Foamed-in-place materials

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 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... 

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. 

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 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]. 

Polyether Cushioning Material, Foam-in-Place, Flexible(1991)... 

Plastic Material, Cellular Polyurethane, Foam-in-Place, Rigid (3 pounds per cubic foot density) (1980)... 

Foam-in-Place Packaging Materials, General Specification for (1990)... 

ASTM D 4168-88 Standard Test Methods for Transmitted Shock Characteristics of Foam-in-Place Cushioning Materials, 5 pp (Comm D-10)... 

MIL-C-8087C (ASG) Core Material, Foamed-in-Place, Urethane Type, 24 April 1968, 15 pp (FSC 9320) (AS)... 

This Navy specification covers a single class of foam, nominal density 2.0 Ib/ft rigid unicellular polyurethane foam, and the materials required for preparation by the foam-in-place technique. Requirements cover density, compressive strength, volume change after heat aging, humidity aging, compressive set, unicellularity (% open cells, max.), oil resistance, and fire resistance. 

MIL-P-24249(1)(SHIPS) Plastic Material, Cellular Polyurethane, Rigid, Void Filler, Foam-in-Place, Large Scale and Installation of, 6 November 1967, 3 pp amend + 13 pp base spec (FSC 9330) (SH) (QPL)... 

Covers a rigid polyurethane foam kit for use in certain nuclear ordnance, explosive ordnance disposal operations. The system is a three-component liquid foam-in-place type for use in immobilizing materials and objects. 

MII P-43226A(MI) Polyether Cushioning Material, Foam-in-Place, Flexible, 28 June 1991, 10 pp (FSC 8135) (MI)... 

Notice 1 (30 July 1987) validated the specification. This is the Air Force foam-in-place specification. It covers the materials required and the preparation of the formulation used in the process. 

The principal end use of urea is to provide combined nitrogen for solid fertilizer formulations. Some urea is also converted to biuret (H2NCONHCONH2, also called carbamoyl urea) and to a sulfur derivative, which are sold as Kedlor [65] and Urasil [66] cattle feed supplements, respectively. Urea is also used to a lesser extent in the manufacture of plastics components, such as melamine, and as a component of urea-formaldehyde resins used as adhesives. It is also used as a component of foam-in-place formulations as a rigid insulating material [67], and as an ingredient in noncorrosive aircraft deicing solutions [67a]. 

Cushioning materials in widespread use include air bubble sheet, cellulose padding, cork-based granules/sheet, corrugated plastic comers, corrugated sleeves, embossed paper, expanded polystyrene, other expanded plastics, foam in place, free flow polystyrene, sawdust and shavings, straw, wood wool. 

Potential applications include use as an insulative base for foundations and highways, in the manufacture of foam core panels, and as a general filler or insulation material. Sulfur foams can be foamed in place, and this property enhances their value in many applications. 

Figure 1-10. A typical use of polyurethane foam-in-place insulation material in wall construction. 

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