Special foams

These foams can be defined as composites consisting of hollow microspheres and a polymeric matrix. This one is made of a thermosetting (PU, PIR, PF, EP, silicone or unsaturated polyester) or of a thermoplastic (PE, PP, PVC, PS, polyimide) [56]. The microspheres can be made of silica, glass, carbon, ceramics or polymers such as PS, PE, PP, polyamide (PA), polymethyl methacrylate (PMMA), divinyl benzene (DVB)-maleic anhydride, and so on [56-58]. The diameter of the tiny hollow spheres is 300 mm or less [35]. They contain an inert gas such as nitrogen or a CFC. The properties of these syntactic foams depend on matrix type, microsphere type (and the contained gas), ratio matrix to microspheres, curing process, production technology. Syntactic foams can be made in combination with the conventional ones. Such a complex composite can be formnlated into a mouldable mass then shaped or pressed into cavities. 

Epoxy syntactic foams are the best-known representatives of this type of special foam. The main disadvantage of snch a matrix is its high viscosity at ambient temperature, but the adding of dilnents can circumvent this [20]. 

Microcellular polymers are closed cell thermoplastics produced by gas nucleation. They have a high number of very small cells with a diameter of 10 pm, and bubble densities in excess of 100 million per cm. First produced in the early 1980s with the objective of reducing the amount of polymer used in mass produced items, these novel materials have the potential to revolutionise the way thermoplastic polymers are used today. PVC, PS, polycarbonate (PC), polyethylene terephthalate (PET) and not only these polymers can be applied for such kinds of products. As no harmful chemicals are used in the microcellular technology, it is likely that these new products will replace many types of foam now produced by processes that damage the environment [59]. 

The acoustic characteristics of polymers are altered in a cellular structure. Sound transmission changes only slightly, because it depends mainly upon the barrier density, in this case the polymer phase. Therefore polymeric foams are poor materials for reducing the transmission of the sounds. They are however, effective in absorbing sound waves of certain frequencies. 

In open cell structures the gas is air and for this reason they have a higher absorptive capacity of moisture, a higher gas and vapour permeability, less effective insulation capabilities for either heat or electricity, and a better ability to absorb and dampen sound. Eor any polymer composite, the proportion of open gas structural elements increases as the density of the foamed plastic decreases, because an increase in cell size means a decrease in the thickness of cell walls and ribs [60]. The combination of other advantageous physical properties with fair acoustic characteristics has led to the use of plastic foams in sound proofing [31]. 

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Toxic products may be produced care must be exercised after use in confined spaces. Special foam required for water-miscible liquids. 

Lithium alcohol sulfates are used in carpet-cleaning formulations due to their special foaming characteristics. 

When a-sulfo fatty acid esters are used as the major active component in detergents they can cause problems because of their foaming properties. In European horizontal drum-type automatic washers they produce too much foam, and in the rinse cycle of the American and Japanese pulsator-type washers the foam cannot be completely rinsed out [38]. The problem of inefficient rinsing can be solved by the addition of soap [63] or sulfonated unsaturated fatty acid esters [64]. For European applications special foam inhibitors are needed. 

Special alcohol resistant (or compatible) type foam is needed for application to alcohols, esters or ketones type liquids and organic solvents, all of which seriously break down the commonly used foams. Commercially available foam products are now available that can be used on both alcohols and hydrocarbons, only alcohols or only hydrocarbons. It is therefore imperative to design foam systems in a cost effective fashion if several products are in use that may require special foam application requirements. 

Almost all of titanium s compounds, as weU as the pure metal when in powder form, are extremely flammable and explosive. Titanium metal wiU ignite in air at 1200°C and wiU burn in an atmosphere of nitrogen. Titanium fires cannot be extinguished by using water or carbon dioxide extinguishers. Sand, dirt, or special foams must be used to extinguish burning titanium. 

Some types of foam are not suitable for water miscible or polar solvent liquids. Special foams designed for fighting fires involving these materials are available. For more information on low-expansion foam systems refer to NFPA 11, Low-Expansion Foam Systems. For additional information on medium- and high-expansion foam systems, refer to NFPA 11 A, Medium- and High-Expan-sion Foam Systems. 

