Cross-Linked Glue

Introduction: When a saturated borax solution is added to a glue-water mixture, the viscosity increases several orders of magnitude. The resulting “gluep” is either a bounce-able liquid or a slow-pouring solid (or both).

Purpose: To produce gluep on which to perform a variety of experiments.

Materials: wood glue food colouring sodium borate (Borax) solution distilled water 100 mL beaker plastic bag stirring rod electronic balance

Procedure: 1. Place a 100 mL beaker on the balance. Zero the balance to read zero. 2. Weigh 20 g (or measure 20 mL) of wood glue into the beaker. 3. Add 2-3 drops of food colouring of your choice. The total number of drops must not exceed 3! 4. Stir in the colouring until the colour is uniform. 5. Add 20 mL of distilled water to the coloured glue. 6. Add 20 mL of the Borax solution to the glue and water. 7. Stir the solution until a lump forms on the end of the stirring rod. 8. At this point, use your fingers to remove the lump from the end of the rod. Place it back into the remaining solution in the beaker, and mash the solution into the lump with your fingers. 9. When the lump begins to feel rubbery, remove it from the solution. 10. Rinse it and your fingers under the tap. 11. Store your “gluep” in a sealed plastic bag. 12. Wash your hands with soap and water.

Observations: 1. Press and shape your “gluep” into a ball. Drop it. What happens? 2. Place the ball on your desk and leave it for a few minutes. What happens? 3. Slowly try to stretch your “gluep”. Does it stretch? 4. Twist it quickly. Does it tear? 5. Can your gluep be inflated?

Discussion: 1. Design an experimental procedure to determine resilience (ability to bounce), rest and relaxation, stretchability, and inflatability. Record your observations for each experiment. Have two other lab groups perform your experimental procedures. Record their results and compare with your own. 2. In what ways is your gluep similar to the gluep in other groups? In what ways does it differ?

Conclusion