No_2_August_1963 — Page 108

L.

▲ Figure 2-Applying plaster on to the foam layer. ▲ Figure 3—Close-up view of the foam applied around

etc. and does not readily propagate a flame.

In addition. it may be applied in the form of slabs. cut or shaped to any size. or it may be produced in situ. enabling cavities to be filled or surfaces to be sprayed with rigid foam.

In the new building. rigid urethane foam was applied in three different ways to provide insulation in three types of construction. The foam was sprayed on to the main walls, pre- formed slabs of foam were used under the concrete sub-floor and on the roof, and panels of foam with an exterior facing of ceramic tiles were used in the main entrance hall.

Wall Insulation

The interior surface of the cavity wall was given a straightening coat of plaster in the normal way and then sprayed with a urethane foam

102

a window opening, showing the foam. thickness and the untreated plaster.

composition prepared from the polyether resin Daltolac 41 and the organic isocyanate Suprasec D to give a layer of approximately 1- in, thickness. A finishing coat of conventional plaster was then ap plied over the foam. The rate of application of the foam (approxima tely 6 lb/min and the overall den- sity of the foam (approximately 3 Ib/cu. ft) were such that a wall sur face 10 ft x 8 ft was coated with foam in approximately 1-2 minutes. Under these conditions an insulating layer with a K value of 0.23 (B.t.u./ft2/h/°F. in.) was produced. (Lower K values may be obtained by use of special spray formulations incorporating Areton 11.)

Figures 1 and 2 show the techni- que of application. with the window openings masked by "Visqueen" sheeting (Figure 1). and the foam- coated surface being subsequently plastered (Figure 2). To ensure ade

quate adhesion between the finishing plaster and the foam. the latter was primed with a layer of a polyvinyl acetate emulsion (Bedacryl 388). Figure 3 shows the thickness of the applied foam.

One effect of the incorporation of the foam is clearly demonstrated in Figure 7. The wall on the right of the picture contains a foam layer under the plaster. The wall at right angles to it on the left also an out- side wall is not treated with foam. The marked thermal patterning of the latter over a period of 18 months contrasts markedly with the clean ap pearance of the foam-treated wall.

Water Resistance

Rigid urethane foams have a number of other valuable properties important in building applications. They are completely closed cell systems with a high resistance to penetration by water. A number of

THE HONG KONG & FAR EAST BUILDER-VOLUME 18. NUMBER 2