inner surface to the internal skeleton, which is to be linked directly to the rigid external brace. 

Copolymers of styrene and other monomers are also used in packaging foams. The most common is styrene-acrylonitrile (SAN) foam, which is a semirigid foam and offers better performance than PS foam in repeated drops and for heavy products (high static loads). The density of SAN foam is usually about 16 Ib/m (1 Ib/ft ). 

Many tests commonly applied to plastics in the form of solids, elastomers, coatings, and sealants may of course also be applied to cellular plastics. For example, notched impact strength tests can be applied to high-density structural foams, and it is very common to quote Shore hardness values for skin hardnesses of rigid and semirigid foam moldings. It is the intention here, however, to restrict the discussion to tests derived exclusively for plastics containing a cellular structure. 

Semirigid foam is usually tested using methods normally applied to rigid or flexible foams. In some instances they are tested for ultimate elongation (as a percentage to BS903. Part A2 [74]). The surface hardne.ss is also important in. some molded part applications, and that property can be measured using standard Shore A hardness procedures. 

Flexible plastic foams may be found in the form of very soft cushioning materials used in upholstery, clothing interlayers, automobile seats, vibration absorbers, etc. The most common flexible foam resins are polyurethanes, foamed vinyls, cellular polyethylene, cross-linked polyethylene, and silicone foam. Semirigid foams are used for floatation devices, marine bumpers, special electrical insulation on television cables, packaging, and a host of other applications. Rigid foams are used in the production of airplane parts, boats, electronic encapsulation, and many furniture applications where wood was formerly used. 

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