Chance Discoveries: Polyethylene

Air Date: 10/19/2011
Source:
NBC Learn
Creator:
Ron Allen
Air/Publish Date:
10/19/2011
Event Date:
10/19/2011
Resource Type:
Science Explainer
Copyright:
NBCUniversal Media, LLC.
Copyright Date:
2011
Clip Length:
00:04:38

This NBC Learn video, part of a series on "Chance Discoveries" in chemistry, tells how three different chemists in two countries over more than 30 years happened to make a white, waxy substance during lab experiments that, once recognized as potentially useful and developed, became polyethylene -- the most common plastic in the world.


Chance Discoveries - Polyethylene

RON ALLEN, reporting

Take a look around. One material is constantly at your fingertips. From keyboards, to shopping bags, to water bottles, it's hard to imagine a world without plastic, specifically plastics made from a polymer called polyethylene.

MICHAL MEYER (Editor in Chief, Chemical Heritage): Polyethylene. That's the most common plastic in the world. You see it in absolutely everything. You see it in soft drinks, you see it in Tupperware. That's the plastic you're most likely to see in a day-to-day basis.

ALLEN: While plastic is common today, its discovery happened not once, not twice, but three times, and all by chance. The first time happened in 1899 by German chemist Hans von Pechmann, when he accidentally heated the yellow gas diazomethane. The reaction created a white, waxy substance. Instead of investigating further, von Pechmann shelved his results and moved on. So did two other German chemists, Eugen Bamberger and Friedrich Tschirner, who stumbled across that same white, waxy substance a year later by polymerizing ethylene gas. While they didn't do anything with the substance, the process they used, polymerization, would become instrumental in discovering plastic.

MEYER: To create plastics, you start off with what is called a monomer, which is a building block. And what you are doing is you're joining these monomers together, rather like a paper chain that you might be making for a party. You join them all together and you can make very, very long chains. And these chains are called polymers.

ALLEN: It wasn't until 1933 that British chemists Eric Fawcett and Reginald Gibson at the Imperial Chemicals Industries (ICI) came across this same white, waxy polymer and realized that it was worth more research.

MEYER: At this time, I.C.I. was interested in the effects of high pressure on certain organic compounds, including ethylene. And one of the experiments was putting ethylene together with benzaldehyde, and then putting that under pressure.

ALLEN: Something about the reaction caused the ethylene gas to polymerize.

MEYER: They ended up with this white, waxy stuff that they actually recognized was polyethylene. They realized that they had polymerized ethylene and created polyethylene.

ALLEN: Even though they successfully identified the substance, they could not reproduce their results. The chemists suspected an air leak in the lab equipment. After more testing with new equipment, another chemist at I.C.I., Michael Perrin, figured out that the leak was actually the solution: add oxygen.

MEYER: And what the oxygen did is it persuaded the monomers, the building blocks, to join together and actually create the polyethylene. So from then on, they could consistently create polyethylene whenever they wanted.

ALLEN: With the outbreak of World War II, ICI was approached with an immediate need for a cable insulator for ground and airborne radar equipment, something that would help the Allies track down German U-boats, adding to the war effort.

MEYER: Polyethylene was such a good insulator that it meant that the components could be made smaller than they could otherwise be made, which meant that radar became far more versatile and far more useful than it would initially have been if it had only been land-based radar. So in that sense, that was polyethylene's contribution to World War II.

ALLEN: The public had little knowledge of polyethylene until after the war, when manufacturers started to look for a consumer market. Because of the adaptable nature of the plastic, products could be made flexible or firm.

MEYER: It can be made into soft plastic water bottles. It can be made much more rigid. It also works as body armor. It's one of the most remarkably versatile plastics out there. And it's also incredibly cheap to produce.

ALLEN: So cheap, that more than 60 million tons of plastic and polyethylene are manufactured each year, making this chance discovery something that's very easy to find today.

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