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Saturday, November 15, 2008

intro on Polystyrene

I know is a bit boring.....bt i still think its important to post it out.......

What is polystyrene

Polystyrene is a petroleum-based plastic made from the styrene monomer. Most people know it under the name Styrofoam, which is actually the trade name of a polystyrene foam product used for housing insulation. Polystyrene is a light-weight material, about 95% air, with very good insulation properties and is used in all types of products from cups that keep your beverages hot or cold to packaging material that keep your computers safe during shipping. Polystyrene is a thermoplastic substance, normally existing in solid state at room temperature, but melting if heated (for molding or extrusion), and becoming solid again when cooling off.

History
---discovered in 1839 by Eduard Simon, an apothecary in Berlin,from storax,
---1845 chemically identical as Styroloxyd
---1866 Marcelin Berthelot correctly identified the formation of metastyrol from styrol as a polymerization, process.
---thesis of German organic chemist Hermann Staudinger (1881–1965,leading to the substance receiving its present name, polystyrene.
---In 1959, the Koppers Company in Pittsburgh, Pennsylvania, developed expanded polystyrene (EPS) foam. Edward J. Stove made the first commercial foam cup. Experimental cups were first made of puffed rice glued together to form a cup to show how it would feel and look.The chemistry was then developed to make the cups commercial.

Structure and properties
---long chain hydrocarbon with every other carbon connected to a phenyl group (the name given to the aromatic ring benzene, when bonded to complex carbon substituents), (C8H9)n;
---contains the chemical elements carbon and hydrogen.
---a macromolecule

Use of polystyrene
Solid polystyrene is used to make disposable cutlery, yogurt and cottage cheese containers, cups, clear salad bar containers and video and audiocassette housings.
Schools, hospitals, nursing homes, supermarkets, restaurants and sports stadiums are among the many institutions and businesses that rely on polystyrene packaging.
Grocery stores use polystyrene in virtually all meat and poultry trays. In addition, polystyrene packaging can be found in egg cartons and a variety of produce packages, such as apple trays, mushroom tills, tomato containers, and strawberry and grape crates.
Polystyrene food service products are generally more economical to use than disposable paperboard products and reusable food service items.
The wholesale price of polystyrene disposable food service products is often approximately two to three times less than an equivalent disposable paper container, and four to five times less than a comparable reusable food service item when the costs of equipment, labour, water, electricity, and detergent costs are included.

Harm n beneficial
---Polystyrene does not biodegrade and resist to photolysis. It crumbles into fragments that do not break down
---its light and is often abundant in the outdoor environment
---The majority of polystyrene products are not recycled because of a lack of suitable recycling facilities. polystyrene "recycling" is not a closed loop, producing more polystyrene; polystyrene cups and other packaging materials are instead usually used as fillers in other plastics, or in other items that cannot themselves be recycled and are thrown away.Food service polystyrene packaging is not recycled because it is not economically viable due to contamination.
---Polystyrene takes up more space in landfills than paper and eventually will re-enter the environment when landfills are breached by water or mechanical forces.
---Polystyrene is not currently collected though kerbside recycling (some country manage to collect and recycle the polystyrene, but it just limited to some types of polystyrene.
---polystyrene deplete the ozone layer.
Initially a portion of polystyrene production was aided by the use of chlorofluorocarbons (CFCs), the chemicals that break down ozone in the troposphere. When this issue came to light, polystyrene manufacturers negotiated a gradual phase-out of CFCs in the production process and no CFCs have been used since the late 1980's.
Though polystyrene manufacturers claim that their products are "ozone-friendly" or free of CFCs, this is only partially true. Some polystyrene is now manufactured with HCFC-22, which, though less destructive than its chemical cousins, CFC-11 and CFC-12, is still a greenhouse gas and harmful to the ozone layer. In fact, according to a 1992 study by the Institute for Energy and Environmental Research, HCFCs are three to five times more destructive to the ozone layer than previously believed.
-"Study Finds CFC Alternatives More Damaging Than Believed," The Washington Post, December 10, 1989.
---unpolymerized styrene may pose health risks. Nevertheless, the EPA(environment ppolicy of America) states:

“ Styrene is primarily used in the production of polystyrene plastics and resins. Acute (short-term) exposure to styrene in humans results in mucous membrane and eye irritation, and gastrointestinal effects. Chronic (long-term) exposure to styrene in humans results in effects on the central nervous system (CNS), such as headache, fatigue, weakness, and depression, CSN dysfunction, hearing loss, and peripheral neuropathy. Human studies are inconclusive on the reproductive and developmental effects of styrene; several studies did not report an increase in developmental effects in women who worked in the plastics industry, while an increased frequency of spontaneous abortions and decreased frequency of births were reported in another study. Several epidemiologic studies suggest there may be an association between styrene exposure and an increased risk of leukemia and lymphoma. However, the evidence is inconclusive due to confounding factors. EPA has not given a formal carcinogen classification to styrene. ”



Kindly thankz for
http://www.earthresource.org/campaigns/capp/capp-styrofoam.html
Wikipedia

6 comments:

小杰 said...

wow...so complicated, that's y i hate chemistry.

Akira 思胜 said...

That's why we need to carry out 3R Project... Reduce, Reuse and Recycle...

Jeff 乙峰 said...

wah!!run!!

lock said...

i like your info, thanks for sharing!

save the environment, we should stop using styrofoam!

tom said...

小杰:complecated??wont lal.i adi shortcut it,nt being so scientifically(tell u sumting, i like organic chem,bt hate physical chem),bt now no nid study chem anymore......

Akira 思胜 :yay, and styroform goes to reduce .....REDUCE THE USAGE....

Jeff:Dun run so fast,wait u may fall down and catch u bc..(hehe)

lock:thank u,yaya, its too scary......

Bell's said...

Just get to know that USM had banned polysterene, but i remember my friend was studied about polysterene @ USM??

eerm....but somehow polysterene was really an environment killer..

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