Key Concepts
Wetting, Van der Waal’s forces, adhesion

Introduction

You may have heard of the space shuttle Apollo 13, or seen the movie about the amazing survival of the ship’s crew after an explosion aboard the ship. What you may not know, is that duct tape helped save the lives of the Apollo 13 crew! NASA had to figure out a way to keep the 3 crew members alive in a tiny lunar module that was only meant to hold 2 people for 36 hours. They instructed the crew to build life-saving air filters using cardboard, plastic bags, space suit parts and – you guessed it – duct tape! The same tape that you use in projects around the house was also used to save lives on a space ship!

In this activity we’re going to explore how duct tape works – and what can make it stop working.

This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Background

You probably use tape all the time, but have you ever wondered how it works? Why doesn’t it feel wet, like glue? What makes some tape stronger or weaker?  For this activity, we need to understand how tape works!

Household glues like Elmer’s and super glues are liquid when you apply them, then they go through a chemical change and harden to glue things together. Tape works completely differently – there are no chemical reactions! The stickiness of duct tape (and most other strong household tapes) are in large part the result of 2 physical properties, known as wetting and Van der Waal’s forces.

Wetting is a word that we use to describe how effectively an adhesive can penetrate (or sink into) the material it is applied to. Imagine a drop of water on a paper towel, and a drop of water on a piece of wax paper. Water dropped on the towel will sink into, and penetrate, the paper towel. Water dropped on the wax paper will form a water droplet, and will not penetrate the wax paper. Materials that are good at wetting can penetrate into the pores of the materials they’re applied to, much like the water into the paper towel.

Believe it or not, the adhesive on your duct tape is good at wetting. When you push a piece of tape down onto a piece of paper, you help the molecules on the sticky side of the tape penetrate into the surface of the paper.

Once the adhesive molecules have penetrated the surface of the paper (or other surface!), Van der Waal’s forces come into play. These are weak attractions between molecules that normally might not be attracted to each other. Because of the careful arrangement of these molecules in the tape, the tape molecules are able to form physical bonds with the paper molecules. The tape molecules also cohere (stick to each other), and as a result, tape can hold together and stick to, a huge variety of important items!

Materials

  • 1 roll of Duct Tape (or other brand of heavy duty sticky tape)
  • 1/2 cup of water
  • A freezer
  • A glass dish
  • ~1 foot of wax paper
  • A ruler or measuring tape
  • Scissors
  • 1 small sandwich bag
  • 2 large paper clips
  • 10 Nickels (if unavailable, substitute other coin denomination so long as it is 10 of the same coin)
  • A small baking tray or plate (at least 12 inches across)
  • A timer or clock
  • Paper
  • A pen or pencil
  • A partner
  • A spoon

Preparation

  1. Cut one 12 inch piece of tape. Carefully place this piece sticky side UP on your tray or plate. Put this tray in the freezer. Set your timer for at least 25 minutes (or note the time on your clock).
  2. Use a paper clip to poke a hole through a top corner of your sandwich bag. Make your hole at least 1 inch from the edge of the bag. Loop your paperclip through the hole (you may have to bend it slightly), so that the bag hangs from the paperclip.
  3. On your paper, make a table like the one below:

Duct Tape Treatment/

Condition

# of Nickels

Length of hanging tape

Stickiness of Tape

Glass Pan

 

 

 

Wax Paper

 

 

 

Wet

 

 

 

Frozen

 

 

 

