The six main kinds of plastics may be identified through an analysis scheme that separates each one based on chemical and physical properties of density, reaction in a flame, reaction with acetone and reaction when heated. Known resins will be used first, followed by an assortment of everyday plastic items (drinking cups, butter or yogurt cups, lids, etc.).

Procedure:

Examine the pieces of plastic items in your bag. (Record which numbered bag you are given.) Try to group them by type (Recycle #1, 2, etc.) based on your notes off the Internet. DO NOT write on the pieces of plastic themselves, but arrange a small square of each one on numbered sections in your lab book. You will later test a small sample of each piece in the same way that you test the known resins and then compare your predictions with the results of your tests. Note, also, the texture, gloss or shine, color, flexibility, transparency, odor, etc.

You will be given 10 pieces of each known resin. Follow the analysis scheme shown below to see how each type of plastic can be identified. You will want to record the following information:

pellet color
water test results
other test results (you may make a table in which to record this information)

Then cut off a small piece from each of your unknown samples and carry them through the same scheme recording the same information and identify them as to recycle type.

Discussion:

Compare your initial labeling of your unknown samples with what you determined them to be as a result of the analysis scheme. Can something such as flexibility or hardness be used to identify the kind of plastic? Were the unknown samples as easy to identify as the resin pellets? What was the percentage of correct classifications before you tested the unknown samples? What factors contributed to this percentage?

Questions:

Use the Density Table at the end of this lab to help with the answers to these questions:

1. Your boat is sinking about two miles off shore and you are not a good swimmer. You notice six large solid plastic blocks labeled 1, 2, 3, 4, 5, 6. Which two should you grab and why?

2. You wish to make a plastic handle for a cooking pan out of recycled plastic. Which plastic should you avoid?

3. You decide to jazz up your bathroom cabinet by transferring the fingernail polish remover into a more stylish container. The next day you open the cabinet door to find a messy blob. What was the plastic used in this stylish bottle? What is the active ingredient in the fingernail polish?

4. From what you observed, tell the approximate density of the isopropyl alcohol solution and explain.

5. Why is it important to dislodge any adhering bubbles in the density tests?

6. Sometimes plastic containers are made from two polymers and not just one. What would happen to the water density test if LDPE and PP were mixed? If Pet and HDPE were mixed?

Notice the test areas on the different lab benches. Some tests are to be done only at those locations, while others will be performed at your tables. There are three specific test areas in the room that are set up: acetone test, heat test, oil test.

Follow the directions on the attached sheet for each test using the analysis scheme below.

Density Table

Substance	Density
water	1.00
(#1) PET	1.38-1.39
(#2) HDPE	0.95-0.97
(#3) PVC	1.16-1.35
(#4) LDPE	0.92-0.94
(#5) PP	0.90-0.91
(#6) PS	1.05-1.07