Foamed polyurethane panels

The market for foamed polyurethane panels was estimated (1996) as 2.3 million m2 in the UK, 7 million m2 in Germany and I 2 million m2 in Italy, of which only a small percentage, say 5%, are made by batch production using vertical or horizontal foaming. The majority are made on continuous foaming lamination lines by such companies as Hoesch (Germany), Elcom (Italy), Forges D'Haironville (France), Kingspan (UK) and Perfrisa (Spain).

Polyurethane and polyisocyanurate foams can be foamed in place during the production, by:

- continuous foaming;

- vertical pouring; or

- horizontal pouring.

Becker (I 968) gives more details of methods of in-place foam production and other detailed considerations for sandwich panel design. Profiled sheets of metal with polyisocyanurate backing are often produced on a continuous process (Fig. 6.14). Surfactants are necessary to ensure a closed cell and to maintain the quality of the foam (Fig. 6.15).

Although well-insulated buildings help to reduce energy consumption, and indirectly limit carbon dioxide emissions by decreasing the amount of heating they require, increasing concern over the potential effects on the ozone layer of CFC gases used as foaming agents has led to a review of the materials and their manufacturing processes, resulting in the Montreal Protocol. Now producers of foamed polyurethane offer foaming formulations containing blowing agents such as HCFCI41 b. Early use of carbon dioxide blowing agents to reduce the effects of CFCs caused problems due to temperature variations on flat panels. It was also more difficult to use cartoon dioxide blowing

fasteners

6.12 Detail of panel at Renault Centre.

fasteners mm x 926 mm y 75 mm foamed steel panels mm x 165 mm vertical cladding mullion

6.12 Detail of panel at Renault Centre.

6.1 3 Relative insulation performance of different core materials.

agents with polyisocyanurate foams, which had been introduced for their improved fire resistance.

Development work is still continuing on new foam formulations to improve the efficiency of the manufacturing process. One difficulty for the manufacturers of foamed panels in changing the foaming agents used is that these modifications can result in slower production rates and a slight reduction in thermal performance. In theory, panels with modified foamed cores would need to be thicker and therefore potentially more expensive. Inherent in the manufacture of continuous foamed panels is the need to control density to maintain compressive strength. In laminating sheet core materials, it is the adhesion between the core materials and the skins that gives the panel its strength. The bonding therefore has to be undertaken in conditions of strict quality control. In recent years, manufacturers have understood the importance of good bonding, and they now check the temperature, humidity and coat weight of the adhesive

6.14 Typical continuous foaming line.

during production as part of their BS 5750 quality management procedures. Following production, checks are made on the strength of the bond to the panel skin, and samples from each production run are tested to destruction.

Foamed panels can also be made by batch production on individual foaming lines (Fig. 6.16), but the most economic production is achieved using a continuously operating line foaming plant. On a continuous horizontal line, which can now produce high-quality panels at a speed of 7 m/s, there is no limit to the length of the panels other than that imposed by the means of transportation and the individual manufacturer's method of fixing and panel configuration. Panels can now be transported on articulated trailers up to 30 m long, and typically panels are 6-1 2 m long.The width of coils of metal has increased in

Storage components

Storage components

Flexible covering f ^v material top

Adjustable pinch rollers

Flexible covering f ^v material top

Oscillating pour head

Adjustable pinch rollers

Flexible covering material bottom

6.15 Diagram of continuous foaming process.

recent years, so that steel panels can now be produced up to I 300 mm wide and aluminium up to I 500 mm. Foamed panels produced in a vertical-injected foaming press are normally limited to 600 mm high to control the density of foam over the width of the panel

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