Synthetic foams

A 2.54-cm Styrofoam plastic foam with thermal conductivity of ca 0.03 W/ (m-K) (0.21 (Btu-in.)/(ft-b°F)) is equivalent to 61 cm of gravel. Any synthetic foam having compressive strength sufficiently high and thermal conductivity sufficiently low is effective. However, the resistance of PS-type foams to water, frost damage, and microorganisms in the sod makes them especially desirable. An interesting and important appHcation of this concept was the use of Styrofoam in the constmction of the Alaska pipeline. In this case, the foam was used to protect the permafrost. 

Honeycomb remove damage, replace with synthetic foam Restores aerodynamic shape and full compressive shape Some loss of impact strength, gain in weight Relatively quick High... 

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. 

A gas suspended in a solid is also called a foam. This form of colloid is relatively rare in nature, unless we stretch our definition of solid to include rock, in which case pumice stone is a colloidal foam. Synthetic foams are essential for making cushions and pillows. There is also presently much research into forming metal foams, which have an amazingly low density. 

Included in manufactured plastics and synthetic foams as flame retardants, especially in electronics, carpets, and furniture... 

A number of factors contribute to the effectiveness of foam as a vapor-suppressant. These include the type of foam, its expansion ratio, its drainage time, the rate of application of the foam (gal per min/ft2), and its application density (gal/ft2). Chemical foams have become obsolete, with mechanical foams now being used worldwide. A mechanical foam that has recognized attributes for vapor suppression is aqueous film-forming foam (AFFF). It is a synthetic foam (as compared to protein foams) with a surfactant that is part fluorochemical and part hydrocarbon. It suppresses vapors by forming an aqueous film produced by draining its foam bubbles. 

The superheated water melts the sulfur in the vicinity of the well, forming a molten sulfur pool at the bottom of the well. As production continues, the formation fills with water. To continue production, bleed wells are drilled at the periphery of the formation to allow for discharge of the cooled mine water. In some mine fields, sufficient mine water is lost to the geological formation to provide for continued production. To limit mine water loss, mud or synthetic foam sometimes is pumped into the formation to seal major crevices. 

Typical sigmoid compressive stress-strain relationships of both synthetic foams and bakery products can be expressed mathematically by a variety of empirical models among them (Swyngedau et al. 1991) ... 

Toxicity. Formaldehyde is very irritant to mucous membranes and inhalation of the vapour causes intense irritation of the respiratory tract which may lead to bronchitis and pneumonia. Atmospheric concentrations of 2 to 3 ppm may cause mild irritation of the mucous membranes and exposure to concentrations of 10 to 20 ppm for only a few minutes may cause moderate to severe irritation. Adverse effects have been reported as a result of release of formaldehyde fumes from synthetic foam insulation. Few fatalities have been recorded but 30 ml of Formaldehyde Solution may be fatal in an adult. The maximum permissible atmospheric concentration is 2 ppm or 3 mg/m. ... 

MIL-R-20092L(1) Rubber or Plastic Sheets and Assembled and Molded Shapes, Synthetic, Foam or Sponge, Open Cell, 25 February 1988, 1 p amend + 17 pp base spec (FSC 9320) (SH)... 

Foams (cellular structures) made by expanding a material by growing bubbles in it [11]. A foam has at least two components. At a macroscopic scale, there are the solid and liquid phases. The solid phase can be a polymer, ceramic or metal. The fluid phase is a gas in most synthetic foams, and a liquid in most natural foams. At a microscopic scale, the solid phase may itself consist of several components. For example, the solid phase of an amorphous polystyrene foam has only one component. On the other hand, the solid phase of a polyethylene foam or a flexible polyurethane foam typically has two components. These components are the crystalline and amorphous phases in polyethylene foams, and the hard and soft phases formed by the phase separation of the hard and soft segment blocks in flexible polyurethane foams. The solid phase of a polyurethane foam may, in fact, have even more than two components, since additional reinforcing components such as styrene-acrylonitrile copolymer or polyurea particles are often incorporated [12,13]. The solid is always a continuous phase in a foam. Foams can generally be classified as follows, based on whether the fluid phase is co-continuous with the solid phase ... 

The history of the science and technology of synthetic foams can be traced from the late 1920s with latex foam. The technologies evolved at that time reached the trial stage in the 1930s. Among rigid foams, low density products were first obtained from special phenolic resins. Before 1942 PE foams had little commercial value. In the USA, the Union Carbide Company initiated development work on low density PE foam as early as 1945. 

Low Density Plastics (Synthetic Foams, Cellular Plastics)... 

The cellular structure of synthetic foams is created by so-called blowing agents. Additives are also often required, particularly nucleation agents and stabilisers. Depending on the process and desired foam density, either chemical or physical blowing agents are applied. 

Synthetic foam is an almost universally used assisting plug material and is mostly used in roller machines. 

The broad applicability of polyurethanes in, for example, synthetic foams paints and adhesives is a driving force to explore these new routes of which the ROP of cychc carbamates or the reaction of cycdic carbonates and amines are major strategies. This section has been purposely restricted to the ROP of cychc carbamates the polycondensation of diamines and cychc carbonates is not included, but has been recently summarized elsewhere [66]. 

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