Experiment 4

Don't Throw it in the Garbage

Investigating the Classification and Processing of Recycled Products

Objective: The objective of this desk-top laboratory procedure is to increase awareness of recycling polymers through the use of the "three arrow numbering system". Classes of polymers, uses, and physical properties of some thermoplastics will be investigated.

Review of Scientific Principles:

Thermosetting plastics are types of polymers that will characteristically decompose before they will melt. Thermoplastics are polymers are remoldable when heated. These thermoplastics are the ones that we like to recycle. Refer to the "Scientific Principles Section" of this module to obtain a more complete discussion and explanation as to why these two classes of polymers act as they do.

Time: Around 40-45 minutes are required for this experiment and the demonstration at the completion of the experiment.

Materials and Supplies:

Bring two (2) different polymers to class. If these are containers or wrapping material, make sure they are clean and empty. The polymers are identified by the 3-arrow number system placed somewhere on the container. Identify the type of polymer and its use before class.

Procedure:

1. Answer question #1 below concerning your own polymer.
2. As the collection box is passed around, identify orally to the class the type of polymer you acquired, its number, and its use.
3. Place your polymer into the box for a future experiment. The excess will be recycled.

Data and Analysis:

1. What are the recycling numbers, names, and uses of the two polymers which you brought in?

   Number	Name	Uses

   
   
2. What are the recycling numbers, names, and uses of four (4) different polymers which other students contributed?

   Number	Name	Uses	Student Names

   Questions:

3. Your plastics (polymers) will melt or soften at the following temperatures:
   HDPE: about 130^oC
   LDPE: about 110^oC
   PET: 250 to 260^oC
   PP: 160 to 170^oC
   PS: (in solid or foam forms) 70 to 115^oC
   PVC: 75 to 90^oC

   Identify each of the polymers that you have listed above (in questions #1 and #2) and note its melting point.

   Which of the polymers would melt in the liquids held at the temperature that has been listed below?
   a) Which would melt in boiling water (100^oC)?
   b) Which would melt in boiling antifreeze (ethylene glycol) (190^oC)?
   c) Which would melt in glycerin held at 290^oC? Danger: Glycerin would begin decomposing before you reached this boiling temperature.

4. What properties should a polymer possess to be used in each case on the list below? Name two properties for each usage.
   Bag
   Ice cream container
   Water and Snow skis
   Basketball
   Tire

Post Lab Demonstration 4

What Happened to the Polymer?

Procedure:

1. Place a Styrofoam cup inside a 400 ml beaker.
2. Place 20 ml of acetone (this is flammable-keep from flames) into the cup which is inside the beaker.
3. Use a glass stirring rod and stir.
4. Record your observations below.
5. Remove the mass from the beaker using the stirring rod and blot dry with a paper towel. Caution: Acetone will remove paint from surfaces.
6. Make your observations of the mass blotted dry on the paper towel.
7. Dispose of the excess acetone in the sink mixing it with water from the faucet.

Video Clip

Data and Analysis:

Observation of mass in the beaker.

Observation of the mass after it has been blotted dry on the paper towel.

Questions:

Teacher Notes:

Objective: The objective of this experiment is to allow students to identify polymers using the recycling codes, state uses of the polymers, and use melting points in a hypothetical experiment as a means of comparing physical properties of polymers.

Review of Scientific Principles:

Students will be bringing in samples of polymers and identifying them using the recycling codes. The code/name/abbreviation are all listed on the chart at the end of the RECYCLING section of the scientific principles portion of this module.

The code number is found in the 3 bent arrow recycling symbol on the polymer.

One of the main public concerns in America now is dealing with waste. Read the section of this module dealing with recycling techniques, products, and economics.

We will begin a two lab series investigating the physical properties of polymers. Note that the question dealing with the heating of the liquids is strictly hypothetical. This is not to be performed as there is danger with ethylene glycol vapors and with the glycerin decomposing much before the temperatures stated in the question.

Time: This lab is expected to take 60 minutes.

Materials and Supplies:

• a large box to contain samples of polymers
• Styrofoam cup
• 250 ml beaker
• 30 ml acetone
• students supply polymers

Procedure:

1. As a prelab exercise, students are to bring two samples of polymers from home. The polymers should be clean and empty.
2. Students are to answer question #1 before coming to class.
3. Students are to hold up and orally identify the polymer's name, use, and recycling number.
4. Students should place the polymer in the large recycling box after the polymer has been identified.
5. As students orally respond around the room, they can answer question #2.
6. When students are finished responding, students should answer question #3. These are hypothetical questions and are NOT to be performed as a lab.

   Demonstration:

7. A Styrofoam cup is placed into a 250 ml beaker and 30 ml of acetone are poured into the cup. The cup will collapse upon itself. Note that the acetone will remove paint from surfaces.
8. Stir with a stirring rod until the whole cup has collapsed.
9. Use the stirring rod to remove the clump of polystyrene and place it onto a paper towel.
10. Blot the polystyrene dry.
11. The acetone is to be poured down the sink flushing it with copious quantities of water.
12. The clump of polystyrene can be disposed of in the trash can after the experiment.
13. Students are to answer the observations and answer the question as you perform this experiment.

Suggestions:

• The experiment with boiling liquids is hypothetical and not meant to be performed. There are problems with ethylene glycol vapor and glycerin decomposing.
• This is an excellent lab to do before the investigation of "physical properties of polymers."

• After the collection of the polymers, the samples collected can be used for testing in the next laboratory investigation.
• Have a large box available for the collection of the empty containers brought by the student. (e.g., a towel box)
• Have each student identify his polymer, its number and its use.
• After the students identify their polymer, it may be deposited in the box.

Answers to Questions:

1. Student chart.
2. Student chart.
3. Student answer
4. a PVC--Sometimes Polyethylene wrap will be noted to soften in practice.
   b HDPE, LDPE, PP, PS and the one listed above
   c PET and the ones listed above
5. The terms elasticityand strengthcould surely be used for each of the two answers. Discussion of elasticity and strength at different temperatures is appropriate at this point.

Sample Data and Analysis:

Observation of mass in the beaker.

Gooey polystyrene mass.

Observation of the mass after it has been blotted dry on the paper towel.

It is sticky.

1. As an adhesive