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MATERIALS OF CONSTRUCTION
strong and have a good resistance to a wide range of chemicals. The mechanical strength
depends on the resin used; the form of the reinforcement (chopped mat or cloth); and the
ratio of resin to glass.
By using special techniques, in which the reinforcing glass fibres are wound on in the
form of a continuous filament, high strength can be obtained, and this method is used to
produce pressure vessels.
The polyester resins are resistant to dilute mineral acids, inorganic salts and many
solvents. They are less resistant to alkalies.
Glass-fibre-reinforced epoxy resins are also used for chemical plant but are more
expensive than the polyester resins. In general they are resistant to the same range of
chemicals as the polyesters, but are more resistant to alkalies.
The chemical resistance of GRP is dependent on the amount of glass reinforcement
used. High ratios of glass to resin give higher mechanical strength but generally lower
resistance to some chemicals. The design of chemical plant equipment in GRP is the
subject of a book by Malleson (1969); see also Shaddock (1971) and Baines (1984).

7.9.6. Rubber

Rubber, particularly in the form of linings for tanks and pipes, has been extensively used
in the chemical industry for many years. Natural rubber is most commonly used, because
of its good resistance to acids (except concentrated nitric) and alkalies. It is unsuitable
for use with most organic solvents.
Synthetic rubbers are also used for particular applications. Hypalon (trademark, E. I. du
Pont de Nemours) has a good resistance to strongly oxidising chemicals and can be used
with nitric acid. It is unsuitable for use with chlorinated solvents. Viton (trademark,
E. I. du Pont de Nemours) has a better resistance to solvents, including chlorinated
solvents, than other rubbers. Both Hypalon and Viton are expensive, compared with other
synthetic, and natural, rubbers.
The use of natural rubber lining is discussed by Saxman (1965), and the chemical
resistance of synthetic rubbers by Evans (1963).
Butt and Wright (1984) give an authoritative account of the application and uses of
rubber and plastics linings and coatings.

7.10. CERAMIC MATERIALS (SILICATE MATERIALS)

Ceramics are compounds of non-metallic elements and include the following materials
used for chemical plant:

Glass, the borosilicate glasses (hard glass).
Stoneware.
Acid-resistant bricks and tiles.
Refractory materials.
Cements and concrete.
Ceramic materials have a cross-linked structure and are therefore brittle.