Docstoc

Polystyrene_rrl

Document Sample
Polystyrene_rrl Powered By Docstoc
					Polystyrene


Polystyrene, an aromatic polymer, is synthesized from the aromatic monomer styrene
which comes from petroleum products. It is a thermoplastic substance that could be
solid in room temperature or liquid when melted. One of the most common forms and
uses of polystyrene is the EPS which stands for Expanded Polystyrene. The industry
manufactures such product by mixing polystyrene with blowing agents in the form of
carbon   dioxide    and   pentane        which    comprises     5%-10%    of    its   composition.
(http://en.wikipedia.org/wiki/Polystyrene). The EPS is also called foamed polystyrene
and it is said to be 30 times lighter than regular polystyrene. This substance is popularly
used     in   the     form         of    beverage        cups    and     insulating     materials.
(http://www.wq.uiuc.edu/Pubs/Styrofoam-2-15-05.pdf). The basic unit of polystyrene
which is styrene, which is a known neurotoxin and animal carcinogen, is considered
very harmful to human health. In fact, it inflicts neurological and hematological disorder
especially to factory workers. EPS food packaging is the one accountable for the
leaking out of styrene. Styrene leak or leech is triggered when acids from our juices
when placed in such EPS cups and when food with Vitamin A content is placed inside a
microwave      leading       the        styrene     to     accumulate      in     our     system.
(http://www.cawrecycles.org/issues/eps_health).


Polystyrene is in high demand. It is the most used and utilized thermoplastic in the
industry due to its durability. But it is not biodegradable. (Mor and Sivan, 2008).
According to the Californians Against Waste (CAW), it is very difficult to recycle due to
its light weight property, which accounts for why it’s expensive to recycle. Imagine just
recycling a ton of polystyrene, needs a budget of $3000. Hence, it has a negative scrap-
value. More so, it’s due to this light weight property that they find polystyrene hard to
transport since polystyrene is advised to be always kept food-free and uncontaminated
when recycled. The build-up of polystyrene in landfills, as reported by CAW, will
contribute to plastic marine debris, since even when it is disposed of properly it is
carried by natural agents such as wind or other forces to the ocean. As manifested,
there is an excess of it in the environment and it is a major pollutant. (Mor and Sivan,
2008). For almost three decades ago, polystyrene was first ban due to the utilization
CFC material for its generation. In fact there was a hype heralding that it is recyclable.
After some time the companies that invested for its recycling process disappeared. This
move confirms that, indeed, recycling polystyrene is not an easy thing to do. Now, the
problem is back and the attention of scientists is focused on the recycling of disposable
foamed polystyrene. But recycling it would cost much in terms of energy, waste and
management point of view. (http://www.cawrecycles.org/issues/epsban_summary). A
way of solving such impending problem, is through biodegradation (Mor and Sivan,
2008; Singh and Sharma, 2007).


Biodegradation has been manifested in a number of studies already. And some of the
studies will be named here. A study by Mor and Sivan (2008), dealt with the monitoring
of biofilm formation of the microbe Rhodococcus sp. strain C208 on polystyrene. Their
aim was to observe the kinetics of biofilm formation and of whether polystyrene would
be degraded. They used two methods in quantifying the biofilm biomas: modified crystal
violet staining and observation of the protein content of the biofilm. The C208 strain was
cultured in a flask containing polystyrene flakes with the addition of mineral oil (0.0055%
w/v), which induced more biofilm buil-up. The study concluded that after an extension of
8th weeks of incubation, loss of 0.8% (gravimetric weight loss) of polystyrene weight was
found. From this, Mor and Sivan (2008) regarded C208 to demonstrate a high affinity
towards polystyrene through biofilm formation which lead to it’s degradation. The C208
strain is a biofilm-producing actinomycete that has first colonized and degraded
polyethylene (Orr et al., 2004).


There were studies that tested the possibility of whether copolymerizing polystyrene
with other substance could make it more degradable and susceptible to microbial
attack. In 1992, a study by Milstein at el. (1992), focused on the biodegradation of a
lignin-polystyrene copolymer. The white rot basidiomycete was used to degrade such
lignin-polystyrene complex copolymer. Such fungi released enzyme that oxidized lignin
and demonstrated the degradation through weight loss, UV spectrophotometric analysis
and deterioration of surface of the plastic substance as seen under the SEM. A similar
study by Singh and Sharma (2007) demonstrated through the process of graft
copolymerization that polystyrene must be modified with natural polymers and
hydrophilic monomers so as to enhance its degrading ability and so as to render
polystyrene waste useful in diminishing metal ion pollution in water and. According to
the mentioned study, the degrading rate of polystyrene increased to 37% after
subjecting it to soil burial method for 160 days.


Furthermore, the study of Mota et al. (2007), explored the degradation of oxidized
polystyrene using the fungi Curvularia sp. After about nine weeks of incubation,
microscopic examination revealed that hyphae had grown on the polystyrene. The
colonization of the fungi and it’s adhesion to the surface of the substance, according to
Mota et al., is a crucial step towards polymer biodegradation.


As demonstrated, colonization is needed in determining whether a particular microbe or
organism is a potential biodegrading agent. (Mota et al., 2007) The growth of the
microbes on the surface of the polystyrene is a step that would lead to its degradation.
Further visual confirmation of deterioration of surface area is done by using the
scanning electron microscope. (Mor and Sivan, 2008; Mota et al., 2007 )

				
DOCUMENT INFO
Categories:
Tags:
Stats:
views:31
posted:3/1/2010
language:English
pages:3