Large Test Tube
Chloroform or Toluene
Large Glass Plate
Place 1 gram of a styrofoam
cup which has been broken into small pieces into a large test tube. Add
enough solvent (chloroform or toluene) to prepare a 20% solution (by weight,
use 4 to 5 ml). Stir the mixture until the styrofoam is completely dissolved.
To cast a film, pour the
viscous solution near the edge of a glass plate, spread out and smooth
with a doctor's knife (just one time through), and allow to dry slowly
(usually the film is allowed to dry under a large watch glass). Complete
drying may take several hours (e.g. overnight).
Remove the resultant film
by applying pressure with a spatula or razorblade at the edges of the film.
Mount the film in a cardboard holder and use it as a polystyrene standard
CASTING ON WATER
This method is applicable
to microscale samples and is a very quick and convenient method to evaluate
Polystyrene Sample (e.g.,
foamed polystyrene cup)
diethyl ether solution
Disposable Dropping Pipette
Dissolve about 10 mg of
a polystyrene sample in 1 mL of a 40:60 mixture of dichloromethane: diethyl
ether. Allow the polystyrene to completely dissolve.
Add a small amount of
water to a clean watch glass to make a puddle approximately 5 cm in diameter.
Add the polystyrene solution
dropwise to the top of the water. Observe the surface carefully - a film
will begin to form almost immediately. After several minutes, poke the
film with a stir rod or pipette. If the film is cohesive, gently remove
the film from the surface and place it on a paper towel to dry for ten
This film makes a good
standard for IR spectroscopy. Mount the film in an IR holder or cut a hole
in the center of a business card and mount the film, using tape to hold
it in place, over the hole. Place the holder or business card into the
IR and record the spectrum. NOTE: Additives may have been added to the
polystyrene which will cause additional peaks to appear in the spectrum.
This general technique
also may be used as an interesting demonstration.
Foamed Polystyrene "Peanuts"
There are many interesting
lead-ins and follow-up discussions - be
creative. One example would be a discussion
of waste volume considerations (the collapsed foam certainly occupies much
less space than the original foam!) Young students especially like to try
to solve the problem of how to get a large box full of "peanuts" into a
600 mL beaker. The solution, of course, is to use about 40 mL of acetone.
Place a small amount of
acetone in the bottom of a large beaker.
Add handfuls of polystyrene
The acetone will collapse
the foam (without truly dissolving it).