Insulation systems using foams

Two foam insulation systems prepared by the A. D. Little Company of Cambridge, Massachusetts were also tested. These systems had two vapor barriers, one on the outer surface (Z/Z x and one at Z/Zj j x 0.62 (where Z is the distance into the insulation from the outer surface and Z the insulation thickness). Each vapor barrier was a laminate composed of one layer of mylar [0.013 mm (0.0005 in) thick], two layers of aluminum [0.025 mm and 0.013 mm (0.001 in and 0.0005 in) thick], another layer of mylar [0.013 mm (0.0005 in)], and a layer of dacron woven fabric [33.9 g/m (1.0 oz/yd )]. The two layers of mylar offer tensile strength, the two layers of aluminum resist gas diffusion, and the dacron cloth resists tearing. Both systems used foams which had chopped fiberglass added for reinforcement. One system used Sta-foam AA1602 (a toluenedi isocyanate), whereas the other used Upjohn 452 (a pol3nnetric isocyanate). As can be seen from Fig. 13b, both systems had fair thermal performance Initially, but the performance deteriorated rapidly with thermal cycles. 

A variety of cellular plastics exists for use as thermal insulation as basic materials and products, or as thermal insulation systems in combination with other materials (see Foamed PLASTICS). Polystyrenes, polyisocyanurates (which include polyurethanes), and phenolics are most commonly available for general use, however, there is increasing use of other types including p olye thylene s, polyimides, melamines, and poly (vinyl chlorides) for specific applications. 

The use of this catalytic system permits foam formation to proceed without the need to supply external heat to the reaction mixture after the reactants are brought together. This permits pouring-in-place of the foam-forming system, for example, in the insulation of cavity walls for construction purposes, in trailer walls, and in cold-storage firameworks and the like. 

Uses Binder for emulsion paints, textured finishes, and thermal insulation systems adhesive for flooring, walls, foam, tiles Prr rerries Disp. 0.1 pm particle size vise. 9000 3000 mPa s pH 7 tens. str. 4 N/mm tens, elong. 600% (break) 50 1% solids... 

Aging and conditions of aging are significant factors in the mechanical and thermal performance of PS and PU. It is particularly important for foams in cryogenic service to be shielded from water vapor. If this is not done, moisture will permeate the cells, form ice, and result in damage to the cells in addition to increasing the thermal conductivity. Insulation systems for use on LNG tankers enclose the foam in membranes of plastic or metal. Accelerated tests on these systems indicate a functional lifetime in excess of 20 years. 

Polyurethane, PVC, and extruded polystyrene provide the bulk of the cellular plastics used for low and cryogenic temperature appHcations. In some cases, eg, the insulation of Hquid hydrogen tanks on space systems, foams have been reinforced with continuous glass fibers throughout the matrix. This improves strength without affecting thermal performance significantly. 

Foam. PhenoHc resin foam is a cured system composed of open and closed ceUs with an overall density of 16—800 g/cm. Principal appHcations are in the areas of insulation and sponge-like floral foam. The resins are aqueous resoles cataly2ed by NaOH at a formaldehyde phenol ratio of ca 2 1. Free phenol and formaldehyde content should be low, although urea may be used as a formaldehyde scavenger. 

Silicone foam thus formed has an open ceU stmcture and is a relatively poor insulating material. Cell size can be controlled by the selection of fillers, which serve as bubble nucleating sites. The addition of quartz as a filler gready improves the flame retardancy of the foam char yields of >65% can be achieved. Because of its excellent dammabiUty characteristics, siUcone foam is used in building and constmction fire-stop systems and as pipe insulation in power plants. Typical physical properties of siUcone foam are Hsted in Table 10. 

Extruded Rigid Foa.m. In addition to low temperature thermal insulation, foamed PSs are used for insulation against ambient temperatures in the form of perimeter insulation and insulation under floors and in walls and roofs. The upside-down roof system has been patented (256), in which foamed plastic such as Styrofoam (Dow) plastic foam is appHed above the tar-paper vapor seal, thereby protecting the tar paper from extreme thermal stresses that cause cracking. The foam is covered with gravel or some other wear-resistant topping (see Roofing materials). 

Thermal insulation is available over a wide range of temperatures, from near absolute zero (-273 C) ( 59.4°F) to perhaps 3,(1()0°C (5,432°F). Applications include residential and commercial buildings, high- or low-temperature industrial processes, ground and air vehicles, and shipping containers. The materials and systems in use can be broadly characterized as air-filled fibrous or porous, cellular solids, closed-cell polymer foams containing a gas other than air, evacuated powder-filled panels, or reflective foil systems. 

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