"What is Chemistry Good For?"

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Please respond before 5 AM, Monday, September 25th, 2000.


Chemistry is Good for Making Materials
The Stoichiometry of Carpet Formation

If you want things, you have to build them. In ancient times, people used what was readily available around them, like rocks, trees and mud. Gradually over the years, humans have gotten increasingly adept at taking control of their environment and squeezing new, better materials with which to build things.

Once when I was camping with a bunch of other chemists, we met a group of campers from Northern California. After a few friendly words about the weather and the beauty of the Sierra Mountains, they asked us what we did for a living. Shockingly, when we said that we were chemists, they flat out told us that we were NOT WELCOME. They seriously did not want to associate with the types of people who were polluting the earth.



Once our shock subsided, we asked them what their tent was made of? They had a very high quality nylon tent that they were very proud of. We asked them how they purify their water. Like many other hikers, they carried a membrane filtration system and had iodine tablets as a back up. After we asked them what their pants were made from, they got the picture. Gore-tex is not a natural fiber either. These chemist-hating campers were depending on evil chemists to provide most of their supplies and equipment. Because of the work of chemists and chemical engineers, these hikers had tastier food and lighter, more durable equipment.


So what does all this have to do with carpet? I used to think that all carpet was either wool or cotton. Most is not! What is carpet made from? Where does it come from? How much is bought and sold each year in the US? Right now, the most common carpet is made from nylon fibers, which are durable and cheap. The annual world production of nylon is 2800 million pounds. Yes, 2800 million pounds! Since nylon is not a natural substance, it must be synthesized from somewhere. Because of limitations posed by the law of conservation of mass, if you need to make 2800 million pounds of nylon, you need to start with at least 2800 million pounds of something else. That something else is petroleum oil, which was originally pumped out of the ground.




Starting from the end and working forward, here is the process. Nylon chips are melted and forced through holes in a metal disk called a spinneret. The rate at which the nylon is forced through the spinneret and drawn out controls the diameter of the fibers. Prior to the spinning of the fibers, nylon is obtained as a tough ivory-like substance from the reaction of adipic acid and hexamethylene diamine. Both of these chemicals have functional groups (sites of potential reactivity) on both ends. Wallace Carothers of DuPont discovered that the reaction of these two molecules resulted in very long molecules. The amine groups (NH2) on hexamethylene diamine react with the acid groups (COOH) on the adipic acid just like the C terminus of an amino acid reacts with the N terminus of an amino acid to form the peptide bonds of proteins. A single reaction between adipic acid and hexamethylene diamine is shown below. It is possible to add another adipic acid to the end of every hexamethylene diamine and to add another hexamethylene to every adipic acid. In this way, infinitely long molecular chains are possible. To insure that good nylon is formed, the water byproduct must be removed from the reaction.

In the industrial nations, 2620 million pounds of hexamethylene diamine are produced each year. It is synthesized by a variety of routes, one being the hydrocyanation of butadiene to form adiponitrile. This process uses extremely toxic hydrogen cyanide gas. To minimize risks associated with the storage and handling of hydrogen cyanide, engineers have developed a process that uses the hydrogen cyanide immediately after it is generated.

And here are a few good links to get you started.

1. 2. 3. 4.

Research Questions (You will receive 1 point of extra credit for each correct answer up to a total of two points for this assignment)

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    These questions can be answered by exploring the links provided to you above.
  1. Which of the above chemicals (other than DHMO) is used in food products. Which food product in particular is it used in?
  2. Why is hydrogen cyanide also called Prussic Acid?
  3. What materials would you not want to make Berber carpet from? What is it normally made from?
  4. Who discovered nylon? What company did he work for?



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