SCH4C             Lab #9 - Making Glyptal Resin Plastic

Introduction:  Phthalic anhydride and Phthalic acid can be used along with glycerol to create a plastic.  They are combined and heated in a test tube.  A clear plastic that is formed is poured into an aluminum or plastic cap from a plastic soda bottle.  A penny is placed in the cap and permanently embedded in the plastic.

Materials:  Phthalic acid, glycerol, sodium acetate, old large test tube, plastic bottle cap.

Safety Note:  Students should wear goggles and plastic disposable gloves. Avoid breathing the vapours and avoid skin contact with the phthalic acid..

Procedure:
 
1.    Place 10 grams of Phthalic acid in a large test tube.  Use an old test tube because it be discarded at the end of the experiment.  
2. Add 0.5 grams of sodium acetate to the test tube.
3. Add 4.0 mL of glycerol.
4. Heat the test tube slowly to dissolve any remaining solids.
5. Continue heating until the mixture boils for about 5 minutes.
6. Prepare a mold by cleaning and drying the plastic bottle cap. (the 3 L size works best)
7. Pour about half of the hot liquid into the plastic cap.
8. Carefully place a penny (or other object that you want to preserve) in the liquid in the cap and then add the remaining liquid on top of the penny.
9. Let the plastic cool for about 10 minutes at room temperature.  then place it on top of a container of crushed ice for further cooling.
10. Using pliers, strip away the plastic cap to free the plastic with its embedded penny.

Reaction:  this is essentially an esterification reaction between the glycerol and phthalic anhydride. Water is produced during esterification and is removed by boiling the mixture.  this plastic, glyptal resin, is a thermosetting plastic formed by phthalic anhydride acting as a cross-linker to strands of glycerol molecules together in a  polymer.
                 Glycerol Phthalic acid
Questions:
1.    When the reaction appears to boil, what substance is actually boiling off?

2.    How does the structure of the phthalic acid molecule change in the esterification reaction?

3.    How does the structure of glycerol change?