閱讀筆記 S4016 A Sticky Situation

Science 4016
A Sticky Situation
Who made rubber the useful material that it is today?
lf you look around, you can probably spot at least a few things that are made of rubber—a ball, the bottoms of your sneakers, the wheels of a car. Without the patience and work of Charles Goodyear, none of them would have been possible.
Rubber begins as the sticky sap of a tropical tree. In the early 1800s, people thought that this waterproof material was the wave of the future. They were eager to use things made of rubber. It wasn’t long, though, before they realized that rubber wasn’t as useful as it first seemed. When it got cold out, rubber froze and became brittle. When it was hot, rubber melted and turned into a gooey mess. Suddenly, no one wanted to use rubber products anymore.
Charles Goodyear was fascinated with rubber. He was sure that there was a way to make it stable and easy to use. He began to work with the rubber gum, kneading it and rolling it out. He experimented with it by adding different materials. He thought that he might be able to add a powder to the rubber that would keep it from getting so sticky in the heat. The first type of powder he added was called magnesia. He made shoes from this rubber, but they melted. Goodyear needed to try something else.
The next time, he decided to experiment with magnesia and something called quicklime. He boiled the mixture and got a slightly better result. However, he found that when this rubber touched even a mild acid, like lemon juice or vinegar, it was ruined.
Others might have given up, but Goodyear knew he could find a solution to the problem. He added nitric acid and found that the rubber seemed smoother and drier. He was sure that he had made a better product. Sadly, he was wrong. The mailbags he made of this new rubber melted in the heat, too.
After years of work, Goodyear learned that sulfur might help dry out the rubber. He made the mixture and kept on experimenting with it. One day, a piece of it accidentally dropped onto a hot stovetop. Instead of melting, it turned tough and leathery. When the mixture of rubber gum and sulfur was heated at a high temperature, it became stable. Goodyear had finally found a solution!