Biodegradable polymers were developed several
decades ago, but have been slow to reach commercial
maturity. Growth rate of bio degradable polymers
is slower because they are higher in costs and have
less robust physical properties than conventional
plastics. Insufficient incentives for downstream
processors to incorporate biodegradable materials
into their products, at least until the 1990s, have
also been an important factor contributing to their
slow growth.
However, things are changing. New large-scale production
systems are bringing down the costs of biodegradable
polymers, and sophisticated polymerization and blending
techniques are making such materials stronger and
more durable. In addition, food and beverage producers,
seeking goodwill from an increasingly environmentally
conscious public, have begun to employ biodegradable
plastics for a variety of packaging applications.
In some cases, local and national laws are also
encouraging the use of degradable materials.
Biodegradable polymers, especially those derived
from biological sources, are a minor factor in the
world plastics market. A recent report on bio-based
degradable polymers concluded that these materials
would have a 1-2% market share of all polymers in
Europe by 2010, and estimated no more than a 5%
share by 2020.
Food packaging is among the leading applications
of biodegradable plastics. Containers, films and
foams made of these materials are used to enclose
meats, dairy products, baked goods and produce.
Disposable bottles and cups for water, milk, juices
and beverages are other common uses. The other major
market is for plates, bowls and trays. Bags for
collection and composting of food waste, as well
as supermarket bags, are other outlets for these
materials. Agricultural films are a growing application
for these products
Unlike most other plastics, biodegradable polymers
can be broken down in the environment by micro organisms
such as bacteria and fungi. A polymer is usually
considered biodegradable if all its mass breaks
down in soil or water within 6 months. In many cases,
the degradation products are carbon dioxide and
water. Any other breakdown products or residue must
be tested for toxicity and safety.
Biodegradable plastics can be made from renewable
resources, such as corn-derived sugars, or they
may be made from petrochemical feedstocks. They
may be used alone or in combination with other plastic
resins or additives. Biodegradable polymers can
be processed with most standard plastics fabricating
technologies, including thermoforming, extrusion,
injection molding and blow molding.
Most biodegradable plastics belong to the polyester
class, although a few are made of other materials
such as modified starch. While aromatic polyesters
such as PET have good mechanical properties, they
tend to be resistant to microbial attack. Aliphatic
polyesters, on the other hand, are more easily degraded,
but are not as strong as their aromatic counterparts.
To improve the physical properties of degradable
aliphatic polyesters, developers have sometimes
added other monomers - either aliphatic or aromatic
- to their molecular chains.
Some of the common biodegradable polymers are:
· Polyhydroxyalkanoates (PHAs)
· Polylactic Acid (PLA)
· Synthetic aliphatic polyester
· Modified PET
· Modified starch
Biodegradable polymers are advancing on many fronts,
but are unlikely to constitute more than a small
fraction of the total plastics market in the near
future. However, growing environmental awareness
by consumers, and government policies that favor
conservation of natural resources are encouraging
sales of biodegradable polymers. In particular the
growing popularity of "green" packaging
offers many opportunities for innovation and market
growth.
(Based
on a report by the European Commission's Institute
for Prospective Technological Studies)
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