Shrinking Polymers!

Some plastics will shrink when you get them hot. Two of these are polystyrene, the material in foam cups and plastic food containers, and the other is polyester, from which soda bottles are made. You can make your own shrinking polymers by baking polystyrene in a regular oven! You will need a clear, disposable food container such as those that salads are sold in at fast food places - or the plastic containers used for cookies and cakes at the supermarket deli. You will also need sand paper, permanent markers or colored pencils, a cookie sheet, margarine or shortening, and A PARENT'S HELP!

1. A good way to know that you have the right kind of plastic containers is if they have a recycling number 6 and the letters "PS" on them. Clean the containers and then cut out the flat sections. These are the parts that will shrink the best. It's good if you have several containers, so you can make more shrinking polymer designs.
2. Use medium grit sand paper to rough one side of the plastic sheets. These are the sides that you will draw designs on, so they need to be sanded pretty well.
3. Once the sheets are sanded well, figure out what kinds of designs and shapes you would like to make out of them. Think of shapes that can be colored and cut out. Shapes like stars or flowers or cartoon characters work well. Then draw the designs on the rough side of your plastic with colored pencils or permanent marker. Be sure to draw the designs big because when you bake them they will shrink a lot.
4.Now carefully cut out the shapes you have drawn and colored. Grease a cookie sheet with shortening or margarine to keep your plastic designs from sticking. Then place them on the cookie sheet. Get your mom or dad to heat the oven to 350 degrees and then to help you bake your plastic shapes for 1 minute. If you have an oven with a window you can watch them shrink. They may curl up at first, but then as they shrink they will flatten out again. They will be one-third their original size and six times thicker than before!

Speaking of things that shrink -- did you ever wonder about shrink wrap? How do they get it around things?

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