Flexible urethane foams

Classification. Flexibie urethane foams have the largest market of all polyurethane products. The production properties and applications of various flexible urethane foams are described in the following sections. Flexible urethane foams are defined as open-cell urethane foams having the property of complete recovery immediately after compression. They can be classified into two kinds, i.e., polyether foams and polyester foams. Polyether foams are further classified as follows conventional flexible foams, high-resilience flexible foams (HR foams), cold-molded foams, super-soft foams, and viscoelastic foams. 

Semi-flexible foams (or semi-rigid foams) are sometimes classified as subdivisions of flexible foam because the foams have higher load-bearing properties and good compression recovery. Microcellular flexible foams and integral-skin flexible foams may also be classified in this category. In some classifications, however, microcellular foams are classified as elastomers. 

Different foams can be prepared by the proper choice of polyols, which will be described later. Polyisocyanates are used as joining agents 

Flexible urethane foams include slabstock foam, molded foam, and pour-in-place foam. In some cases, the latter two foams can be called flexible RIM foams (RIM is an abbreviation for reaction injection molding). 

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Antagonism between antimony oxide and phosphoms flame retardants has been reported in several polymer systems, and has been explained on the basis of phosphoms interfering with the formation or volatilization of antimony haUdes, perhaps by forming antimony phosphate (12,13). This phenomenon is also not universal, and depends on the relative amounts of antimony and phosphoms. Some useful commercial poly(vinyl chloride) (PVC) formulations have been described for antimony oxide and triaryl phosphates (42). Combinations of antimony oxide, halogen compounds, and phosphates have also been found useful in commercial flexible urethane foams (43). 

Oligomeric 2-ChloroethylPhosphate. Akzo s Fyrol 99 [109640-81-5] is produced either by self-condensation of tris(2-chloroethyl) phosphate (82) or by insertion of phosphoms pentoxide into this phosphate (82) followed by ethoxylation. It is low in volatihty and useful in resin-impregnated air filters, in flexible urethane foam, rebonded foam, and stmctural foam. 

The product is a hquid recommended for flame retarding flexible urethane foams in furniture or automotive seating. It also appears to be useful in polystyrene foam, textile backcoating, and polyester resins. 

Blends of triaryl phosphates and pentabromodiphenyl oxide are leading flame-retardant additives for flexible urethane foams. A principal advantage is their freedom from scorch. 

Nonreactive additive flame retardants dominate the flexible urethane foam field. However, auto seating appHcations exist, particularly in Europe, for a reactive polyol for flexible foams, Hoechst-Celanese ExoHt 413, a polyol mixture containing 13% P and 19.5% Cl. The patent beHeved to describe it (114) shows a reaction of ethylene oxide and a prereacted product of tris(2-chloroethyl) phosphate and polyphosphoric acid. An advantage of the reactive flame retardant is avoidance of windshield fogging, which can be caused by vapors from the more volatile additive flame retardants. 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

Urethane Polymers. An important use for glycerol is as the fundamental building block ia polyethers for urethane polymers (qv). In this use it is the initiator to which propylene oxide, alone or with ethylene oxide, is added to produce ttifunctional polymers which, on reaction with diisocyanates, produce flexible urethane foams. Glycerol-based polyethers (qv) have found some use, too, ia rigid urethane foams. 

In more recent years, molded flexible foam products are becoming more popular. The bulk of the molded flexible urethane foam is employed in the transportation industry, where it is highly suitable for the manufacture of seat cushions, back cushions, and bucket-seat padding. TDI prepolymers were used in flexible foam mol ding ia conjunction with polyether polyols. The introduction of organotin catalysts and efficient siHcone surfactants faciHtates one-shot foam mol ding, which is the most economical production method. 

Aryl phosphates were introduced into commercial use early in the twentieth century for flammable plastics such as cellulose nitrate and later for cellulose acetate.26 In vinyls (plasticized), arylphos-phates are frequently used with phthalate plasticizers. Their principal applications are in wire and cable insulation, connectors, automotive interiors, vinyl moisture barriers, plastic greenhouses, furniture upholstery, and vinyl forms. Triarylphosphates are also used, on a large scale, as flame-retardant hydraulic fluids, lubricants, and lubricant additives. Smaller amounts are used as nonflammable dispersing media for peroxide catalysts. Blends of triarylphosphates and pentabromodiphenyl oxide are extensively used as flame-retardant additives for flexible urethane foams. It has been also... 

