Civil Engineering Reference
In-Depth Information
Sheeting foils and papers
Three plastics are used for sheeting: polyisobutyl, polyethylene and polyvinyl
chloride. Cellulose acetate is also usable, but is not produced for this particular
purpose.
Polyisobutyl sheeting is produced in thicknesses of 1-2 mm and used pri-
marily as damp-proofing for foundations. Polyethylene, the most-used plastic,
is the only one used for vapour barriers, either alone or as a coating on paper
sheeting. The sheeting is 0.025-0.2 mm thick. Polyvinyl chloride sheeting is not
as vapour-proof as polyethylene, but it is used when higher strength is
required.
Paper sheeting is made mainly of polyethylene and polypropylene and is used
as a membrane in bathroom floors and as external moisture-proofing on founda-
tion walls. The sheeting contains added stabilizers to increase its durability, and
other additives such as a fire retardant and colouring.
Polyisobutyl and polyvinyl chloride contain large amounts of plasticizer.
Paper plastics usually have fewer additives. Polyethylene foundation paper con-
tains carbon as a ultraviolet stabilizer.
Building goods
The most common plastic in this case is PVC, mostly used as gutters and drain-
pipes. These are coloured and usually stabilized with cadmium.
Mastics
Apart from linseed-oil-based putty, the mastics available on the market today are
plastic- or bitumen-based. A mastic has to fulfil the conditions of constant elas-
ticity and durability. The plastics usually used are polysulphide, silicone,
polyurethane, and various acrylic substances. The composition of these sub-
stances is complex and is usually based on at least five chemical substances with
at least eight different additives. Mastics often have pigment and fibres added,
usually fibreglass. Silicones are easy prey for mould in damp situations, and
often have organic tin compounds added, about 0.05 per cent of the mastic.
Polyurethane mastics contain 10-60 per cent phthalates. Plastics of polysulphide,
polyurethane and polyacrylates contain chlorinated hydrocarbons as fire retar-
dants and secondary plasticizers. Up to the end of the 1980s PCBs (polychloro
biphenyls) were an important part of mastics for sealing between modules in
prefabricated buildings.
Sealing strips
These are used mainly between the sheets of glass in windows and in window
and door reveals. Important plastics used in sealing strips include polyurethane,
polyamide, polyvinyl chloride, ethylene-propylene rubber, chloroprene rubber
