What is plastic?

Do you have a definition what plastic actually is? You know, i have a class and i have to write about plastic. Booooo

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  • 1 decade ago
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    Plastic covers a range of synthetic or semisynthetic polymerization products. They are composed of organic condensation or addition polymers and may contain other substances to improve performance or economics. There are few natural polymers generally considered to be "plastics". Plastics can be formed into objects or films or fibers. Their name is derived from the fact that many are malleable, having the property of plasticity.

    Plastic can be classified in many ways, but most commonly by their polymer backbone (polyvinyl chloride, polyethylene, polymethyl methacrylate and other acrylics, silicones, polyurethanes, etc.). Other classifications include thermoplastic thermoset, elastomer, engineering plastic, addition or condensation or polyaddition (depending polymerization method used), and glass transition temperature or Tg.

    Some plastics are partially crystalline and partially amorphous in molecular structure, giving them both a melting point (the temperature at which the attractive intermolecular forces are overcome) and one or more glass transitions (temperatures above which the extent of localized molecular is substantially increased). So-called semi-crystalline plastics include polyethylene, polypropylene, poly(vinyl chloride), polyamides (nylons), polyesters and some polyurethanes. Many plastics are completely amorphous, such as polystyrene and its copolymers, poly(methyl methacrylate), and all thermosets.

    Plastics are polymers: long chains of atoms bonded to one another. Common thermoplastics range from 20,000 to 500,000 in moleclar weight, while thermosets are assumed to have infinite molecular weight. These chains are made up of many repeating molecular units, known as "repeat units", derived from "monomers"; each polymer chain will have several 1000's of repeat units. The vast majority of plastics are composed of polymers of carbon and hydrogen alone or with oxygen, nitrogen, chlorine or sulfur in the backbone. (Some of commercial interest are silicon based.) The backbone is that part of the chain on the main "path" linking a large number of repeat units together. To vary the properties of plastics, both the repeat unit with different molecular groups "hanging" or "pendant" from the backbone, (usually they are "hung" as part of the monomers before linking monomers together to form the polymer chain). This customization by repeat unit's molecular structure has allowed plastics to become such an indispensable part of twenty first-century life by fine tuning the properties of the polymer.

    Molded plastic food replicas on display outside restaurant in Japan.People experimented with plastics based on natural polymers for centuries. In the nineteenth century they discovered plastics based on chemically modified natural polymers: Charles Goodyear discovered vulcanization of rubber (1839) and Alexander Parkes, English inventor (1813—1890) created the earliest form of plastic in 1855. He mixed pyroxylin, a partially nitrated form of cellulose (cellulose is the major component of plant cell walls), with alcohol and camphor. This produced a hard but flexible transparent material, which he called "Parkesine." The first plastic based on a synthetic polymer was made from phenol and formaldehyde, with the first viable and cheap synthesis methods invented by Leo Hendrik Baekeland in 1909, the product being known as Bakelite. Subsequently poly(vinyl chloride), polystyrene, polyethylene (polyethene), polypropylene (polypropene), polyamides (nylons), polyesters, acrylics, silicones, polyurethanes were amongst the many varieties of plastics developed and have great commercial success.

    The development of plastics has come from the use of natural materials (e.g., chewing gum, shellac) to the use of chemically modified natural materials (e.g., natural rubber, nitrocellulose, collagen) and finally to completely synthetic molecules (e.g., epoxy, poly(vinyl chloride), polyethylene).

    In 1959, Koppers Company in Pittsburgh, PA had a team that developed the expandable polystyrene foam cup. On this team was Edward J. Stoves who made the first commercial foam cup. The experimental cups were 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. The machinery, market, product and sales were necessary because such a device was unknown. Today, the cup is used throughout the world in countries desiring fast food, namely, the United States, Japan, Australia,and New Zealand. Freon was never used in the cups. As Stoves said, "We didn't know freon was bad for the ozone, but we knew it was not good for people so the cup never used freon to expand the beads."

    The foam cup can be buried, and it is totally stable such as is concrete and brick. No plastic film is required to protect the air and underground water. If it is burned with sufficient oxygen, the only chemicals generated are water and carbon dioxide. Burning a ton of cups results in less than 600 grams of ash. It can be recycled to make park benches, flower pots and toys.

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  • 1 decade ago

    basically is made mainly of carbon and hydrogen.

    You may note plastics have lots of "poly" names eg polystyrene, polythene, as we called them polymers that have made from smaller monomer units by various processes

    Also you may want to think of plastics as like cooked spagetti, they are long chains.

    . Eg to make polythene you have ethene and break the double carbon bonds and then they make long chains for ethenes we call polythene.

    We get a lot of out plastics from oil actually as its carbon based!!

    The different plastics are made up of different polymers so have different properties which we find highly useful.

    You can make casein plastic by heating milk and adding vinegar and separating the solid and then molding it (it doesn't smell nice, but its a plastic).

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  • Anonymous
    1 decade ago

    An organic polymer, such as polystyrene or polyethylene.

    http://en.wikipedia.org/wiki/Plastic

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  • 4 years ago

    You look not-plastic....more like real.

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