Polystyrene Bead Molding

On September 7th and 14th of 2000 my lab partners and I conducted the polystyrene bead molding project. My lab partners are Josh Dick, Mike Ward, and Keith Matlock, and we conducted the procedure in room W126 of the Kansas Technology Center. We were to attempt to make polystyrene bead molds using two different methods. In theory we would be able to perform the bead molding.

Polystyrene bead molding can be performed in two ways. One way is to fill the mold 25 to 30 percent full and then applying heat, either boiling water or baking it. Another way is to boil the raw beads, dry the beads, fill the mold with them, and then heat it in an oven. We were to attempt both of these procedures in our lab project. My expectations were that the molds would turn out good.

Materials & Equipment Locations
water container to boil water lab
electric stove lab
oven lab
aluminum molds lab
pan container to dry expanded beads lab
polystyrene beads refrigerator in lab
sieve lab

raw bead expansion procedure
1. First we turned on the electric stove and placed the water container that was about two thirds full on the stove so the water could boil.
2. Then we filled the molds about 25 to 30 percent full and closed the molds with the mold nuts.
3. When the water began to boil we placed the molds in the boiling water.
4. We left the molds in for about twenty minutes and then pulled them out and ran cold water over them in the sink for about a minute.
5. We removed the mold nuts and took out the molded materials.
pre-expanded bead procedure
1. First we put the raw beads in the boiling water and let them expand.
2. Then we removed them from the water with a sieve.
3. We placed the expanded beads in a pan container so they could dry. They were left to dry for a week, until our next lab meeting.
4. After the beads had dried we filled a mold with them and placed the mold in the Blue M Oven, which was preheated to 275 degrees Fahrenheit.
5. The mold was left in the oven for twenty minutes and then removed.
6. After cooling the mold we removed the mold nuts and removed the molded materials.

The raw bead expansion procedure was successful; the beads expanded and made terrific molds. While being heated in the mold the expansion of gasses caused the beads to expand. Our molds were in the shapes of spheres, one looked like a softball and the other looked like a regular sphere. Below are hand sketches our molds.

The outcome of the pre-expanded bead mold was less fortunate. The beads did not take shape of the mold. To be more precise the beads did not change at all.

In conclusion the raw bead expansion procedure appears to be a better method for polystyrene molding. The raw bead expansion procedure proved true to my expectations and the molds turned out good. However we apparently performed the pre-expanded bead mold incorrectly and the results were a failure. After performing the lab I looked through the job sheet for this project and found a side note we overlooked on page 34. It specifically states to use freshly pre-expanded beads and the storage of expanded beads is 6 days maximum.