Foamed-in-place

Foaming extrusion Foaming-in-place beads Foaming power Foam inhibitors... 

The combination of stmctural strength and flotation has stimulated the design of pleasure boats using a foamed-in-place polyurethane between thin skins of high tensUe strength (231). Other ceUular polymers that have been used in considerable quantities for buoyancy appHcations are those produced from polyethylene, poly(vinyl chloride), and certain types of mbber. The susceptibUity of polystyrene foams to attack by certain petroleum products that are likely to come in contact with boats led to the development of foams from copolymers of styrene and acrylonitrUe which are resistant to these materials... 

Table 11. Loss of Isopentane from Foaming-in-Place Chlorostyrene Beads in Open Storage, wt %...

Available forms. Blanket (felt and batt), block, cements, loose fiU, foil and sheet, formed or foamed in place, flexible, rigid, and semirigid. 

There are many ways in which foams can be processed and used as slabs, blocks, boards, sheets, molded shapes, sprayed coatings, extruded profiles, foamed in place in existing cavities, in which the liquid material is poured and allowed to foam, and as structural foams (Chapter 6, STRUCTURAL FOAM). Conventional equipment such as extruders, injection, or compression machines is used. However specially designed machines are available to just produce foamed products. 

Disposal of Plastics with Emphasis on Foam-in-Place Polyurethane Foam , PLASTEC Rept R37A (1973) 39) J.B. Titus, Environmental-... 

Chlorostyrene, monomeric, 23 368 Chlorostyrene beads, foaming-in-place, 23 406t... 

Applications. The principal use for rigid polyurethane foams is lor insulation in various forms utilized by a variety of industries. Packaging constitutes another significant use and is often a foam-in-place opcralion lo protect industrial equipment such as pumps or motors. 

While unaffected by water, styrofoam is dissolved by many organic solvents and is unsuitable for high-temperature applications because its heat-distortion temperature is around 77°C. Molded styrofoam objects are produced commercially from expandable polystyrene beads, but this process does not appear attractive for laboratory applications because polyurethane foams are much easier to foam in place. However, extruded polystyrene foam is available in slabs and boards which may be sawed, carved, or sanded into desired shapes and may be cemented. It is generally undesirable to join expanded polystyrene parts with cements that contain solvents which will dissolve the plastic and thus cause collapse of the cellular structure. This excludes from use a large number of cements which contain volatile aromatic hydrocarbons, ketones, or esters. Some suitable cements are room-temperature-vulcanizing silicone rubber (see below) and solvent-free epoxy cements. When a strong bond is not necessary, polyvinyl-acetate emulsion (Elmer s Glue-All) will work. 

Foamed-in-place polyurethane is prepared by allowing a polyol [po y(ethy ene glycol), polyester alcohols, etc.] to react with a diisocyanate in the presence of an amine catalyst. The gas which creates the foam may be a dissolved material, such as a Freon, which volatilizes during the exothermic polymerization reaction.7 A second method involves the use of water in the reaction mixture this hydrolyzes part of the isocyanate to produce an amine and C02 gas. The Freon-formed material is preferred for the insulation of low-temperature apparatus because the thermal conductivity of the foam is greatly reduced at low temperatures by the condensation of the Freon in the cells. It is probable that the longterm effectiveness of this phenomenon must be maintained by surrounding the foamed plastic with an airtight enclosure which will prevent diffusion of air into and Freon out of the cells. 

Flexible PUR foam, such as that used in upholstery, is made by continuous deposition on a belt before being cut into blocks or sheets of desired shape and size. Other foam materials may be handled in somewhat similar ways, and may be pre-foamed or foamed-in-place. 

The sulfur foams for these tests were foamed-in-place with pilot field equipment at a foaming rate of 100 lb/min. Installation, instrumentation, and performance of these tests have been reported in detail (1,2). Field surveillance data and sample analysis over two years so far indicate design insulation effectiveness and property integrity (Figures 1 and 2, Table I). 

Large-scale uses for this type of foamed-in-place insulation and application equipment are anticipated as the Canadian Arctic is developed. Successful results from these field tests and the prospects of commercial uses of the sulfur foam prompted Chevron Chemical Co. to proceed with the design, engineering, construction, and demonstration of a commercial-scale sulfur foam field application unit. 

Figure 9. Two 10-ft wide and 150-ft long strips of 74b/ft3 sulfur foam foamed in place side-by-side...

The low thermal conductivity of polyurethanes, plus the ease of application and structural properties of foamed-in-place materials, affords great freedom of design. As a result, rigid polyurethane foams have displaced rock wool and glass wool in freezers and refrigerators. 

The moisture resistance, low cost, and low-density closed-cell structure of many cellular polymers resulted in their acceptance for buoyancy in boats, floating docks, and buoys. Because each cell is a separate flotation unit, these materials cannot be destroyed by a single puncture. Foamed-in-place polyurethane between thin skins of high tensile strength is used in pleasure craft [98]. Other cellular polymers that have been used where buoyancy is needed are produced from polystyrene, polyethylene, poly(vinyl chloride), and certain types of rubber. Foams made from styrene-acrylonitrile copolymers are resistant to petroleum products [99,100]. 

Foaming-in-place by pouring ftom a dual- or multi-component head. 

Foam-In-PIace. The foam-in-place (or pour-in-place) method is used for the production of refrigerators, deep freezers, sandwich panels, and similar applications. This process is also used for field applications, such as indoor- and outdoor-tank insulation (79), LPG (liquefied petroleum gas) tank insulation, heavy oil-tank insulation, chemical-tank-car insulation, and pipe-covering insulation, among others (79). 

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