No_2_August_1963 — Page 109

K

Material

Rigid Urethane Foam

Factor (B.t.u./ft2/h/- "F.in.)

Density

1.5 lb/cu.

upwards

and

Water Chemical Absorption Resistance

Nil

Very good

MAIN PROPERTIES OF AVAILABLE THERMAL INSULANTS

0.23 (CO2-blown)

0.12-0.16

Useful Tempera- ture Range

Self-extinguishing Sub-zero up

to 200° F

Strength

High in relation to low density

t

Flammability

(Arcton 11

blown)

Phenol-Formaldehyde

0.24

1 to 4 lb/cu.ft Low

Good

Foam

Cellular Polyvinyl

Chloride

0.23

4-5 lb/cu. ft

Nil

Good

Expanded Polystyrene

0.20 to 0.29 +

1.7-2.5 lb/cu.ft

Low

Good

Does not add to

flammability of

1

Self-extinguishing Up to 300° F

Self-extinguishing Up to 110° F

Adequate in laminate

Fragile unless laminated

Up to 150°F

flameproof

Structure

Cork Board

Glass Wool

0.28

8 lb/cu.ft

Nil

Poor

0.24-0.29 +

0.75-2.00 lb/cu.ft

Nil

Can be flameproofed

Very good Flameproof

Up to 300° F

High structural strength

Up to 450° F |

(Resin bonded)

Asbestos Board

Balsa Wood

0.76

0.31-0.40

34-38 lb/cu.ft

5-14 lb/cu.ft.

Poor

Flameproof

Can be flameproofed

Up to 1200°F

: Up to 350°F

Concrete

1.80

30-65 lb/cu.ft

Low

Good

Flameproof

Very strong structurally (40-70)

Only used where

strength is important

tests have revealed that the maxi- mum water absorption is of the order of 1.5% by volume. The foams have excelleht resistance to acids. alkalis and mineral oils. The water vapour transmission coeffi cient of rigid foam is 0.5-1.0 perm (compared with. for example. 4 perms for cork of density 7 10 lb/cu. ft). Urethane materials as a low class have

rate of flame transmission and. when formulated with tri-beta-chloroethyl phosphate. self-extinguishing characteristics are conferred on the foamed products.

a

According to form or type.

Urethane foams can be considered mould-proof for all practical pur- poses.

Sandwich Panels

Figure 5 Rigid foam slabs in place during the installation of the concrete floor. ▼

mics

modified by the addition of Arcton 11. This is trichloromonofluorome- thane, an inert liquid that volatilizes during the chemical reaction be- tween Daltolac 41 and Suprasec D. thereby giving foams of lower density than those prepared from unmodified systems. Mixes of this type have good flow properties and this enables narrow cavities to be injected with a mix that expands to a rigid low-density material inte- grally bonded to the facing materi- als. Daltolac 41/Suprasec D/Arc- ton 11 foams have particularly good thermal insulation properties, a K value of 0.16 having been recorded

of a cut section

foam of This measure. density 2 lb/cu. ft. of

Although urethane foam. as ap- plied by spraying. has a tough sur. face skin, this is not strong enough to protect the foam from accidental damage. In the application describ ed above the foam was protected by a layer of plaster applied by con- ventional techniques. Many other such as wood. metal. materials

plastics and cera. make suitable facing materials. and when

any these is used it is usually more convenient to pre- pare the foam and surfacing ma- terial as

a pre- formed laminated panel. Panels of this type used to form the main entrance to

were

the building (Figure 4).

In making these panels the Dal- tolac 41/Supra- see D mix was

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

on

a

ment was made on cut blocks having all faces exposed, after ageing for 12 months. Under practical condi- tions. with the foam integrally bonded to a surface material, it is anticipated that the ageing effect, due to gas diffusion processes, will be much smaller. and a K value nearer the initial figure of 0.12 would be obtained.

The advantages of sandwich panels of this type for building operations are apparent. The panels are strong robust units, well able to stand rough handling and misuse during installation. They provide a very high degree of

some

103