Foams high resiliency

Fabric Standard PU Foam High Resilience PU Foam High Resilience PU Foam FR Cotton Barrier Fabrics High Resilience PU Foam PU Barrier Foam ... 

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. 

HR foam (high-resilient foam) is sometimes classified as a cold-molded foam because it can be molded at low temperatures. However, HR foams have slightly different formulations than standard cold-molded foams. There are many kinds of molded-foam formulations in the literature. The following formulations are only a few examples. 

Commonly used isocyanates are toluene dhsocyanate, methylene diphenyl isocyanate, and polymeric isocyanates. Polyols used are macroglycols based on either polyester or polyether. The former [poly(ethylene phthalate) or poly(ethylene 1,6-hexanedioate)] have hydroxyl groups that are free to react with the isocyanate. Most flexible foam is made from 80/20 toluene dhsocyanate (which refers to the ratio of 2,4-toluene dhsocyanate to 2,6-toluene dhsocyanate). High-resilience foam contains about 80% 80/20 toluene dhsocyanate and 20% poly(methylene diphenyl isocyanate), while semi-flexible foam is almost always 100% poly(methylene diphenyl isocyanate). Much of the latter reacts by trimerization to form isocyanurate rings. 

In addition to freedom from bottoming out , most people prefer a seat which effectively provides a soft surface with a firm interior. One measure of the relationship between such surface softness and inner support is the sag factor or support factor. In one commonly used test this is obtained by dividing the force required to compress a foam by 65% of its height by the force needed to obtain 25% sample compression. This generally increases with density but is typically <2.5 for a conventional slabstock foam but >2.5 for a high-resilience foam. 

There is also growing interest in multi-phase systems in which hard phase materials are dispersed in softer polyether diols. Such hard phase materials include polyureas, rigid polyurethanes and urea melamine formaldehyde condensates. Some of these materials yield high-resilience foams with load deflection characteristics claimed to be more satisfactory for cushioning as well as in some cases improving heat resistance and flame retardancy. 

The work (3) confirmed the correctness of the decision not to enforce the use of flame retarded PU foam and showed that although high resilience PU foams and flame retarded PU foams themselves were more difficult to ignite, this advantage was often lost when they were used in furniture as fabric covered composites. Early flame retarded PU foams were more likely to produce greater smoke and in some circumstances could burn more rapidly than composites containing standard PU foam. 

Various UK government authorities and especially The Crown Suppliers were already "fire conscious" and further extended the use of fabrics of reduced flammability, barrier fabrics and barrier foams, with high resilience PU foams in their purchase specifications for upholstered furniture and bed assemblies for use in the Crown Estate, public buildings, hospitals etc. Typically, products were required to meet cigarette and No. 5 wooden crib sources see Table I when tested to Crown Suppliers Tests (5), (6). ... 

Cold cure" or high resilience PU foams tended to liquify before igniting were developed and gave good results in standard tests such as BS 4735(25) (similar to the discontinued ASTM D1692) but could still burn when used with flammable fabrics in furniture (Table IV). However they have been used most successfully in the UK in combination with flame retarded cotton interliners and fabrics of low flammability e.g. wool, nylon, FR cotton etc. and formed the basis of public area furniture used in the UK since the early 1970 s (Table V). 

These criteria were developed by the UK PU foam industry and were intended to differentiate the melamine or exfoliated graphite containing combustion modified PU foams from the standard, high resilience and flame retarded (chloro and bromo phosphate) containing PU foams (Table IV). This distinction was required because large scale burning tests of real arm chairs and furnished rooms had demonstrated the superiority of the combustion modified polyurethane foams. 

The resulting slate of polyols has been demonstrated in conventional flexible slabstock foam [143], viscoelastic foam [144], and high resiliency slabstock and molded foams [145],... 

By crosslinking, the viscosity of EVA at high temperatures is increased and the individual cells are kept in a stable condition without rupture or agglomeration. A low density microcellular foam can be thus obtained. By selecting the vinyl acetate content, the EVA foam is flexible and highly resilient with easy coloring and adherent to other materials. The application is used widely in shoe soles, sandals and cushion materials. 

The two primary hydroxyl groups provide fast reaction rates with diisocyanates, which makes this diol attractive for use as a curative in foams. It provides latitude in improving physical properties of the foam, in particular the load-bearing properties. Generally, the ability to carry a load increases with the amount of 1,4-cydohexanedimethanol used in producing the high resilience foam (95). Other polyurethane derivatives of 1,4-cyclohexanedimethanol indude elastomers useful for synthetic rubber products with a wide range of hardness and elasticity (96). 

The steric effects in isocyanates are best demonstrated by the formation of flexible foams from TD1. In the 2.4-isomer (4), the initial reaction occurs at the nonhindered isocyanate group in the 4-position. The unsyinmeli ically substituted ureas formed in the subsequent reaction with water are more soluble in the developing polymer matrix. Low density flexible foams are not readily produced from MDi or PMDi enrichment of PMDI with Ihe 2,4 -isomcr of MDi (5) affords a steric environment similar to the one in TDI, which allows the production of low density flexible foams that have good physical properties. The use of high performance polyols based on a copolymer polyol allows production of high resiliency (HR) slabstock foam from either TDI or MDI. 

With amine initiators the so-called self-catalyzed polyols are obtained, which are used in the formulation of rigid spray foam systems. The rigidity or stiffness of a foam is increased by aromatic initiators, such as Mannich bases derived from phenol, phenolic resins, toluenediamine, or methylenedianiline (MDA). In the manufacture of highly resilient flexible foams and thermoset RIM elastomers, graft or polymer polyols are used. 

Flame retardants are incorporated into the formulations in amounts necessary to satisfy existing requirements. There are four main types of flexible slabstock foam conventional, high resiliency, filled, and high load-bearing foam. 

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 die manufacture of seat cushions, back cushions, and bucket-seat padding. TDl prepolymers were used in flexible foam molding in conjunction with polyether polyols. The need for heat curing has been eliminated by the development of cold-molded or high resiliency foams. 

McGovern, M. High resiliency polymethane foams with improved static fatigue properties, PCT US Patent 5157056, assigned to ARCO Chemical Technology, 1992. 

The polyisocyanates which can be used for preparing isocyanate-based foams are mainly aromatic compounds and some aliphatic or aralkyl polyisocyanates. TDI (toluene diisocyanate) is widely used for flexible foams. Pure MDI (diphenylmethane diisocyanate) is used for elastomers and coatings. Modified TDI and modified MDI are used for high-resilience flexible foams. Polymeric isocyanates (polymeric MDI or oligomeric MDI) are mostly used for preparing rigid urethane and isocyanurate foams, and in part, for preparing flexible and semi-flexible foams. 

The influence of DBU mono(2-ethylhexanoate) catalysis on the process-ability and physical properties of high-resiliency polyurethane foams has been reported (81MI2),... 

---