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PVA and Sodium Borate Crosslinks

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A 5 to 1 ratio of PVA and sodium borate creates crosslinks with the polymer to produce a ball-like solid without compromising the desired ability to bounce, stretch and maintain shape through extreme temperature.

Introduction:
Polyvinyl alcohol is a polymer that when combined with sodium borate creates covalent crosslinking bonds between the polymers, which change the solution from a liquid into a jelly-like solid that can be formed into a ball. 2 A polymer is a chain made of units combined in the same linkage throughout the entire substance. 2 Polymers are used extensively in today’s world to create paper, bike tires, plastic, PVC and many other household common items. 3 The bonds in the polymer are cross-linked; therefore the ball should be flexible and have the ability to stretch considerably. 2 Due to the fact that the sodium borate is the solution that causes hydrogen bonds, which do not hold the ball together, we can assume that the greater amounts of sodium borate will cause the ball to have undesired properties and fall apart.⁵

By keeping the amount of borax used constant and changing the amount of PVA the experiment should show which ratio is better suited for the goal of creating a ball. The ball needed to be able to bounce, not fall apart, be flexible but come back to its original shape after stretching, be nontoxic, odorless, and easy to make in order to lower manufacturing costs. After finding the top two ratios they will be tested in cold and hot conditions that are similar to the areas in which the balls will be shipped. The ice bath represents Alaska and the hot bath represents New Mexico. The following picture shows the crosslinking between the PVA and sodium borate. The borate ion has bonded with the hydroxyl (OH) groups of the polymer and links them together. ¹ The molecular formula of PVA is [-CH2CHOH-]n and the chemical structure of sodium borate is Na2B4O7.

Diagram
Borate ions crosslinking with the PVA chains.

While performing the experiment safety goggles should be worn at all times and gloves should be worn at all times while pouring the solutions and handling the gel. Do not taste the gel or get it on your clothes because it can stain. ¹ Procedure for Experiment 1:

1. In three separate 10 mL graduated cylinders measure out 10 mL PVA, 8 mL PVA and 6 mL PVA. 2. In three separate 10 mL graduated cylinders measure out 2 mL sodium borate, 2 mL sodium borate and 2 mL sodium borate. 3. In one 250 mL beaker combine 10 mL PVA and 2 mL sodium borate. 4. For a minute hold the beaker and swirl it so the contents can combine. Put to the side. 5. In a 250 mL beaker combine 8 mL PVA and 2 mL sodium borate. 6. For a minute hold the beaker and swirl it so the contents can combine. Put to the side. 7. In a 250 mL beaker combine 6 mL PVA and 2 mL sodium borate. 8. For a minute hold the beaker and swirl it so the contents can combine. Put to the side. 9. Taking the first beaker that is holding the 10 mL PVA and 2 mL sodium borate scoop out the contents with your hand and for 20 seconds roll your hands together to form a ball with the gel. 10. Test its bounce ability by dropping it on the table and using a ruler measuring how high it bounced. Record. 11. Test its ability to stretch by holding it between two fingers and dangling above the table. Use a ruler to record how long it stretches before breaking. Record. 12. Repeat steps 9-11 with the other two beakers and their contents. After seeing the result we decided to try one more ratio that had the lowest amount of sodium borate. 1. In a graduated cylinder measure out 6 mL PVA.

2. in a graduated cylinder measure out 1 mL sodium borate.
3. In a 250 mL beaker combine the 6 mL PVA with the 1 mL sodium borate. 4. For a minute hold the beaker and swirl it so the contents can combine. 5. Scoop out the contents by hand and for 20 seconds roll your hands together to form a ball with the gel. 6. Test its bounce ability and stretch ability like the previous experiment. Record. Procedure for Experiment 2:

Making the Balls:
1. Measure out 6 mL of PVA into a graduated cylinder, measure out 10 mL PVA into another graduated cylinder. 2. Measure out 2 mL of sodium borate into a graduated cylinder, measure out 1 mL sodium borate into another graduated cylinder. 3. In one 250 mL beaker pour the 6 mL PVA then add the 1 mL sodium borate. 4. For a minute hold the beaker and swirl it so the contents can combine. Put to the side. 5. In one 250 mL beaker pour the 10 mL PVA and then add the 2 mL sodium borate. 6. For a minute hold the beaker and swirl it so the contents can combine. Put to the side. 7. Repeat steps 1-6. This will result in two balls of the 6 mL PVA and 1 mL sodium borate and two balls of the 10 mL PVA and 2 mL sodium borate. Ice Bath:

