Organic Chemistry

Silicone Rubber

Purpose: To make a silicone polymer ball

Materials: Sodium silicate (water glass; avoid contact with skin), 95% ethyl alcohol, plastic cup, wooden or glass stirring rods, paper towels, a bowl with water, finger part of disposable glove

Safety: Wear goggles, apron, and gloves. Finished balls will have a pH of 10.

Procedure:

  1. Place 20 mL of sodium silicate solution in a cup.
  2. Slowly add 5 mL of 95% ethyl alcohol while stirring.
  3. Continue stirring with a circular motion until the material polymerizes.
  4. Moisten your gloves with water and roll the polymerized material into a ball. Gently squeeze excess alcohol from the ball and wet it occasionally until its surface glistens. Sometimes the silicone tends to dry out and crumble. If this occurs, moisten your gloves and try to reform the ball as before.
  5. Place the ball inside the finger part of the disposable glove and tie the opening shut.
  6. Try bouncing your ball to see if it is elastic.
  7. Place your ball into the dedicated container on the demonstration cart. Place the stirring rods into the dedicated beaker. Place your cup onto the science cart. Empty the water into the dedicated container, and discard the bowl into the trash.
  8. Wipe down your work area.
  9. Wash your hands before leaving the lab.
Observations:

            As the ethyl alcohol was added to the sodium silicate, the solution started to turn whitish and was thickening.  It turned into a waxy solid.  Immediately, the gloves had to be moistened and the substance had to be molded, otherwise, it would crumble. The substance began forming a sphere and, with consistent moisturizing, became smooth and shiny.  Once it was placed in the finger part of the glove and was dropped, it bounced up again.