From Dinosaurs to Plastic

A Simplified Description of the Origin of Plastics

By Jayme R. Leita, Senior Chemical Engineer, Eastman Chemical Company

Plastic is everywhere. From your alarm clock to your toothbrush, plastic plays many vital roles in everyday life.

Plastic’s multifunctional properties enable it to be used in everything from automobiles to vinyl siding, spaceships to prosthetic limbs, artificial turf to tableware and from bullet proof vests to credit cards; the list goes on and on.

So, what is plastic and where does it come from? The answers require a little bit of science.

In their most basic sense, plastics are made by joining together many small units, or monomers, of hydrogen and carbon into long chains known as polymers. Although primarily made up of hydrogen and carbon, polymers often contain additional molecules such as chlorine, fluorine or nitrogen that help give plastics their unique characteristics. For example, the plastic we call nylon contains nitrogen molecules. Polyvinyl chloride, or PVC plastic, contains chlorine. Scientists and engineers can build plastics with a variety of properties simply by fusing together different combinations of molecules into polymer chains.

We have established that plastics are made of long chains of monomers known as polymers. Now, where do these monomers come from? The monomers that make up polymers are converted from fossil fuels such as natural gas and crude oil. For millions of years, plants and prehistoric animals, like dinosaurs, died and decayed. Their organic remains were absorbed by the earth, layer upon layer. As the Earth shifted and changed, the organic layers were covered by thousands of feet of sand and silt, exposing them to very high pressures and temperatures. These extreme conditions helped transform the prehistoric remains into fossil fuels such as natural gas and crude oil, which are primarily complex mixtures of hydrogen and carbon.

The production of plastic from fossil fuels begins by exposing natural gas and crude oil to extreme heat, splitting the complex mixture of hydrogen and carbon into lighter, smaller molecules. As the conversion process continues, more heat is applied, producing an array of unique monomers such as ethylene, propylene, vinyl chloride and ethylene glycol.

Plastics are also derived from natural cellulose. Natural cellulose is one of the most diffuse organic substances in nature. Wood, paper and cotton all contain cellulose. One plastic, cellulose nitrate, is used as a replacement for ivory in billiard balls and was also used as a composite material for safety glass. Another plastic, cellulose acetate, is used in photographic film. Rayon, whose chemical name is cellulose xanthate, is used in clothing fibers as an alternative for expensive silk.

Whether derived from nature or synthetically produced from fossil fuels, some polymers must be enhanced in order to create a viable commercial product. To develop plastic as a material of choice, polymer chains are treated with additives that alter or improve specific properties. Additives serve to protect polymers from degradation and enhance their basic characteristics. Plasticizers, for example, are materials incorporated into certain plastics to increase flexibility. By strategically piecing together monomers along with functional additives, plastics can be tailored to specific design and performance requirements. It is this high level of customization that has empowered plastics to infiltrate a variety of industries across the market spectrum.

Once plastics have been tailored to meet customer specifications, they are generally supplied from the primary manufacturer to the customer in the form of small pellets or beads. The pellets must be melted and formed into desired end-products such as car bumpers, refrigerators, electronic enclosures, lipstick tubes and TV dinner containers. There are several plastic forming methods used today, however, extrusion, injection molding, blow molding and rotational molding are among the most popular.

Although plastics demonstrate specific characteristics which help distinguish them from one another, most plastics share general attributes. Plastics are very resistant to a variety of chemicals. From plastic wire coverings which protect you from electrical shock to thermal underwear made from polypropylene to keep you toasty in the winter, plastics act as both thermal and electrical insulators. Plastics are also light-weight materials offering varying degrees of strength and can be processed by a variety of methods to meet very specific functional needs for consumers. Due to the light weight and reusability of plastics, they provide cost-effective solutions to product manufacturers around the world. According to the America Plastics Council, American product manufacturers save enough energy each year to power a city of one million homes for three years simply by using plastic in their packaging.

From tough to flexible, clear to colorful, translucent to opaque, odor-free to aromatic and strong to flimsy, plastics’ versatility is celebrated in the quality and diversity of its characteristics. They can be chemically resistant, long-lasting, resilient and affordable. Polymer science is exploding with new possibilities for plastics everyday. Just as the remains of primitive plants and animals gave birth to the building blocks of plastics, design breakthroughs and technological advances will conceive the plastics applications of the future.