1. While the contents are resting set up an ice bath, in a 400 mL beaker fill middle with ice and then add water to the top marking. 2. Set up a thermometer stand and stick the end of the thermometer into the ice water. 3. The water should be at 1°C, Keep watch of the thermometer readings and add ice to keep it at a steady temperature. 4. Using the beaker with the solution of 10 mL PVA and 2 mL borax, scoop out the contents with your hands and for 30 seconds roll it into a ball. 5. Once the ball is formed place it into the ice bath that should be at 1°C. 6. Let sit for 2 minutes and record any changes you observe. 7. With your hands pull the ball out of the ice bath. Record any changes in the way it feels. 8. Test its bouncing ability by dropping it a foot high above the table and using to ruler to measure the height it bounced, record observations. 9. Hold the ball in one hand and see how far it stretches using a ruler when allowed to dangle. Record. 10. Repeats steps 1-6 using the solution of 6 mL PVA and 1 mL borax. Heat Plate:

1. While your contents are resting set up a hot bath, in a 400 mL beaker fill to the top marking with water. 2. Place beaker on a hot plate and set to a setting of four. 3. Set up a thermometer stand and stick the end of the thermometer into the water. 4. The water should be at 35°C, adjust the heat setting as the experiment continues in order to keep it at a steady temperature. 5. Using the second beaker with the solution of 10 mL PVA and 2 mL borax, scoop out the contents with your hands and for 30 seconds roll it into a ball. 6. Once the ball is formed place it into the hot bath that should be at 35°C. 7. Let sit for 2 minutes and record any changes you observe. 8. With your hands and a stick if needed pull the ball out of the ice back. Record any changes. 9. Test its bouncing ability by dropping it from a foot above the table and using a ruler to measure the height it bounces, record observations. 10. Hold the ball in one hand and see how far it stretches using a ruler when allowed to dangle. Record. 11. Repeat steps 1-6 using the solution of 6 mL PVA and 1 mL borax. 10 Minute Cold Water Experiment:

1. Fill two 400 mL beakers halfway with ice, then to the top line with water. 2. Set up two thermometers, put one thermometer into each beaker. 3. The temperature should be at 1°C, add more ice as needed throughout the experiment so the temperature is steady. 4. Take both the 10 mL PVA: 2 mL Borax ball and the 6 mL PVA: 1 mL Borax ball from the previous cold water experiment and put them into their separate beakers. (Make sure to take note which ball goes into which beaker) 5. Let sit for 10 minutes recording any changes, make sure temperature is constant. 6. Remove both balls from the water with hands.

7. Perform the bounce test on each, record.
8. Perform the stretch test on each, record.
Data:
Experiment 1:Finding the Best Ratio
Solution| Color/Texture| Bounce Test| Stretch Test| Other Observations| 10 mL PVA2 mL borax| Clear/cold to touch and gelatinous | Bounced 2 inches| 14 inches| In the beaker formed a gel but with liquid left over surrounding it. Went back into its ball shape after being stretched. Didn’t stick to hands or table.| 8 mL PVA2 mL borax| Clear/cold to touch and gelatinous| Bounced 1 inch| 7-1/2 inches| In the beaker formed a gel but with liquid left over, had less liquid than the 10 PVA: 2 Borax solution. Fell apart after being stretched.| 6 mL PVA2 mL borax| Clear/cold to touch and gelatinous| Did not bounce| 2 inches| Formed into a jelly with no liquid left over, stuck to bottom of container and doesn’t move around. Stretched 2 inches and stuck to gloves.| 6 mL PVA1 mL borax| Clear with slight white coloring/cold to touch and gelatinous| Bounced 2 inches| 11 inches (but stretched very slowly)| Formed a gel with very little liquid left over, after stretching it formed back into a ball.

In experiment one we first believed that the ratio of 6:2 (PVA to SB) would be the best because it had no liquid left over which means we wouldn’t be wasting solution. However when forming the ball the solid absorbed the liquid and formed a ball that could be flexible and malleable. From experiment one we concluded the two best ratios were of the 5:1 and 6:1 and were going to be tested for their behavior in extreme temperatures.

