Classify and Identify Different Polymers to Determine Their Physical Properties and Uses.

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Science 2010
EEI Science Report

Aim
Classify and identify different polymers to determine their physical properties and uses.

Background
Polymers are long chain molecules that are made up of repeating smaller chemical units called monomers. The terms polymer and monomer were derived from the Greek roots poly (many), mono (one) and meros (part). Polymers are commonly made up of the chemicals carbon and oxygen however some polymers also include oxygen, chlorine, fluorine, nitrogen, silicon, phosphorous, and sulfur. Polymers are made from monomers containing a double bond. A chemical reaction bonding monomers together to make a polymer is called polymerisation. A polymer can be formed in two ways. One formation is addition (a single product). This can be represented as A+A+A+A = A-A-A-A. Another formation is condensation. This occurs when a polymer and small molecule form, like water. There are both naturally occurring and synthetic polymers. Natural polymers include such things as tar and shellac. Synthetic polymers are produced commercially on a very large scale and have a wide range of properties and uses. The materials commonly called plastics are all synthetic polymers. All materials used in this experiment are synthetic.

Polymers are common in our everyday life – in DNA, in proteins and starch, in the wheels on skateboards and the tyres on bikes and cars. In fact, polymers can be found every day, everywhere in the world.

Polymers can be classified into two different groups. These two groups are thermoplastic polymers or thermosetting polymers. Thermoplastic polymers, when warmed, can reshape easily. The molecules of these polymers are tangled together. When they are heated, they slide past each other easily. An example of a thermoplastic polymer is an ice-cream container.

Polymers that burn and char when heated are called thermosetting polymers. The molecules of these polymers are cross-linked so they are held together more rigidly. This means that the polymer chains cannot slide past each other when they are heated. Materials such as the soles of tennis shoes and foam cups are examples of thermosetting polymers.

Polymers are useful because chemists can change their structure by changing the length of the molecular chain, changing the chemical composition of the monomer units, or by changing the way the monomer units are arranged. The length of the polymer chains and the presence or absence of cross-links between chains determines the physical and chemical properties of polymers.

Polystyrene is used to make many types of containers such as videocassette cases and compact disks cases, tableware (forks, knives and spoons), and cafeteria trays. A foamed form of polystyrene is used to make heat resistant coffee cups, grocery store meat trays, and building insulation. To minimize fumes in the laboratory, this procedure uses a styrene casting resin. Unexpanded polystyrene is commonly used in thermal insulation systems (wall, roof and sub-floor), ceiling panels and other decorative surfaces, pipe insulation, protective packaging, flotation and buoyancy applications. Polystyrene is commonly used because of its ability to be a lightweight and relatively strong thermal insulator. In the four experiments two types of polystyrene are tested – unexpanded polystyrene and expanded polystyrene.

Nylon was the result of research directed by Wallace Hume Carothers at du Pont. The research team was interested in duplicating the characteristics of silk. Nylon gained rapid acceptance for its use in stockings and in making parachutes. The success of nylon products led to the invention of rayon, dacron, orion, and polyester. Nylon contains nitrogen and oxygen. It is a lightweight flexible material. When bound with other pieces of nylon the strength of it increases.

Polyethylene is a plastic with a range of uses including food packaging and gas pipes. There are two types of polyethylene – high density...
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