Discovery Science: Chemistry – Organic and Biochemistry – Plastics

Earth Science: Chemistry – Organic and Biochemistry – Plastics

Plastics are cheap and easy to process. The almost endless list of plastic products includes upholstered furniture, lacquers and paint, DVDs, casings of household appliances, and air bags in cars.

Due to their low cost, plastics are often used for single use products; however, because many are not biodegradable, they fill trash dumps and create a pervasive litter problem. Society needs to utilize more recycled and biodegradable plastics to avoid future enviromental problems.

In many ways, plastics have influenced the very fabric of modern society, from the decrease in glass bottles, wine corks, and Bakelite to the their role in the empowerment of women
through Tupperware parties in the 1950s.


Plastics are built up from thousands of small groups of atoms bound together into a large macromolecule. They are known as polymers: a term derived from the Greek words poly (“multiple”) and meros (“parts”). Thermoplastics soften and become moldable when they are warmed, while thermosetting plastics do not soften when heated; they change color or generally decompose.

The most important thermosetting plastics are synthetic resins used for iacquers. Elastomers can be deformed at room temperature using pressure or tension but will return to their original shape once the pressure or tension is released. Foam materials and polyesters are elastomers.

Light and moldable

Plastics have significant advantages over materials such as wood or metal. They are light in weight and resist damage from weather and chemicals. They are excellent insulators for heat and electrical currents. Further-more, they can be shaped easily. One widely used shaping technique is injection molding.

In this process, thermoplastic granules are melted and then injected into the hollow mold. The mold determines the form and surface of the finished product. Many plastic bottles are made using injection molding. Because of their wide use in short- lived products, plastics are a growing disposal problem.

The initial advantage of chemical stability later becomes a disadvantage, since they decompose very slowly in trash dumps and cluttered roadways, where they end up. Thus the issue of plastic recycling is growing in importance.

In the future?

PPV foils made from advanced plastics show promise as a new and flexible light source.

Electronic paper made from a thin and flexible screen of plastic foils could replace ink and paper, using electronic ink for text that changes upon the influence of an electric current.


Polycarbonate CDs. CD-ROMs, and DVDs are used today in numbers so large it is difficult to imagine. The 35 billion discs produced in 2001 would create a tower about 19,000 miles (30.000 km) high if the discs were stacked on top of one another.

Bottles, MP3 players, and sunglasses are also made of this useful thermo-plastic. Polycarbonates are widely used because they are transparent, inherently stable, mechanically firm, resistant to light, and easy to clean.


PVC (POLYVINYL CHLORIDE) is com monly used in many applications. How ever, it is very costly to recycle and is often included in ordinary rubbish leading to many countries developing detailed recycling systems to deal with plastics.


MOST PLASTICS melt when heated. This is because their threadlike molecular chains are held together only by weak molecular forces. Non plastics such as rubber can withstand higher temperatures.