Silly Putty

From Chempedia

The Art & Science of Silly Putty

What a package of Silly Putty looks like today.

1 A Brief Introduction
2 History
3 Silly Putty Chemistry
4 Conclusion
5 Works Cited
6 Footnotes

A Brief Introduction

In 1943 James Wright stumbled upon a silicon-based mixture that is today known as Silly Putty. Originally sought after as a substitute for rubber, the substance didn’t possess the desired properties as a replacement. Instead, it was found to have some unique properties derived from its distinctive chemical structure. In 1949, the product was purchased by a toy store, which sold the product as a novelty item. They marketed the product as "Silly Putty." Today, Silly Putty is widely known among both the young and old.

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History

During World War 2, the army was running low on rubber. To fix this problem the government asked the scientists of the day to start research on a synthetic rubber compound. James Wright, who was working for General Electric at the time, accidentally added silicon to boric acid in his laboratory. The substance made had unique properties, and after testing the new substance in various ways, he bounced it on the floor. To his surprise, it bounced very well. Unfortunately, due to its consistency, the substance wasn’t able to be used as a substitute for rubber, but still had potential.

In 1949, Ruth Fallgatter, a toyshop owner, decided to sell Silly Putty in her store. The product became a popular item from the store; it was only out-sold by crayons. After one year, Fallgatter discontinued selling Silly Putty. Peter Hodgson realized his chance to market this new product. He sold the 1 oz. Putty in the plastic egg-shaped containers that are sold, even today. These newly marketed eggs still didn’t receive widespread attention until a magazine article on Silly Putty was published in the New Yorker. Soon after, Silly Putty had orders from all around the country, selling more than anyone could’ve imagined. Shortly after, a commercial debuted and Silly Putty started to be sold around the world. It was even taken to the moon with the Apollo 8 astronauts. Today new and better silly putties are being invented, including color changing Silly Putty.

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Silly Putty Chemistry

The reason that Silly Putty is so popular is because of its properties formed by its unique molecular structure. The main structure of Silly Putty is polydimethylsiloxane, which is a polymer (a long repetitive chain of molecules). These polymers form layers, which are linked together by boric acid. This cross-linking connects most of the polymers together, but not all of them, creating the possibility of movement when force is applied (the diagram to the right shows the boric-linked-polymers that make up Silly Putty). The molecules

The molecular structure of Silly Putty. Note how the boric acid links thepolymers together.

that make up the polymers are covalently bonded, where as the molecules, themselves, are linked by hydrogen bonding to boric acid. When stress is applied to the putty the viscosity (resistance to flow) is affected. Silly Putty’s viscosity is not only dependent on temperature, but also stirring or spreading can also change it. This process causes the Silly Putty’s viscosity increases under increased stress.

Through this unique structure, Silly Putty has many unexpected properties. One such property is its ability to bounce well. This happens because it is actually a mix between a liquid and a solid. Silly Putty has a property called viscoelastic, which makes the silicon based plastic both a liquid and a solid. For example, when Silly Putty is just sitting in place, it will keep its shape. On the other hand, when force is applied, the Silly Putty will deform to the new force. This curious behavior can be explained by its molecular structure.

At the molecular level, the cross-linking connects most of the polymers together, however not all of the polymers become connected. This, in turn, creates a structure that can stand on its own, but not to applied outside forces. When the Silly Putty drops to the ground, the cross-linked polymers are too intertwined to make the Silly Putty completely flat. The polymers make the putty have more elasticity than it would otherwise. When the putty starts to bounce back, the cross-linked polymers go back to their original state, essentially ’pushing’ the putty off the ground.

Another behavior produced through Silly Putty’s cross-linked polymers is its ability to shatter when hit with great force, but inversely molds to a weak force. In the situation of a large force, the cross-linked polymers are being affected too quickly to condense, so they shatter. With the smaller force, these polymers are allowed time to shift before the break. This is one of Silly Putty’s most unique properties.

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Conclusion

Overall, Silly Putty has a unique origin and a long and profitable history. However, breaking down and examining its cross-linked polymer structure easily explain the most unique things about Silly Putty. Though, in the end, Silly Putty wasn’t an applicable substitute for rubber, but instead, it found use as a novelty item for children worldwide.

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