Plastics & Polymerization: What Firefighters Need To Know

Plastics have been around for more than 100 years. The first plastic developed was cellulose nitrate, which was a replacement for ivory in billiard balls. Since World War II, however, the plastics industry has been one of the fastest developing...


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Plastics have been around for more than 100 years. The first plastic developed was cellulose nitrate, which was a replacement for ivory in billiard balls. Since World War II, however, the plastics industry has been one of the fastest developing technologies. The forms, variations and applications of plastics have developed at a tremendous rate, producing a family of materials that is unusually complicated and diverse.

Plastics are composed of organic materials that are part of a group of materials known as polymers. Polymers can be subdivided into two groups - naturally occurring and man-made. Common naturally occurring polymers include leather, wood, paper, silk, cotton and wool. Man-made polymers are created from organic materials found in nature. Approximately 53 billion pounds of synthetic polymers are manufactured each year in the United States alone.

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Photo by Robert Burke
The plastics used to manufacture automobiles generate thick, black smoke.

The American Society for Testing Materials (ASTM) defines a plastic as "a material that contains as an essential ingredient one or more organic polymeric substances of large molecular weight, is solid in its finished state, and at some stage in its manufacture or processing into finished articles can be shaped by flow."

The word polymer comes from the Greek "poly" (many) and "mer" (part). Therefore, a polymer is a compound with many parts. In reality, a polymer is a long-chained molecule composed of many smaller parts called monomers ("mono" is Greek for one). Monomers, however, are able to hook together into long chains of hundreds or thousands of parts. Such hooking is called polymerization.

In polymerization, monomers - which have double bonds - are broken down by heat or chemical reaction to single bonds. The single bonds attach to each other creating the self-reaction, which in turn creates the long chained polymer. This reaction usually takes place in a reactor vessel in a chemical plant under controlled conditions. But it can also take place during transportation or in storage, creating a hazard for emergency responders.

Man-made and naturally occurring polymers behave much the same way during reactions, especially when exposed to fire. In fact, some synthetic polymers contain the same elements as natural polymers, exhibit the same burning characteristics, and produce the same products of combustion - many of which can be toxic.

Naturally occurring polymers are standard in their identities - wood, for example, is not mistaken for cotton or wool. Synthetic polymers, however, are produced to conform to specific properties, and it may be difficult to distinguish between them. For example, polypropylene and polyethylene are very similar, as are styrene and styrene-acrylonitrile.

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Photo by Robert Burke
Much of the EMS and hazmat-response equipment used by firefighters are made of plastic or packaged in plastic.

Many terms are interchangeable when referring to synthetic polymers. The terms plastic, polymer, resin, compound and high-polymer macromolecular substance are used often used interchangeably.

Plastics are such a common part of our everyday lives that we don't give them much thought. They are found everywhere. Look around the room you are in - how many things are made of natural polymers and how many are synthetic?

As I type this column on my computer, I see that the housings for the computer as well as the keyboard, printer and monitor are made of plastic; the table the computer sits on is plastic; the chair I am sitting on is largely made of plastic and plastic fibers; the carpeting on the floor is made from plastic fibers; the telephone on the table is plastic; the cabinets next to the computer look like wood, but are actually plastic; the list could go on and on.

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