Science

Please Pass the Science - Styrofoam
by Scott Berk

What would we do without styrofoam? How else could we host a party without having to clean out 58 cups afterwards? How else could we safely ship delicate electronic equipment or expensive glassware? Most importantly, how else could we keep the hot side of our McBLT hot and the cold side cold? Well, to be honest, there are tons of ways we can do all of these things without styrofoam, but styrofoam is cheap and people like it. Never mind that its manufacture may be significantly contributing to the destruction of the ozone layer. Who cares that we may all have to wear UV protective body-stockings in a few decades to avoid getting skin cancer! We need our packaging! Why should we change our quality of life, simply to insure the health and well-being of future generations? But, I digress ...
Like it or hate it, styrofoam is part of our lives. So just what is it, and why has it become the bane of environmentally conscious people everywhere? Well, let's start complicated and get simpler. Styrofoam is crosslinked polystyrene which is blown out using chlorofluorocarbons upon manufacture. Now, as a chemist, I can understand that perfectly. But to the uneducated masses, it may as well have been the fine print on a bottle of shampoo. Read on and be edified.
Polystyrene is a polymer, a chemical which is made up of simple repeating chemical units, called monomers (a knowledge of Greek prefixes goes a long way in the world of science). Other polymers include plastics, nylon, rubber, and even DNA, the molecule of life. In polystyrene, the repeating unit is called, surprisingly enough, styrene, and has the chemical structure shown below. Making polystyrene involves treating styrene in such a way that it attaches to itself. The process, called polymerization (another big surprise), produces long chains (see figure) made up of thousands of styrene units.
Polystyrene Structure
Polystyrene itself is just a random mass of long strands, and is not very useful. To give it strength and resistance, the polymer is crosslinked. Certain compounds are added to the styrene which can link two or more polymer strands together. This network of strands is much more versatile than the individual strands themselves. To understand how this can be, imagine the difference between a bunch of pieces of thread and a pair of pants. Which would you rather wear?
But the styrofoam story doesn't end with crosslinked polystyrene. Indeed, the most important and most controversial step is still needed to put the "foam" in styrofoam. As the polystyrene is being made, gases are blown into the mixture. This causes the polymer to foam up, forming the styrofoam that we all know and love. The environmental malaise comes from the use of chlorofluorocarbons (CFCs) as the so-called "blowing agents." Once the styrofoam is made, the CFCs diffuse out and are replaced by air. These CFCs then rise into the atmosphere, where they finally encounter and react with ozone, destroying it. And, as you might have heard, if the ozone layer is destroyed, the earth turns into one major tanning salon. A simple solution to the problem would be to stop using CFCs as blowing agents, but it seems that CFCs work the best and cost the least, two big pluses for an industry that, like all industries, relies on profits to stay in business. One can only hope that the problem will be solved soon, and global catastrophe can be averted.
In the meantime, there's nothing wrong with having a little fun with styrofoam, and learning a bit about the solubility properties of crosslinked polymers in the process.
***HERE'S WHAT YOU'LL NEED***

Styrofoam cups, dishes, or packaging (I especially like the "peanuts"!)

Acetone (While nail-polish remover works, pure acetone with no water
added is faster and much more impressive. Acetone is a universal organic solvent available at hardware stores or organic chemistry labs.)

Make a small puddle of acetone on a flat surface (work outside or in a well ventilated area). Place the styrofoam in the puddle. If you are using nail- polish remover, the styrofoam will slowly "melt" into the puddle. If you are using pure acetone, the styrofoam will sink into the puddle almost immediately, like the Wicked Witch of the West in "the Wizard of Oz." Since styrofoam is mostly empty space, you can add quite a bit to a small puddle. All that remains is a sticky residue. What causes this rather dramatic effect? When styrofoam is placed in acetone, the long polymer strands are dissolved, releasing the trapped air and causing the structure to disintegrate. However, the insoluble crosslinked parts of the polymer keep the polystyrene from dissolving entirely, in much the same way as buoys on nets keep the entire net from sinking to the bottom of a lake. Once the acetone evaporates, you are left with a hard crosslinked polystyrene residue. Try it! You don't have to be a scientist to appreciate it, and you don't need a degree to have a basic understanding of polymers and . . . SCIENCE!!!

Why is the sky blue? What is a quark? What is the true nature of the universe? Can I stain my roommate's teeth by adding something to their toothpaste? Send your burning questions to "Please Pass the Science" in care of this magazine.