Pentaerythritol phosphate has an excellent char-forming ability owing to the presence of the pentaerythritol structure. The bis-melamine salt of the bis acid phosphate of pentaerythritol is also available commercially. This is a high melting solid that acts as an intumescent flame-retardant additive for polyolefins. Synergistic combinations with ammonium polyphosphates have also been developed primarily for urethane elastomers. Self-condensation of tris(2-chloroethyl) phosphate produces oligomeric 2-chloroethylphosphate. It has a low volatility, and is useful in resin-impregnated air filters, in flexible urethane foams and in other structural foams.11... 

Use is made of integral skin foams. They are flexible urethane foams with a high density skin. They are used in applications such as steering wheels, arm rests, and protective covers that must combine a tough surface and a soft feel. 

Uses ANTIBLAZE 100 is used in both virgin and bonded flexible urethane foam. It provides a cost-effective means to pass Cal. 

This reaction is often employed in the production of flexible urethane foams, which are frequently block copolymers of polyether or polyester segments joined to polyurea segments. (The polyester or polyether segments terminate in urethane segments resulting from reaction of polyether or polyester hydroxyl end groups with the isocyanate.)... 

Chemical Blowing Agents. The conventional gas-generation reaction for flexible urethane foams is the water-isocyanate reaction which was first described in a German patent (122). Its chemical reaction is shown as follows ... 

One of the most important properties of flexible urethane foams is cushioning. Figure 6 shows a comparison of hysteresis curves among polyester-, polyether- and HR-foams, respectively. 

Other important properties of flexible urethane foams include indentation force deflection (IFD) or compression force deflection (CFD), compression set, and humid agiiig. 

Applications of Fiexible Urethane Foams. Cushioning materials are the major applicatioii of flexible urethane foams. In 1980, the worldwide consumption of urethane foams was as follows (48) furniture and mattress applications, 37% and automotive applications, 18%. In addition to these applications, a wide variety of additional applications have been reported, including transportation, textiles, packaging, appliances, household materials, medical supplies, sound absorbents, sporting goods, cosmetics, agricultural applications such as artificial soil, and toys. 

Handbook of Plastic Foams Molded Flexible Urethane Foams... 

Molded flexible urethane foams have been used for producing intricate foam products, such as automotive seats and furniture cushions. Molded foams are composed of high-density foam skin and low-density foam core. An example of density distribution of a 10-cm thick molded mattress foam is shown in Figure 9. 

LOAD, kg. FOAMED RUBBER FLEXIBLE URETHANE FOAMS ... 

The effect of the balance between gas generation and polymer formation on foam-cell structure is shown in Figure 12. A formulation for high-resilience, flexible urethane foams is shown in Table 20. 

Preparation of Integral-Skin Flexible Foams. The major polyisocyanates for use in making integral-skin flexible urethane foams are liquid MDl and TDl prepolymers. In order to make light-stable integral-skin foams, aliphatic diisocyanates, e.g., HDl (hexamethylene diisocyanate) and IPDl (isophorone diisocyanate) in modified forms are used. 

Properties of Integral-Skin Flexible Urethane Foams. The foam densities of integral-skin foams of commercial products are in the range of about 300 to 950 kg/m and their Shore A hardnesses are in the range of about 90. Shore D hardnesses are about 40 to 90. Figure 13 shows an example of density distribution of integral-skin foams. 

Due to serious fire hazards caused by flexible urethane foam furniture, very strict regulations have been issued in the State of California (California Technical Bulletin 133), and in the U.K. (British Standard 5852, Part 2, Source 5), as well as in Italy. Because of this... 

As opposed to flexible urethane foams, rigid urethane foams have a highly cross-linked chemical structure and a high percent of closed cells, e.g., over 90%. Rigid urethane foams can be classified as follows unmodified (or pure) rigid urethane foams and modified rigid urethane foams, which include isocyanurate-modified, epoxy-modified, amide-modified and oxazolidone-modified rigid urethane foams. 

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