Experiment 2:Testing Exposure to Cold (Alaska)
Solution| Time in Ice Bath| Color/Texture| Bounce Test| Stretch Test| Other Observations| 10 mL PVA, 2 mL Borax| 2 minutes| Same color (clear)/slimy| Doesn’t bounce| 15 cm| Slightly breaks when bounced, but immediately comes back together, as it warms up from hands it starts to be able to bounce again. Within a minute of room temperature it is back to normal.| 6 mL PVA,1 mL Borax| 2 minutes| Same color(clear)/slimy| Bounces very slightly, 1 inch| 30 cm| Slightly breaks when bounced (but not as much as 10:2 ball), but immediately comes back together, as it warms up from hands it starts to be able to bounce again. Within a minute of room temperature it is back to normal.

By testing for cold for two minutes we saw how each ball would react when in the cold for a short period of time, such as if a kid was walking from the car into the house. Both were satisfactory and able to come back to its original shape and properties. Testing Exposure to Heat (New Mexico)

Solution| Time in Hot Bath| Color/Texture| Bounce Test| Stretch Test| Other Observations| 10 mL PVA, 2 mL Borax| 2 minutes| Same color (clear)/very slimy, gooey| Cannot complete bounce test| Cannot complete stretch test| Turned to goo almost immediately, sinks to bottom into an oval shape, cannot be pulled out because it just falls apart into the water| 6 mL PVA,1 mL Borax| 2 minutes| Same color (clear)/very slimy, gooey| Cannot complete bounce test| Cannot complete stretch test| Turned to goo almost immediately, sinks to bottom into an oval shape, cannot be pulled out because it just falls apart into the water|

By testing for heat we were able to determine if the balls could handle the temperature of New Mexico where they were being shipped from. From the results we can conclude that neither of the ratios are able to maintain their shape when exposed to higher temperatures.

Testing Prolonged Exposure to Cold
Solution| Time in Ice Bath| Color/Texture| Bounce Test| Stretch Test| Other Observations| 10 mL PVA, 2 mL Borax| 10 minutes| Same color (clear)/slimy| Doesn’t bounce| 32 cm| When bounced it immediately breaks and doesn’t come back together on its own, it can be rolled back into a ball shape for the stretch test. As it warms up it begins to be able to bounce again.| 6 mL PVA,1 mL Borax| 10 minutes| Same color (clear)/slimy| Bounces very slightly, 1 inch| 45 cm| Slightly breaks when bounced (but not as much as 10:2 ball), but immediately comes back together, as it warms up from hands it starts to be able to bounce again. Within a minute of room temperature it is back to normal.|

By keeping the balls in the water for an extended amount of time we were able to see how cold affected their properties. The 6:1 ratio was slightly stronger and maintained and regained its shape faster. Conclusion:

By combining numerous ratios of PVA and borax the most effective combination was of the 6 mL of PVA and 1 mL borax. It not only uses the least amount of each solution which would optimize manufacturing costs but it retains its ability to bounce and stretch when put through extreme cold temperatures. However this product will not work well in hot areas such as New Mexico. The heat from the water caused the viscosity of the product to change; it fell apart in the water and could not be handled, it just slips off of the apparatus being used to pull it out. Once the water is poured out of the beaker and the product was allowed to cool it stuck to the surface it was on and did not go back to its original ball-like shape. Originally the combination of 6 mL PVA and 2 mL borax was believed to be the best combination because it did not have liquid left over in its beaker; however the borax caused the product to lose some of its properties that come from the polymer PVA. It lost its flexibility wouldn’t form into a proper ball. Research:

Polymers, especially polyvinyl alcohol, are extremely useful in today’s world and in medicine. By using the known properties of PVA scientists can anticipate how it will react with other solutions and use these hypothesis’ to develop new products. That is what we did in this lab, knowing sodium borate creates crosslinks with the chains in PVA we were able to design a ball that could maintain its shape but stay malleable. In today’s science PVA is being used to create transdermal patches, encapsulation of systems that deliver drugs and in dressing of wounds.

Citing:

1Nuffield Foundation. http://www.nuffieldfoundation.org/practical-chemistry/pva-polymer-slime 2RSC: Advancing the Chemical Sciences. http://www.rsc.org/Education/EiC/issues/2005_Jan/exhibition.asp 3Materials Science. http://dsc.discovery.com/tv-shows/curiosity/topics/polymer-based-products-you-use-every-day.htm ⁴Basque Research. http://www.basqueresearch.com/berria_irakurri.asp?Berri_Kod=3894&hizk=I ⁵Slime & Superballs. http://icn2.umeche.maine.edu/newnav/Homepage/Highschool/Slime/lecpolymers2.htm 6Science of Slime. http://www.ccmr.cornell.edu/education/modules/documents/ScienceofSlime_student.pdf

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