just put some Saran wrap on leftovers. Was it Saran or some cheaper
knock off? Does it matter? Probably not, since my family will eat it
tomorrow regardless (they are not picky). However, if you were packing a
product to be shipped around the world, like an expensive
pharmaceutical product or even an inexpensive snack, you would care.
Time is money - esp. when it is sitting on a store shelf.
does this relate to the esoteric term, nanocomposites? The cause of most
food spoilage is are either microbial or chemical- specifically
oxidation. Microbes are relatively large (micron sized), so plastic
films easily act as a barrier. A molecule of oxygen, however, is very
small (more than 1000 times smaller than a microbe) and can be
transported through plastics (also known as polymers) easily. This
transport or permeability depends on the solubility of oxygen (or how
well it dissolves) in the polymer and its ability to diffuse or move
through the polymer.
Different polymers have vastly different
gas transport properties and cheap polyethylene (Glad wrap) is much more
permeable to gases than polyvinylidene chloride (Saran wrap). However,
if you look at the packaging after you finish those chips from the
vending machine, you will see that they have an additional layer of
aluminum foil that really prevents gas transport.
has been found that when polymers are sequentially prepared into
nanometer thick layer cakes, the barrier properties of the materials
improve. Because polymers are glass-like structures, they tend to
change or relax over time. This relaxation basically allows the polymer
molecules to get closer together and this more compact structure blocks
the transport of gas through the material. So controlling the
nanostructure of polymer films could increase the shelf life of products
and potentially eliminate the need for the expensive aluminum layer in
More specifically, a composite in a combination of
materials. A polymer with nanosized additives would be called a
nanocomposite. Adding nanosized particles to polymers can increase its
strength, decrease its weight and improve its barrier properties (or how
well it blocks oxygen). The nanosized material could be relatively
inert clay materials or potentially antioxidant or antimicrobial
While many people think of packaging as either
something for marketing or something that is waste issue, and indeed
both are true, good packaging prevents food spoilage and protects the
activity of pharmaceutical products. Every day we pack a lunch, save
leftovers, open a container from the store. Whether we like it or not,
packaging is a part of our everyday lives.