A Firemen race against time to put out the fire before it reaches the aircraft s fuel tanks. The first priority is to keep the air away from the flames. This is done by smothering the flames with a special foam made up of bubbles containing carbon dioxide, in which things cannot burn. Foam has two advantages over water. It can be concentrated on its target more easily, and is easier to transport. 

Fires involving combustible metals such as magnesium are Class D fires. Special foam compounds are needed to extinguish these fires. 

Barge Loading (Figure A-l). Chevron melter-mixers, special foam truck and trailer, plus all support equipment are loaded on a barge for... 

Loading Precursor into a Nurse Tank (Figure A-4). The hot foam precursor is loaded into a tank truck for delivery to the special foam unit. This step pays off when foaming is required at sites removed from the base of operations. The foamer is then used more efficiently with resulting higher lay-down rates per day. Drums of foaming agent are also delivered to the foam unit at the same time. 

The low molecular protein, the antibiotic nisin, was successfully concentrated in industrial scale from a culture liquid in a high expansion ratio foam, stabilised with the foaming agent Tween-80. In the absence of a special foaming agent no stable foam was produced from the culture liquid. Nisin could be extracted by adding Tween-80, though the... 

In addition to water, auxiliary blowing agents may be included in the foam formulation to further reduce the foam density (16) (17). These agents can be used in addition to, or as part replacement for the water in developing special foam properties. An example is the use of methylene chloride or CFC-11 in either polyether- or polyester-based systems for softening the resulting foam. A number of other volatile solvents are known to have been used also. 

Saponins are natural extracts known as glycosides that have special foaming and soapy properties. As a glycoside, a saponin may have binding properties for water in the skin. Some studies show that saponins have an antimicrobial effect. They are also used to even out penetration of the acids through the skin and enhance skin healing. 

Polymeric substrate materials in use include highly filled phenolic and epoxy resins for rigid printed circuit boards, polyimides and polyesters for circuit substrates as well as for more general applications, special foamed poly(tetrafluoroethylene) polymers and copolymers, foamed composite materials of the latter, special epoxy fiberglass composites, and polyimide support layers for TAB. In addition, epoxies and silicone polymers are used increasingly in applications as encapsulants, as humidity and environmental barriers within packages, and as packaging materials themselves. 

Special Processes. Several more recent developments have opened the possibility of special foam processes that may grow to tremendous importance and perhaps even change the entire concept of foamed plastics. These are structural foam, reaction injection molding (RIM), and syntactic foam. 

Lather Lube. [Alex C. Fergusson] Special foam detergent lubricants fix conveyors. 

A good deal of flexible urethane foam is now being made by the cold-cure technique. This involves more reactive polyols and isocyanates in special foaming formulations which would cure in a reasonable time to their maximum physical properties without the need for additional heat over and above that supplied by the exothermic reaction of the foaming process. 

In order to produce safely and go over the fire zone successfully, mixed the FR-1 polymer liquid foam inhibitor and water according to the proportion of 1 2 (Xu 2010). Use special foam device to create the inhibitor foam. And then put out fire... 

Alcohol-resistant foam Alcohols, ketones and esters can break down many types of foam, thus cancelling out the extinguishing action fires involving these materials need to be fought with special foams which do not break down as readily. AFFF-ATC also falls under this category. 

Protection against eye splashes and against absorption via cuts and other breaks in the skin is required. Methanol burns with a non-luminous flame and in fire fighting great care must be taken not to be trapped by an uimoticed fire. Normal foam is not effective in fighting methanol fires because it causes the foam to collapse. If methanol is stored on a site, supplies of a special foam are needed. 

The functioning of these sprinklers can be initiated by an electronic detection system, or by heat-sensitive valves at each sprinkler head. When a fire is detected, a spray (or more recently, a mist) of water is emitted. The water absorbs the heat of the fire through a phase change to steam and thus arrests the combustion cycle. In certain appHcations where oil fires are expected, such as in restaurant kitchens, a special foam or gel replaces the water in the system. 

To modify the cocamidopropyl betaine for special foam and viscosity requirements, the fatty acid composition is often adjusted. Examples include betaines based on stripped coconut fatty acid with only a very small... 

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