Foaming, use

A number of commercial phosphoms-containing polyols have been made by the reaction of propylene oxide and phosphoric or polyphosphoric acid. Some have seen commercial use but tend to have hydrolytic stabiHty limitations and are relatively low in phosphoms content. BASF s Pluracol 684 is a high functionahty polyol containing 4.5% P, sold for Class 11 rigid foam use. 

Polyimide and Melamine. These are both low density, essentially open-ceU foams used as pipe insulations, particularly those involved with fluids operating at temperatures up to 530 K. Because these foams operate at higher temperatures and have improved flammabiHty characteristics compared to other foams, they are also used for some aircraft and marine appHcations. 

Nonstabilized foams are referred to as froths froth-bonded fabrics are similar in properties to some saturation-bonded nonwovens. Typical foams used as nonwoven binder solutions have a consistency similar to shaving cream. AppHcation methods include knife-edge layering onto a horizontal web surface followed by vacuum penetration, and saturation and penetration of a vertical web surface using a horizontal-nip pad. Drying and curing is carried out in ovens, dmm dryers, or steam cans. 

Data on the thermal conductivity for a variety of foams used at cryogenic temperatures have been presented by Kropschot Cryogenic Technology, R. W. Vance, ed., Wiloy, New York, 1963, p. 239). Of aJl the foams, polyurethane and polystiyene have received the widest use at low temperatures. The major disadvantage of foams is that they tend to crack upon repeated thermal cychng and lose their insulation value. 

The law requires nonessential products releasing Class 1 chemicals to be banned within 2 years of enactment. In 1994 a ban wiU go into effect for aerosols and non-insulating foam using Class II chemicals, with exemptions for flammability and safety. Regulations for this purpose will be required within one year of enactment, to become effective tv o vears afterwards. 

There is an increasing market for higher resilience foams using the so-called polymer polyols. Amongst the earliest to become established were suspensions of styrene-aerylonitrile copolymer in the polyol. A variation involved some grafting of SAN, either instead of or in addition to the use of a suspension. 

Cold-curing foams use polyethers of somewhat higher molecular weight (-4500-6000) and which have a higher proportion of primary hydroxyls than are used for hot moulding. In addition the isocyanates used have a functionality greater than 2, this being achieved by the use of modified isocyanates. 

Rigid polyurethane foams used in refrigerators and freezers - Alternatives include hydrocarbons (pentane) and HCFC-141b long-term alternatives include HFCs (134a, -245, -356, -365). Vacuum panels may be used in the future. 

The polyurethane foam used for home insulation uses methanediphenyl-diisoevanate (MDI) as monomer. The MD1 is prepared by acid-cataly/ed reaction of aniline with formaldehyde, followed by treatment w ith phosgene COCl2- Propose mechanisms for both steps. 

Figure 16.22 shows SEM micrographs for the porous media of ceramic support at different magnifications. The non-uniformity resulted from the synthetic foam used as a base to absorb the ceramic solution before vaporising any water from the inorganic mixture. Uniform porous media as a solid support for the membrane was obtained. 

Table 8-27 Example of syntatic foams used in deepwater floatation material...

Coiieotion of pesticide onto poiyurethane foam using high voiume sampier extraotion of PUF using 5% ether in hexane extraot voiume reduction ooiumn oiean-up... 

Mathes, H., Plath, P. J., Generation of monodisperse foams using a micro-structured static mixer, in Proceedings of the Tunisian-German Conference of Smart Systems and Devices, submitted for publication (27-30 March 2001), Hammamet, Tunisia. 

Phospholipids are amphiphilic compoimds with high surface activity. They can significantly influence the physical properties of emulsions and foams used in the food industry. Rodriguez Patino et al. (2007) investigated structural, morphological, and surface rheology of dipalmitoylpho-sphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) monolayers at air-water interface. DPPC monolayers showed structural polymorphisms at the air-water interface as a function of surface pressure and the pH of the aqueous phase (Fig. 6.18). DOPC monolayers showed a... 

Foam use in regular fire-fighting, particularly in industrial situations, has been common for a number of years now. However, foam is a relative newcomer as a tool in combating forest and grassland fires. Wetting agents have been a standard in the field, used to "stretch" the available water supplies in situations where water is often at a premium. 

Foam use requires generators and more sophisticated equipment than wetting agents, and thus... 

Foam used was Macrofoam B (Rockwood Systems) 2% premix, on a UL laboratory generator... 

Foam used was Macrofoam (Rockwood) in a 2% premix. Gantrez AN139 (GAF) was used at a 3% concentration. 

Low expansion foams are typically applied to the surface of exposed flammable liquids, especially in outdoor areas. High expansion foams are commonly applied to large enclosed areas where high winds would not affect the foam usefulness and where interior locations are hard to reach. 

Colloidal particles, foams used to collect and separate, 12 22 Colloidal powders, 23 55-56 Colloidal silica, 22 380, 382, 384 applications of, 22 394 modification of, 22 393-394 preparation of, 22 392-393 properties of, 22 391-392 purification of, 22 393 Colloidal silica gels, 23 60 Colloidal solids, 7 293-294 Colloidal stability, 7 286-291 10 116 22 55 Colloidal stabilizers, in polychloroprene latex compounding, 19 857 Colloid mills, 8 702 10 127 Colloids, 7 271-303 23 54. See also Polymer colloids analysis, 7 296 applications, 7 292-296 conducting, 7 524... 

In practical application, it was reported that the platinum particles dispersed in highly porous carbonized polyacrylonitrile (PAN) microcellular foam used as fuel-cell electrocatalyst160 have the partially active property. The fractal dimension of the platinum particles was determined to be smaller than 2.0 by using the potentiostatic current transient technique in oxygen-saturated solutions, and it was considered to be a reaction dimension, indicating that not all of the platinum particle surface sites are accessible to the incoming oxygen molecules. 

Long-lasting foam Use anionic or amphoteric surfactants, or a mixture of the two for high foaming... 

The following information concerns foams for sandwich technology only and not foams used for packaging or insulation. 

PVC foams used as sandwich cores generally have ... 

Generally, the properties of the polystyrene foams used for sandwich technology are ... 

Microscope image of a Ni metal foam used as a DL in direct methanol fuel cells (reference bar indicates 1 mm). (Reprinted from S. Arisetty et al. Journal of Power Sources 165 (2007) 49-57. With permission from Elsevier.)... 

Metal foams have been used in the past in the development of FF plates. However, Gamburzev and Appleby [53] used Ni foams as both a DL and a flow field plate with an MPL layer on one of its surfaces. They observed that such a design had high contact resistance between the nickel foam and the MPL and also increased gas diffusion resistance due to the required MPL thickness. Arisetty, Prasad, and Advani [54] were able to demonstrate that these materials can also be used as potential anode diffusion layers in DMFCs (see Figure 4.10). In fact, the nickel foam used in this study performed better than a carbon cloth (Avcarb 1071HCB) and a stainless steel mesh. However, it was recognized that a major drawback for these foams is their susceptibility to corrosion. 

Neoprene. An elastomer with the repeating structure, -C4H7CI-, that comes in the form of solid, latex, and flexible foam. Used as coatings, sealants, protective garments, adhesive tapes, etc. 

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