Procedure

  1. Use your scissors to cut one, 12 inch strip of tape.
  2. Gently attach the end of this tape to a table or counter top, allowing it to hang free without touching anything. This is your tape control, you will use this to compare the stickiness of the other tape you will use in this activity.
  3. Use your scissors to cut another 12 inch strip of tape.
  4. Attach 6 inches of the tape to the bottom of your glass pan. Press it down firmly using your hand, or a credit card if available. Allow the other 6 inches to hang below the dish (like a tail!)
  5. Have your partner hold the dish so that the tape can hang free.
  6. Use your scissors or the extra paper clip to poke a small hole through the hanging end of the tape (approximately 1 inch from the end) of the tape.
  7. Insert your paperclip through the hole, so that both paperclip and bag hang from the end of the tape.
  8. While your partner holds the glass dish steady, slowly add nickels to the bag, pausing to observe any changes after adding each coin. What happens to the tape as you add nickels? Do you see any changes?
  9. If the tape pulls off the glass dish before you run out of nickels, record the number of nickels that the tape held in the first column of the Control row in your table. If you are able to put all 15 nickels in the bag, record the number 15.
  10. Use your ruler to measure the tape hanging from the dish. Note the length of tape in the ‘Length of Tape’ column for the Control role in your table. Notice whether the length of the tape has changed since you started. Did the weight of the coins pull more of the tape free, making the tail longer?
  11. Gently pull the tape off the glass plate. As you pull the tape, feel the sticky side. Compare this to the hanging half of the tape, that never touched the pan. Does one half feel more or less sticky than the other? Does it look different?
  12. Compare the stickiness of the used tape to the tape hanging from the table. Does it feel more or less sticky?
  13. Rate the stickiness of the used tape on a scale of 1-10. Use your control tape as a comparison. If that is a 10, how sticky is the used a tape?
  14. Dispose of your used tape.
  15. Use your scissors to cut another 12 inch strip of tape.
  16. Repeat steps 4-14, but this time attach the tape to your Wax paper. When your partner holds the Wax paper, have them brace it against a book or your glass pan, so that it doesn’t sag with the weight of the coins.
  17. When you get to step 11, if the tape doesn’t come off the paper as you pull it, you can write ‘could not remove’ in the ‘Stickiness of Tape’ Column.
  18. After you have recorded your results in each column of the Wax Paper row, dispose of your used tape.
  19. Use your scissors to cut another 12 inch strip of tape.
  20. Before attaching the tape, carefully place it sticky side up on a counter or table top. Place your ruler next to the tape.
  21. Use your spoon to drop several spoonfuls of water onto half the length of the tape. Make sure that half of the tape is thoroughly wet.
  22. Repeat steps 4-14, attaching the wet half of the tape to your glass pan. If the tape doesn’t stick, write ‘0’ in the nickels column, and ‘Did not stick’ in the ‘Length of Tape’ column.
  23. Compare the stickiness of the wet half of your tape to the control tape. Rate the stickiness of the wet tape on a scale of 1-10 in the ‘Stickiness of Tape’ column, in the ‘Wet’ row. Does the wet tape feel different? In what way? Does it look different? How would you explain the differences you observe?
  24. After you have recorded your results in each column of the Wet row, dispose of your used tape.
  25. Remove the plate with your tape on it from the freezer (as long it has been at least 25 minutes!)
  26. Repeat steps 4-14 attaching the frozen tape to the glass pan. If the tape doesn’t stick, follow the directions in step 22.
  27. Review your table. In which condition was the tape able to hold the highest number of nickels? The lowest? Which condition had the highest rating for tape stickiness? Which condition had the lowest?

Extra: Repeat the activity, sticking the tape to a non-stick pan. Be sure to ask for permission first! Add a row to your table to record the results!

Extra: Experiment with other types of tape. Are some more sensitive to water, or temperature than others? Do some hold better than others?

Tip: You can remove any residue left by the tape using olive oil, or an olive oil soaked paper towel. Allow the olive oil to saturate the residue for at least 15 minutes, then scrub it off using a sponge.

Observations and Results

During this activity, you should have found that the stickiness of your tape depended on two general factors; 1. The condition of the tape, and 2. The surface where you were attaching the tape. While the tape stuck firmly to the glass pan, when the tape was wet or frozen it was significantly less sticky compared to your control tape. In addition, when the you stuck the tape to wax paper, it did not stick as well as it did to the glass pan.

So let’s start with the conditions of the tape itself, why doesn’t tape work when it’s wet? Tape loses its stickiness when the adhesive molecules in the tape become wet. When this happens, the water acts as a barrier to wetting (so the adhesive molecules can’t sink into the glass pan) and also prevents the physical bonds from forming between the tape and the pan. The water acts like a wall between the tape and the pan, they can’t get together!

Freezing the tape also decreased it’s adhesive wetting capacity. Again, imagine a few drops of liquid water dropped onto a paper towel, compared to an ice cube dropped onto a paper towel. The liquid water will penetrate the paper towel much more quickly and effectively than the ice cube. Similarly, the adhesive molecules in the tape, when frozen, cannot penetrate the other surfaces as well, so the tape can’t get a firm ‘grip’ on the things you want it to stick to.

In the case of wax paper, the tape didn’t stick as well as it did to the glass pan, but this time it was because of the wax paper. Go back and think about the water drop on the paper towel, compared to the wax paper. Just like the water drop can’t penetrate the wax paper, neither can the tape! Wax paper blocks most materials from wetting, which makes it great at repelling water, food, and in this case, tape!

More to Explore

Credits

Megan Arnett, PhD, Science Buddies

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Key Concepts
Wetting, Van der Waal’s forces, adhesion
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