What is plastic

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Science The controversial sale of 'Big John,' the world's largest Triceratops. Science Coronavirus Coverage How antivirals may change the course of the pandemic. Synthetic polymers include polyethylene used in plastic bags ; polystyrene used to make Styrofoam cups ; polypropylene used for fibers and bottles ; polyvinyl chloride used for food wrap, bottles, and drain pipe ; and polytetrafluoroethylene, or Teflon used for nonstick surfaces. Although many polymers are hydrocarbons that contain only carbon and hydrogen, other polymers may also contain oxygen, chlorine, fluorine, nitrogen, silicon, phosphorus, and sulfur.

Natural polymers, such as cellulose and latex, were first chemically modified in the 19th century to form celluloid and vulcanized rubber. The first totally synthetic polymer, Bakelite, was produced in The first semisynthetic fiber, rayon, was developed from cellulose in However, it was not until the global disruption caused by World War II, when natural sources of latex, wool, silk, and other materials became difficult to obtain, that synthetics were mass produced.

Synthetic rubber was needed for tires, and nylon was needed as a replacement for silk for parachutes. Today synthetic polymers in the form of plastics are in wide use, and the plastics industry is one of the fastest growing in the United States and around the world.

The industry produces approximately kilograms of polymers per person annually in the United States. Monomers can be chemically joined together in two ways: addition polymerization or condensation polymerization. Addition polymerization has three basic steps: initiation, propagation, and termination. Polyethylene, polystyrene, and acrylic are examples of plastics formed by addition polymerization.

These polymers are often thermoplastic in nature: they can be heated and made soft and then hardened when cooled. They are easily processed, reprocessed, or recycled. During condensation polymerization a small molecule is eliminated as the monomers join together. Nylons, some polyesters, and urethanes are examples of condensation polymers. These polymers can be thermoplastic or thermosetting. Although all plastics are in a liquid state at some point in processing and are solid in the finished state, once a thermoset polymer is formed, it cannot be melted and reformed.

The monomers in a polymer may be arranged in a variety of ways. The plastic must now be shaped into a useful product. This is done at a factory where the plastic is molded into shape by melting, shaping, and solidifying it. Generally, the plastic is softened, and then it is either injected into a mold, shaped over a mold, extruded through a die, or laminated. Each of these methods can be completed in different ways.

Some examples are ram extrusion, compression molding, injection molding, blow molding, or casting, to name a few. Finally, after the product has been shaped, it may undergo some finishing touches such as joining, machining, or coating. The result can be seen in the multitude of products found throughout your house.

It is even more important to consider this when you are looking at buying something new made of plastic. Essentially, plastics can be shaped and molded when heat or pressure is applied to them. Plastics are made of polymers, which in turn are made up of many, sometimes thousands, of monomers. These polymers give the plastic its properties. There are two main categories of plastics, thermoplastic and thermosets.

Thermoplastics can be melted repeatedly, while thermosets can no longer be melted once the initial product is created. These categories help determine if a particular plastic can be recycled or not. This can make identification and recycling difficult. To keep learning about plastics and plastic recycling by numbers check out the following articles. We all have a bunch of old keys lying around the house.

They may be from our last home, an old workplace, or a lock. How does Recycling Help The Environment. What does biodegradable mean? Here, we give you the facts, plus explain what it means for the environment and understand how to shop and recycle. What is America Recycles Day all about? Learn the benefits of recycling and how it helps our environment.

Find great tips and get involved. Plus receive regular tips on recycling and updates on great recycled products. We use cookies to ensure you get the best experience on our website. Learn more. What is Plastic? A simple explanation. Share with your friends on:. Share on facebook. Share on pinterest. Share on twitter. Share on linkedin. Below is what I learned. Quick Navigation. Think of all the different types of plastics you handle every day.

What are monomers? What are polymers? Types of Plastic. Thermoplastic vs. There are two main categories of plastics; they are thermoplastics and thermoset plastics.