All three of the basic material types—metal
(aluminum), ceramic (glass), and polymer (polyester
plastic)—are used for carbonated beverage
containers (per the chapter-opening photographs
for this chapter).All of these materials are nontoxic
and unreactive with beverages. In addition, each
material has its pros and cons. For example, the
aluminum alloy is relatively strong (but easily
dented), is a very good barrier to the diffusion of
carbon dioxide, is easily recycled, beverages are
cooled rapidly, and labels may be painted onto its
surface. On the other hand, the cans are optically
opaque, and relatively expensive to produce. Glass
is impervious to the passage of carbon dioxide, is
a relatively inexpensive material, may be recycled,
but it cracks and fractures easily, and glass bottles
are relatively heavy. Whereas the plastic is relatively
strong, may be made optically transparent,
is inexpensive and lightweight, and is recyclable, it
is not as impervious to the passage of carbon dioxide
as the aluminum and glass. For example, you
may have noticed that beverages in aluminum and
glass containers retain their carbonization (i.e.,
“fizz”) for several years, whereas those in two-liter
plastic bottles “go flat” within a few months.