Hands-on Activity: Let's Make Silly Putty
Educational Standards :
Pre-Req Knowledge (Return to Contents)
A familiarity with polymeric materials, polymerization and cross-linking. This activity is designed to follow the Everyday Polymers lesson.
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
Each group needs:
To share with the entire class:
Introduction/Motivation (Return to Contents)
Who has played with Silly Putty? The recipe for Silly Putty was created by James Wright of General Electric in an attempt to make a synthetic rubber compound. During World War II, Japan occupied many of the natural rubber manufacturing countries in the Far East and cut off supply to the US. This began to hamper war production efforts, especially the manufacture of tires and boots. Although his invention of was not found to have good practical uses, Silly Putty did find success as a children's toy in 1949!
Today, we are going to follow in James Wright's footsteps and use poly (vinyl alcohol) and sodium tetraborate (borax) solutions to make a slimy polymer, resembling Silly Putty! Did you know that poly (vinyl alcohol), the main ingredient in Elmer's Glue, is a long chain of repeating ethyl alcohol monomers? You can think of these ethyl alcohol monomers -(CH2-CHOH)- as long strands of spaghetti. Sodium tetraborate is an ionic molecule that acts as a linker between the long chains of the polymers (draw Figure 1 on the board). Changing the ratios of polymer and sodium tetraborate solutions in your imitation Silly Putty will affect how it bounces, stretches and goos!
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Students synthesize polymeric materials and create two different formulations of imitation Silly Putty. Then they design new versions of the putty that satisfies one of two different requirement options: very stretchy or rigid enough to bounce well. Students make their different formulations of poly(vinyl alcohol) by adding different amounts of sodium tetraborate (saturated borax solution). Figure 1 shows how the sodium tetraborate, the active ingredient in borax, facilitates the formation of tetrahydroxy borate through a boric acid intermediate (Note: A chemical intermediate is a reaction product of one or more steps in a step-wise reaction that is not a final product in the chemical reaction. Typically, chemical intermediates are quite reactive. These chemical intermediates help explain the step-wise mechanism for the formation of the borax cross-link detailed in Figure 2.)
The step-wise mechanism in Figure 2 shows how sodium tetraborate in water produces boric acid. In the first step, sodium tetraborate dissociates into sodium cations and tetraborate anions. The tetraborate anion reacts with water to produce boric acid and two hydroxide anions. Then the boric acid reacts with one hydroxide ion to produce tetrahydroxy borate anion. The tetrahydroxy borate anion reacts with two alcohol groups in the poly(vinyl alcohol) backbone to make two covalent bonds linking the tetraborate ion with one polymer chain. The two remaining hydroxyl groups attach to the boron and then react with two additional alcohol groups within an adjacent polymer chain. This reaction completes the borax cross-link and creates a covalent bond that links these polymer chains together. As the amount of tetrahydroxy borate anion shown in the third step-wise reaction increases, a higher probability exists to form more borax cross-links within the poly(vinyl alcohol). When creating their putties, students can increase the amount of tetrahydroxy borate anion by adding more sodium tetraborate solution or by stirring more vigorously to disseminate the tetrahydroxy borate anion throughout the poly(vinyl alcohol) matrix. Either way, by forming more cross-links between poly(vinyl alcohol) chains, the material properties of the poly(vinyl alcohol) change, allowing students to witness their ability to influence the putty material properties.
Before the Activity
With the Students
Formulation 1: 4% Poly(vinyl alcohol)
Formulation 2: Glue, 20% Poly(vinyl alcohol)
Write on the classroom board the table in Figure 3. Direct students to record their observations about the starting reagents and each polymer formulation produced. Record these observations in bullet or picture form. Be sure to include any observations about the starting reagents before mixing and then record all observations after the two reagents are mixed. Use these observations to help your team create a better formulation for the design challenge.
(Note: Student responses will vary. In order to do develop a solution to this engineering design challenge, students should experiment with different ratios of poly(vinyl alcohol) and saturated sodium tetraborate (borax) solution. Depending on how they manipulate this ratio, the properties of their polymeric material change from either stretcher to bouncier.)
Attachments (Return to Contents)
Safety Issues (Return to Contents)
Investigating Questions (Return to Contents)
Assessment (Return to Contents)
In-Class Questions: Quiz students on the material presented to them in the associated lesson. Listen to their answers to gain a sense of their familiarity with the topic.
Activity Embedded Assessment
Worksheet: During the activity, have students fill in their worksheets. Review their answers to gauge their comprehension.
Design Challenge Reflection: Have students answer the following questions. Review their answers to gauge their comprehension of the material.
Activity Extensions (Return to Contents)
At the point when students have completed the two primary polymer formations, pause and discuss as a class how these two formulations differ and in what ways are they similar. Brainstorm several different ways to modify the experimental procedure to vary the formulation to change the properties of the material.
Have students think about the concentration dependence of the desired material properties using formulation 1 and 2. The percent concentration of poly(vinyl alcohol) in formulation 1 to formulation 2 is very different. What material properties do students think will result from using a larger percent poly(vinyl alcohol)? Does it yield putty that better fulfills the design criteria or is the degree of cross-linking more important to the final properties of the putty?
References (Return to Contents)
Borax. Part of Rio Tinto. Accessed August 8, 2011. http://www.borax.com
Ahluwalia, V. K. and Mishra, A. Polymer Science: A Textbook. Boca Raton, FL: CRC Press, 2008.
Alfrey, Tony. Slime. Science Experiments, Lucille M. Nixon Elementary School. Accessed August 4, 2011. (how to make slime) http://www.sci-experiments.com/slime/slime.html
ContributorsCherelle M. Bishop, Kate McDonnell, Jeramy Jasmann, Melissa M. Reynolds, Michael A. de Miranda
Copyright© 2013 by Regents of the University of Colorado; original © 2011 Colorado State University
Supporting Program (Return to Contents)CHIP GK-12 Project, Department of Electrical and Computer Engineering, Colorado State University
Acknowledgements (Return to Contents)
This work was developed by the Colorado Higher-Education Interdisciplinary Project (CHIP) in the Department of Electrical and Computer Engineering, based upon collaborative work supported by National Science Foundation grant no. 0841259. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.