Silly Putty

Silly Putty is a silicone plastic "clay", marketed as a toy for children by Binney & Smith Inc. It is known as Potty Putty in the UK. Another name is Tricky Putty. It was originally created as a scientific accident on the way to solving another problem: finding a rubber substitute for the United States during World War II.

Description

Silly Putty is sold as a 0.47 oz (13 g) piece of plastic clay inside an egg-shaped plastic container. It is an example of an inorganic polymer, noted for its many unusual characteristics. When pressed on comics pages or other newspaper media, the loose ink transfers to the Silly Putty, which is then able to be stretched out, a source of amusement for many children. It bounces, revealing its rubber roots, it breaks when given a sharp blow, it can flow like a liquid when it is slowly stretched, and will "melt" into a puddle over a long enough period of time.

These unusual flow characteristics occur because Silly Putty is a viscoelastic liquid. Viscoelasticity is a type of non-Newtonian flow, and indicates that the material will act as a viscous liquid over a long time period, but will act as an elastic solid over a short time period. Silly Putty has sometimes been characterized as a dilatant fluid; however according to the science of rheology this is not strictly correct; it is more accurate to characterize it as a viscoelastic liquid. Silly Putty is primarily composed of the polymer known as polydimethylsiloxane (PDMS), which is known for its dramatic viscoelastic character.

Since the 1980s, Silly Putty has been available in various colors, including glow-in-the-dark and metallic, and colors can be easily combined to make new color shades. The brand is owned by the Binney & Smith corporation, which also owns Crayola crayons.

Origins

The origins of Silly Putty are controversial, as is typical of many inventions. Two researchers, working independently during the same time period, both came upon the product separately. The world may never know who was actually first.

Silly Putty was accidentally invented by James Wright of General Electric when he dropped boric acid into silicone oil. He was looking for a substitute for artificial rubber. GE supplied the newly discovered dilatant compound to researchers around the world. None found a use for it, but they all loved playing with it.

In 1943, Dr. Earl Warrick left the Mellon Institute of Industrial Research to join the newly formed Dow Corning Corporation. His research was refocused: help the war effort by developing a synthetic rubber substitute. Although he failed to produce a suitable rubber before the end of the war, one result of his experiments was a silicone bouncing putty.

The product was then commercialized by Peter Hodgson in 1949 after the marketing expert attended an informal "nutty putty" party. Renamed "Silly Putty" because of its main ingredient, Silicone, the product was a smash hit.

Raw Silly Putty polymer is available as Dow Corning 3179 Dilatant Compound. There are recipes for homemade silly putty using Elmer's Glue and boric acid. These produce a compound which is similar in chemical structure but is different in the elements which form that structure.

According to an MIT webpage on inventions:

Ironically, it was only after its success as a toy that practical uses were found for Silly Putty. It picks up dirt, lint and pet hair, and can stabilize wobbly furniture; but it has also been used in stress-reduction and physical therapy, and in medical and scientific simulations. The crew of Apollo 8 even used it to secure tools in zero-gravity.

Variations

Other brands

Thinking Putty, is marketed as an exercise and stress-relief 'toy' for adults, by Crazy Aaron's Puttyworld. Thinking Putty is essentially the same product as Silly Putty, both products using the same base substance, Dow Corning's 3179 Dilatant Compound. Crazy Aaron adds additional colorizing ingredients to this base substance to create the final product. These coloring agents can sometimes give the putty a slightly different texture than the traditional coral-colored Silly Putty, which tends to be a bit stiffer.

Crazy Aaron sells heat sensitive color changing putty, glow-in-the-dark putty, black magnetic putty, and regular colored putty in many hues. It is sold in 1/5 pound metal tins and 1 pound plastic bags. ThinkGeek sells a rebranded version, called 'Smart Mass Thinking Putty' in 1/5 pound tins.

"Homemade" variety

An undergraduate chemistry experiment is the production of silly putty; this is done by treating a solution of dimethyldichlorosilane in diethyl ether with water (Warning: the reaction of dimethyldichlorosilane with water is violent and generates hydrochloric acid). After washing the ether solution of the silicone oil with aqueous sodium bicarbonate, the solution is dried before the ether is evaporated off. Powdered boric oxide is added to the oil and then heated to form the Silly Putty. The Silly Putty has boron based crosslinks between the polymer chains. These boron crosslinks can break and form only slowly, hence when the silly putty is hit with a hammer or thrown at the floor it shatters or bounces but when the solid is left for a time in a tray it slowly flows.

Other "homemade" variants exist, branded under various trademarks and sold via the Internet.

Removal

Silly Putty will stick to soft plastics, rugs, and clothing, but can be removed using rubbing alcohol or baby wipes.

External links

- Treating dimethyl silicon polymer with boric acid
- Process for making puttylike elastic plastic, siloxane derivative composition containing zinc hydroxide
Official Website of Silly Putty
Full story at MIT's Invention Dimension: Silly Putty page
Various scientific experiments done with Silicone Putty
American Chemical Society "What's that stuff?" page about Silly Putty
Dropping a 50lb beach ball-sized sphere of Silly Putty off a parking garage (pics and video)
Crazy Aaron's Puttyworld: Thinking Putty