Wednesday, December 19, 2012
Rubber is an amazing invention. It can be used in a number of remarkably different applications because of its versatility. Natural rubber, for example is extremely elastic. It can oftentimes be found in products where its unique flexibility is desired like rubber bands or some types of gaskets. It can also be found in some types of specialty flooring. However, natural rubber is also brittle when it gets cold and tends to lose shape when warm. It is for this reason that vulcanization is required for the manufacture of many rubber products. (Many products such as rubber flooring, tires, and hockey pucks are created from vulcanized rubber.)
The process was initially pioneered by Charles Goodyear (of Goodyear Tire fame.) He found, accidentally, that rubber tended to char like leather when it came in contact with heat. He also found that, regardless of the temperature, the rubber would not fully melt but rather continue to char when heated in sulfuric acid. He was able to char the rubber to the point where it became resistant to heat and cold and found that the process was irreversible. The rubber would maintain these new properties indefinitely. This made rubber products such as tires and eventually rubber flooring possible. Further developments after Goodyear’s initial experimentation eventually led to vulcanization as it is performed today.
Vulcanization is a chemical process that cures rubber or related polymers into more durable materials by adding various accelerators (which is sulfur in most cases.) These additives change the polymer by forming crosslinks between the individual polymer chains. The process was named after Vulcan, Roman god of fire. Hard vulcanized rubber is used to make hard rubber articles such as bowling balls and mouthpieces for band instruments. Vulcanized rubber materials tend to be less sticky and have superior mechanical properties to natural rubber.
There are a variety of methods used for vulcanization. The most important method (used for the vulcanization of tires) uses high pressure and temperature. This type of vulcanization is called compression molding. In this scenario, the rubber article adopts the shape of the mold. Other methods, for instance to make door profiles for cars, use hot air vulcanization or microwave heated vulcanization.
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