How are Plastics Produced?

Michael Anissimov
Michael Anissimov
Michael Anissimov
Michael Anissimov
Plastic pellets, which are melted down to make other products.
Plastic pellets, which are melted down to make other products.

Plastic is the most versatile and widely used synthetic material on the market today. They are polymers, that is, large molecules (molecular weight ~10,000+) which consist of long repeating chains of smaller molecules (molecular weight ~100) known as monomers. Common monomers used in the production of plastics, such as vinyl acetate, styrene, butadiene and vinyl chloride, are extracted from crude oil or natural gas. Monomers fall into the class of chemicals known as petrochemicals.

A plastic food storage container.
A plastic food storage container.

Plastics are produced using a process called polymerization, where many thousands of monomers are joined together to form a polymer chain. Monomers are made of atoms like chlorine, nitrogen, oxygen, hydrogen and sulphur. Monomers are easily extracted from abundant organic sources, though as the price of crude oil increases, so does the price of plastics.

An old telephone made out of Bakelite®, a type of plastic.
An old telephone made out of Bakelite®, a type of plastic.

There are two main types of plastic; thermosetting plastics and thermoplastics. Both are produced by pouring liquid monomers into a mold where they undergo polymerization. Thermosetting plastics are permanent once molded — they do not deform under heat. Thermoplastics will melt under heat and can be reformed repeatedly. The polymerization process increases the molecular weight of the constituent molecules, turning liquid monomers into solid polymers. (Increase of molecular weight causes the substance to undergo a phase change.)

A pan coated with Teflon®, a type of plastic.
A pan coated with Teflon®, a type of plastic.

During the molding process, the monomer soup is superheated and condensed under many atmospheres-worth of pressure. This causes polymerization to occur and ensures that the plastic is solid and uniform, lacking any internal air bubbles (a big problem which had to be circumvented in the early days of plastics). The result is a finished plastic product. Well-known plastics include Bakelite®, nylon, PVC, synthetic rubber, acrylic, polyethylene (Tupperware®), Formica®, and Teflon®. The downside of their plastics is their impact on the environment. They take many thousands (or even millions) of years to biodegrade. In recent decades, the recycling of plastics has been encouraged, though only about 5% of plastics in the US today are actually recycled.

Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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    • Plastic pellets, which are melted down to make other products.
      Plastic pellets, which are melted down to make other products.
    • A plastic food storage container.
      A plastic food storage container.
    • An old telephone made out of Bakelite®, a type of plastic.
      An old telephone made out of Bakelite®, a type of plastic.
    • A pan coated with Teflon®, a type of plastic.
      A pan coated with Teflon®, a type of plastic.