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What is Polyethylene Plastic?

A plastic bag made with polyethylene.
Polyethylene is a very strong plastic and can be found in bulletproof vests.
Polyethylene sheets are generally sold in rolls.
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  • Written By: L. Hepfer
  • Edited By: Bronwyn Harris
  • Last Modified Date: 21 November 2014
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Polyethylene plastic is an inexpensive plastic material that is chemically resistant and can be very durable. Polyethylene plastic comes in a low density form and a high density form. The low density form was discovered first, followed a few years later by the high density form.

Low density polyethylene plastic (LDPE) came about in 1933 when it was discovered by two scientists, Reginald Gibson and Eric Fawcett. LDPE is made from oil. It has less strength and exhibits more flexibility than high density polyethylene plastic.

LDPE was discovered by accident during an experiment conducted by Gibson and Fawcett. Once discovered, they began to process the polymer material, giving it the name "Polythene." Used for coating submarine cables, it played an important factor in the war efforts during that time, enhancing the performance of the submarines. Over the next few years other companies became licensed and were able to produce LDPE.

Films or packaging materials such as garbage bags or sandwich bags are produced by using LDPE. LDPE is used to manufacture dispensing bottles and various laboratory equipment. It is used to make general purpose containers, trays and food storage. Recycling is possible with this particular form of plastic but it loses some of its quality the second time around.

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It wasn't until 1951 that high density polyethylene plastic (HDPE) was discovered by two chemists, Paul Hogan and Robert Banks. Since LDPE wasn't the easiest to work with, they started to experiment. They soon discovered crystalline polypropylene through an experiment with high octane gasoline.

From there they found a way to manufacture crystalline polypropylene and HDPE. HDPE is made from petroleum and is considerably stronger than LDPE. HDPE can be welded and is often found in larger plastic items because of its strength and durability. One of the first things HDPE was used to make was the hula hoop.

HDPE can be found in folding tables and chairs, storage sheds and snowboard rails and boxes. Thicker pieces of plastic such as plumbing, automotive fittings and storage containers are produced by using HDPE. Certain HDPE containers can be used to store food and are considered dishwasher safe. HDPE can be recycled but, like LDPE, it also loses some of its quality the second time around.

Polyethylene plastic was discovered accidentally through experiments many years ago. It can now be found in just about everything we use in modern day life. It is one of the most popular plastics in the world.

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Discuss this Article

anon322786
Post 6

Can anyone explain the difference between High Density Polyethylene and phenolic molding compounds? Are they used the same way?

anon247250
Post 3

Would anyone know how Polyethylene plastics biodegrade?

B707
Post 2

@BoniJ - I don't know much about recycling plastic, but I'll tell you what I know. Have you ever used those water bottles that collapse when you hold them? Well, I know that usually, they only recycle a product once and they recycle (say plastic bottles) into something different.

I wonder if those collapsible bottles are recycled the right way?

Another problem with recycling plastic is the dyes on the bottles. In some recyling methods, they can't mix more than one kind of plastic together.

One improvement is the discovery of a way to recycle plastic that uses heat. You can put all kinds of plastic together, and then mix for a long time in big things that look like clothes dryers.

Most people are pretty good about recycling, so I guess we should all try harder.

BoniJ
Post 1

I try to recycle all the plastic I can - like plastic bottles, food containers, kid's toys and just anything made of plastic. I hope all the plastic things that are put in recycling are actually recyced and made into something useful.

I know that oil is used to make plastic, and I hope we aren't using too much of our oil to make plastic things.

I'd like to know more about recycling - how it is done, how much energy it takes and what they make from the old plastic. Anybody?

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