Civil Engineering Reference
In-Depth Information
•
The energy crisis of the early 1970s resulted in an increase
in the cost of petroleum-based products. The
unpredictability of the sources of oil supplies meant that
the quality of asphalt was not consistent. This, in turn,
affected the quality of roofing materials.
•
Energy-induced inflation raised the cost of labor-intensive
BUR, thus making the alternatives economically more
viable.
•
Advances in polymer chemistry and technology resulted in
the development of many polymer-based synthetic materi-
als that could be used for roof coverings.
•
During the 1960s, new structural design principles gave
rise to lightweight structures that caused problems for
conventional roofing assemblies owing to their increased
structural movement.
•
Highly insulated roofs and decks with unusual architec-
tural configurations allowed innovative designs of roof
systems that only the new materials could meet.
•
The aesthetics of roofs in terms of color and pattern
presented the architect with attractive alternatives that
would complement the architecture of other elements,
like flooring and carpeting, in a building as well as other
exterior elements of the building.
• Better corrosion-resistant metals.
As a consequence, literally hundreds of new roofing materials have
appeared on the market. Most of them are polymeric in nature. They are
reinforced with a variety of woven and non-woven fabrics of synthetic and
glass fibers.
5.1
Polymers
In the field of polymer chemistry, there are many terms related to
internal structure such as monomers (as in EPDM), co-polymers as in
vinylidene chloride (Saran wrap), block co-polymers (as in SBS), and inter-
polymers (as in EIP), etc. Polymers are giant molecules of different chemi-
cals. A polymer or a macromolecule is made up of many (
poly
) molecules
