Cross-Linking Elmer’s Glue with Sodium Borate or "The Slime Lab"

Background: the mixture of Elmer’s glue and borax, a putty or slime is produced. The atomic structure is:

Here is the vocabulary used:

• polymer: A polymer is like spaghetti. It is a long string or chain of molecules that is slippery, rubery, and bouncy. The spaghetti flows at first when it is wet. Then when it starts to dry, it sticks to itself. When it is all of the way dry, it is like a solid. An example of a polymer is the little marble like orbs that are marketed as “orbeez.” They are bouncy and they are actually super absorbent polymers. They refract light the same way water does, so they “disappear” in water.
• 
• liquid polymer: This means that the polymers can slide past each other without catching. They flow.
• elastomer: It is a rubbery solid in which the polymer’s molecules catch on each other.
• Borax: The borax compound makes the glue molecules turn into an elastomer. It is the cross-linking agent.
• polyvinyl alcohol (PVA): this is the secret ingredient that makes slime longer lasting and more transparent.

Materials:

• 105 mL of water
• 25 mL of Elmer’s Glue
• 1 tsp. Borax
• A tsp or plastic spoon
• 1 graduated cylinder
• 600 mL beaker
• 250 mL beaker
• stirring rod

What we did: We put 100 mL of water and a heaping tsp. of borax into the 600 mL beaker. We stirred the mixture for a long time with a plastic spoon trying to dissolve the powder, but it didn’t dissolve very much. Then we put 25 mL of elmers glue into the 250 mL beaker and added 5 mL of water. We stirred that mixture with the stirring rod. Next, we poured 40 mL of the borax mixture into the glue solution and stirred. We dumped the remaining liquid out and then played with the slime. We added various measures of different ingredients.

Observations:

This is the polymer after I had played with it for a few minutes. It lost its moisture and broke into pieces. I tried to squish them together, but they wouldn’t attach. The long strings of molecules were then elastomers, and they would not go back without the help of water.

This was from experimenting on our own. We put straight Elmer’s glue into the beaker with some leftover borax solution and a skin was created. It was almost like a sack, but it couldn’t be popped. We had to pull it apart to see the glue inside.

This is the glue sack from above being pulled open. There is a lot of straight glue inside the sack and you can see that we had to pull it apart. That is why water needs to be added to the glue before the borax and water are poured in. It straight glue was poured into the borax, it would just form a skin on the outside and all of the glue wouldn’t be able to come in contact with the borax.

This is the polymer at first. This was right once we started to mix the borax and glue solutions. The reaction was almost instantaneous! It clumped into one big slime blob and left a bunch of borax water behind.

This is half of the total amount of polymer that I rolled into a ball. It was pretty bouncy but it was hard to make a perfect circle, so it bounced in all different directions. You can see the 600 mL beaker in the background. The white stuff on the sides is the leftover borax that didn’t dissolve when we stirred it.

Relation: This polymer and the “Orbeez” are similar because they are not only bouncy, but they are both easily breakable. You can crush or pull these polymers apart. They both contain a lot of water and they are both a lot of fun to play with!

Questions:

1. The slime is not very visco-elastic because it breaks pretty easily. It stretched about 6 inches and then it broke in half

2. The physical properties of the Elmer’s glue that changed after the borax was added were its flowing ability, it was soft instead of slimy, it was no longer sticky, it turned bouncy, and it was more condense.

3. If more borax was added, the slime would be more concentrated, less stretchy, and grainy.

4. Water affected the polymer by making it more slimy and less concentrated. It made the polymer more stretchy and more sticky. It had moderate elasticity.

5. I circled the repeating molecule:


6. This is the structure of polyvinyl alcohol:

7. I circled the borax cross linking agent: