Polyurethane foam commonly used

As indicated by their name, polyurethanes (PUs), also referred to as urethanes, are a polymer family characterized by the presence of the urethane group (-NH-C0-0-), which is formed by the addition reaction between isocyanate (-N=C=0) and hydroxyl groups (-OH). Polyurethane foams, commonly known as PU foams, PUR foams, or simply PUF, occupy the largest polymer foam market share in terms of consumption, their use being vastly extended to a great variety of applications. Depending on its particular formulation and processing, a vast array of PU foams... 

Polyurethane. SmaU quantities of polyurethane film are produced as a tough mbber-like film. Polyurethane is more commonly used to produce foamed sheet, both flexible and rigid. The flexible foam is used as cushioning in furniture and bedding the rigid foam is widely used for architectural insulation because of its outstanding thermal insulation efficiency (see Urethane POLYMERS). 

Homogeneous catalysis by lin compounds is also of great indusirial importance. The use of SnCU as a Friedel-Crafts catalyst for homogeneous acylation, alkylation and cyclizaiion reactions has been known for many decades. The most commonly used industrial homogeneous tin catalysis, however, are the Sn(ll) salts of organic acids (e.g. acetate, oxalate, oleale, stearate and ocToate) for the curing of silicone elasloniers and, more importantly, for the production of polyurethane foams. World consumption of tin catalysts for the.se Iasi applications alone is over 1000 tonnes pa. 

Polyurethane foams are widely used. Rigid foams, for example, are used in cavity wall insulation in buildings, while flexible foams have, until recently, been used in soft furnishing for domestic use. They continue to be used in car seating. In addition to foams another major use of polyurethanes is in surface coatings. A variety of polyurethane-based polymers, some of considerable complexity, are used for this purpose, but all share the common desirable features of toughness, flexibility, and abrasion resistance. 

Virtually all of the nitrobenzene made is converted to aniline. The most important use of aniline is for the preparation of 4,4 -diaminodiphenyl methane (commonly called methylenedianiline or MDA), an intermediate to one of the main ingredients used to make polyurethane foams and rubber. Aniline is also used to make other rubber chemicals, textile fiber intermediates, dyes, and pharmaceuticals. 

The most common methods for trapping pesticide vapors from air use adsorbents. Common air sampling adsorbents include charcoal (derived from petroleum or coconut) and synthetic polymeric materials, such as cross-linked polystyrene and open-cell polyurethane foam. Charcoal has been used for the cumulative sampling of volatile... 

Another major use for semi-rigid polyurethane foams is as shoe soles. In this application, their light weight, abrasion resistance, and shock absorbing properties are important. In safety shoes, chemical and oil resistance are important. Polyether-based foams are used in applications where microbial attack is common, such as shoes intended primarily for use on soil or grass. 

Polyurethane foam pipeline pigs, which were used at the ordnance plant, can be obtained in diameters from 1/2 to 108 inches in increments of 1/8 inch. The most common sizes used at this plant were 8", 10 , 12" and 16". 

Since the stiffness of a laminate varies as a cubic relationship with the thickness, there are alternate methods employed to achieve thickness - and hence stiffness - than by using multiple layers of fiberglass and resin. Lightweight core materials, such as end-grained balsa wood, high-density polyurethane foam, PVC foam, and honeycombed materials, are available. These materials are sandwiched in between layers of unsaturated polyester resin to achieve increased laminate stiffness. The common terminology used for this technique is sandwich construction . 

Toluene is used more commonly than the other BTXs as a commercial solvent. There are scores of solvent applications, though environmental constraints and health concerns diminish the enthusiasm for these uses. Toluene also is used to make toluene diisocyanate, the precursor to polyurethane foams. Other derivatives include phenol, benzyl alcohol, and benzoic acid. Research continues on ways to use toluene in applications that now require benzene. The hope is that the dealkylation-to-benzene or disproportionation steps can be eliminated. Processes for manufacturing styrene and terephthalic acid—the precursor to polyester fiber—are good, commercial prospects. 

To illustrate some commonly encountered classification methods, a data set obtained from a series of polyurethane rigid foams will be used [76]. In this example, a series of 26 polyurethane foam samples were analyzed by NIR diffuse reflectance spectroscopy. The spectra of these foams are shown in Figure 12.16. Each of these foam samples belongs to one of four known classes, where each class is distinguished by... 

Uses. Production of polyurethane foams and plastics used in polyurethane paints and wire coatings the most commonly used material is a mixture of 80% 2,4 isomer and 20% 2,6 isomers... 

Most useful polyurethanes are cross-linked. Those commonly used in foams start with a diisocyanate like toluene diisocyanate (TDI) and a low molecular weight polyether such as poly(propylene glycol). Recall that the basic reaction of an isocyanate plus an alcohol gives the urethane functionality. 

Toluene diisocyanate is commonly produced as a mixture of the 2,4- and 2,6-iso-niers, that is used as a monomer in the preparation of polyurethane foams, elastomers and coatings, as a cross-linking agent for nylon-6, and as a hardener in polyurethane adhesives and finishes. Polyurethane elastomers made from toluene diisocyanates are used in coated fabrics and clay-pipe seals. Polyurethane coatings made from toluene diisocyanates are used in floor finishes, wood finishes and sealers, and in coatings for aircraft, tank trucks, truck trailers and truck fleets (United States National Library of Medicine, 1997). 

Foams. Polyurethane foams are prepared by the polymerization of polyols with isocyanates. One of the most commonly used reactive isocyanates toluenediisocyanate, TDI. It is made from toluene by nitration and then reduction followed by treatment with phosgene. The isocyanate residue reacts readily with alcohols to give carbamates (urethanes) or amines to give ureas. 

---