Foam layer

Fig. 4. Cross-sectional view of vinyl-coated fabric with PVC foam layer.

Goldberg and Rubin [Ind. Eng. Chem. Proce.s.s Des. Dev., 6 195 (1967)] showed in tests with a disk spinning vertically to the foam layer that most mechanical procedures, whether centrifugation, mixing, or blowing through nozzles, consist basically of the application of shear stress. Subjecting foam to an air-jet impact can also provide a source... 

Ferric hydroxide coprecipitation techniques are lengthy, two days being needed for a complete precipitation. To speed up this analysis, Tzeng and Zeitlin [595] studied the applicability of an intrinsically rapid technique, namely adsorption colloid flotation. This separation procedure uses a surfactant-collector-inert gas system, in which a charged surface-inactive species is adsorbed on a hydrophobic colloid collector of opposite charge. The colloid with the adsorbed species is floated to the surface with a suitable surfactant and inert gas, and the foam layer is removed manually for analysis by a methylene blue spectrometric procedure. The advantages of the method include a rapid separation, simple equipment, and excellent recoveries. Tzeng and Zeitlin [595] used the floation unit that was devised by Kim and Zeitlin [517]. 

An alternative way to look at the problem might be to ask the question, What initial fill fraction should be specified in the tank to avoid two-phase flow during a fire exposure incident No tested correlations are presently available to compute the height of a foam layer above the boiling liquid. 

A gas suspended in a liquid is called a foam. Obvious examples include shaving foam (the gas being butane) and the foam layer generated on the surface of a warm bath after adding a surfactant, such as bubble bath . The gas in this last example will be air, i.e. mainly nitrogen and oxygen. 

Foam breaks down and vaporizes its water content when exposed to heat and flame. Therefore, it must be applied to a burning surface at a sufficient rate to compensate for this loss and to ensure a residual foam layer over the liquid. 

Multi-layer sheets for use in the mannfacture of food packaging containers were produced by the coextrusion of PP foam in combination with PE, an EVOH barrier layer and tie layers. Results are presented of studies of the mechanical and morphological properties, density and cell stmctnre of foam layers based on different types of PP. 8 refs. 

The sheet comprises a foamed layer (a) composed of polypropylene, at least one surface of which is directly adhered to a substantially unfoamed layer (b) comprising an ethylene-based polymer. The resin employed for the foamed layer is a blend of at least about 50% by weight of polypropylene and from about 3 to less than about 50%... 

These compositions may comprise a single ethylene/ alpha-olefin or a blend thereof and, optionally, at least one diluent including waxes, plasticisers, such as oil, polymeric tackifiers or mixtures thereof. They may be used as cabinet sealants and as foam layers in disposable articles, such as nappies, incontinence devices and medical devices, such as bandages and dressings. 

Patent Number EP 916465 A1 19990519 COMPOSITE POLYPROPYLENE MATERIAL HAVING MOULDED AND FOAMED LAYER AND METHOD OF PRODUCING SAME... 

An integrally monlded composite article comprised of (I) a nonfoam layer formed from a thermoplastic elastomer powder composition (A) and (II) a foam layer formed from a foamable composition comprised of (i) (B) a thermoplastic synthetic resin powder, and (C) a heat decomposable foaming agent and (D) a liquid coating agent, wherein the thermoplastic elastomer powder (A) is comprised of a composition of an ethylene-alpha-olefm copolymer mbber and a polyolefin resin or thermoplastic elastomer powder comprised of a partially crosslinked composition of an ethylene-alpha-olefm copolymer mbber and a polyolefin resin, the thermoplastic elastomer powder having a complex dynamic viscosity at 250 deg C and a freqnency of 1 radian/sec of not more than 1.5x1,000,000 poise and having a Newtonian viscosity index n, calculated by a specific formula. 

A formed laminate is made by relative movement of first and second contoured mould surfaces toward each other to compress a flexible sheet and vertically spaced film with a foamable liquid mixture therebetween that has substantially completed expansion but not yet substantially cured so as to form the flexible sheet and provide a collapsed foam layer bonded to the sheet. The flexible sheet is preferably porous cloth, vinyl or leather. A film which is preferably a nonadherent plastic such as PE is preferably positioned in a vertically spaced relationship with the flexible sheet either above or below the sheet with the foamable liquid mixture received therebetween for the expansion prior to the compression that provides the formed laminate. The formed laminate... 

Patent Number US 5281376 A 19940125 METHOD FOR PRODUCING PP RESIN ARTICLE HAVING SKIN MATERIAL LINED WITH FOAMED LAYER... 

As drops of this dispersed phase collect near the separation interface, they will flocculate into a closely packed mass which can best be described by the term liquid-liquid foam. Each drop is surrounded by a thin film of the continuous phase. The film between two adjacent drops can rupture and the two combine by coalescence in the foam layer. Only those drops near the general phase boundary can coalesce into the general drop phase layer. The residence time in the flocculation zone can be many minutes, and considerable mass transfer may occur there. 

In a 4-1. beaker equipped with a stirrer which can be operated above the liquid level to break the foam are placed 250 ml. of 12 N hydrochloric acid and 250 ml. of water. The filtrate obtained above is cooled to about 50° and is added to the hydrochloric acid in small portions and at such a rate that the mixture does not foam over. If efficient stirring is used in the foam layer, this addition can be carried out in 5 minutes. The product is isolated by filtration through a Buchner funnel and is washed on the filter, first with a 250-ml. portion of dilute hydrochloric acid (prepared by diluting 50 ml. of 12 N hydrochloric acid to about 250 ml.) to remove anthranilic acid, and then with 500 ml. of water. The product is sucked as dry as possible and is then spread in a thin layer and allowed to air dry for about 15 hours. When easily pulverizable, the material is transferred to an oven and dried for 3 hours at 100-120°. 

Bavarian F, Fan LS, Chalmers JJ. Microscopic visualization of insect cell-bubble interactions. I rising bubbles, air-medium interface, and the foam layer. Biotechnol Bioeng 1991 7 140-150. 

Profiles of foam density, derived from gamma ray scans of the separators, showed that no discrete foam layer was in the vessels, but a two-phase mixture of gas and liquid occupied a substantial pan of the total height of the vessel. 

In coffee products, such as espresso, a stable foam is an important aspect of overall product quality, in addition to smell, taste, colour, and body [857]. In addition to appearance, a foam layer helps trap coffee aromas, providing a more gradual release. The degree of foaming has been found to increase with the degree of roast and the amount of protein in the coffee, while the stability of the produced foam has been related to the amounts of galactomannan and arabinogalactan [857]. 

A type of foam in which solid particles are also dispersed in the liquid (in addition to the gas bubbles), as in froth flotation. The solid particles can even be the stabilizing agent alternatively, the foam layer produced at the top of a separation vessel or distillation tower. The term sometimes refers simply to a concentrated foam, but this usage is not preferred. 

Retarding oxidative weight loss of the foamed layer at 1000°C or even higher... 

Methods which enploy liquid phase treating liquors (spray, transfer rolls and belts, etc.) share a cannon difficulty stemming from the lew volume of liquor in relation to the large surface area of the fibers conprising the substrate to be treated. This difficulty is acerbated when aqueous liquors are to be applied to hydrophilic fibers. Foam coating methods enploy stable foams which allow the thickness of the liquid-air mixture to be controlled by a doctor blade or roll. Conparatively low add-ons can be achieved by virtue of the low density of the foam layer, but the stable nature of such foam, and its immobile liquid phase, inhibit rapid, uniform distribution through the substrate. 

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