When water, white glue, and borax are mixed together, a reaction occurs where the OH^- groups in the glue are crosslinked and a rubber-like product is produced. The B(OH)₄^- ion is believed to crosslink the polymer chains through hydrogen bonding as shown below.

Poly(vinyl acetate) chains crosslinked by the B(OH)₄^– ion.

The Problem

The toy company that has just hired you lost the recipe for their famous Glüg (a popular toy item). Your team's job is to determine the appropriate amount of borax, glue, and water to make a sample of Glüg that meets the following criteria:

1. It should be tacky, but not sticky, grainy, or runny.

2. It should not have any excess water after mixing (this will be observed immediately)

3. It should stretch easily when stretched slowly.

4. It must have a shelf life of at least 24 hours (this is a minimum).

The company has given you a small laboratory to conduct your experiments. You will have one class period in which to prepare all of your samples. The samples will be tested on a later date (at least one day later). Below is a list of materials you will be allowed to use.

Devise a plan of your tactics and methods for determining the best amount of borax. Decide how much borax, glue, and water you will use in each of your different samples. Once a plan has been devised, take it to your teacher and have it approved. You need to make as many samples as possible to have a variety from which to choose.

Materials and Apparatus

Day 1

White glue
Powdered borax
Balance
Zip lock plastic bags (for storage)
Baby food jar (or a jar with a lid)
Marker to label bags
10 ml graduated cylinder
50 m l graduated cylinder
Spatula or Popsicle stick
50 ml beaker (to use for mixing the borax and water)
Water

Day 2

Glüg samples from Day 1
5 feet of aluminum foil (to stretch the samples on)

Pre-Lab

What is the plan to approach this problem? Write a description of your procedure as if you were addressing the board of directors at the toy company. Be sure to explain the number of samples your group will prepare and the amounts of glue, water, and borax in each. You need to back up your methodology with reasons why you chose your strategy. Also, think of ways you might need to test the criteria of each sample. Remember that the board of directors knows little about chemistry, so you must explain thoroughly. This plan must be approved by the teacher before proceeding with the experiment.

Safety

Wear goggles throughout the experiment. Be sure to wash your hands thoroughly at the end of the laboratory experiment. This lab can be messy if proper precautions are not met. Keep the Glüg in a sealed zip lock bag, and keep it off clothes and carpet.

General Safety Guidelines

Data and Analysis

1. Create a table to organize all your experimental data. Be sure to include results to describe the criteria of the Glüg.

2. Which sample had the best shelf life? (Which sample maintained its properties the best?)

3. Which sample stretched the farthest without breaking or being overly messy?

4. Which sample had the best texture (tacky not sticky, runny, or grainy)?

5. Write a report for the board of directors to describe which sample of Glüg met the criteria best. This report should describe in detail the properties of the final product as well as your methods for determining the final results. Also, discuss how well your plan worked and any changes you had to make. You must also include a plan to make the product reproducible. The factory will need to make your product; do you think this is possible?

The Crosslinking Page — learn more about crosslinking and crosslinked polymers on this page, part of The Macrogalleria from the University of Southern Mississippi.

This activity was created by Stacy Brust.