Civil Engineering Reference
In-Depth Information
stability. PVC is the most used coating for architectural fabrics due to the reduced
cost, the easy weld ability (high frequency, hot air) and the range of colours
available. In addition, it can be easily painted or printed. In order to obtain a non-
stick, self-cleaning surface resistant to UV rays, PVC is generally combined with a
top-coating based on acryl, polyurethane (PU), polyvinyl
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fluoride (PVF) or poly-
vinylidene
fluoride (PVDF). PVC coatings, combined with adequate topcoats, have
a life span of more than 20 years.
In order to reduce the high environmental impacts related to the use of PVC, new
alternative coating are currently under development.
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2.1.2.2 Fluoropolymer Coatings
Despite the higher price,
fluoropolymer is the most common material for coatings
when there are requirements for particularly high resistance to UV radiation and to
chemical and biological corrosion. The range of
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fluoropolymer coatings is quite
wide and includes PVF, PVDF and ETFE.
Polytetra
uoroethylene (PTFE) is the strongest bond in organic chemistry and
the most used
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fluoropolymer coatings (PVF and PVDF are mainly used as top-
coatings for PVC. THV has been only recently used in combination with polyester
fabrics due to the extremely high resistance to corrosion. Its colour is always off-
white becoming almost white with UV radiation (Bayer
2010
).
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2.1.2.3 Silicone
Silicone is mainly used in combination with woven glass fabrics due to the high
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flexibility and light transmission. It is relatively cost effective and has excellent
characteristics of UV and
flame resistance. It is considered the most environmentally
sustainable coating with great potential for the future (Goldsmith
2013
).
Its principal drawback is that it tends to pick up airborne particles and dirt. In
recent years, new formulations have been developed to address this issue. The main
technical limit is represented by the seaming process which requires PTFE threads
or silicone adhesive tapes.
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2.1.2.4 Polyurethane
Thermoplastic polyurethane is a polymer composed of a chain of organic units
joined by urethane links. Compared with PVC it has higher properties in terms of
elasticity, transparency, and resistance to oil, grease and abrasion. Due to the rela-
tively high cost and the progressive yellowing,
its use is restricted to special
applications such as biogas plants and
flexible tanks. It is easy to weld and due to the
higher airtightness it is commonly used for pneumatic structures such as in
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atable
tents and boats.
