Vulcanization is the process by which natural rubber, tapped from trees, is transformed into a malleable product that is more durable and flexible. Vulcanization itself is named after the Roman fire god, Vulcan, which correctly suggests that the main bulk of this process heating. However, since heating the rubber itself is not sufficient, curatives and/or accelerators are needed to further change the chemical properties.
Natural rubber (isoprene) is not the best for molding products because its primary (linear) hydrocarbon structure gives the rubber limited mobility. Chances are, if you bend it the wrong way, it will break! We solve this problem by adding curatives like sulphur molecules, allowing the linear structures to bond together and form a much larger and flexible molecule. Specifically, cross-linking sulphur molecules creates disulphide bonds between the carbon molecules of two or more rubber structures in multiple areas, forming a tertiary structure: polyisoprene.
Another property gained through this process is the ability to stop the linear structures from moving independently, so that when the rubber changes shape, it can reverse back to its original shape.
The one issue with this process is its speed. While heating the rubber does increase the surrounding energy so that the sulphur can bond, the heat added isn’t quite enough for this process to be fast. This is where accelerators come in. Example of accelerators include catalysts like zinc oxide or stearic acid. Remember, all reactions require a certain amount of energy to perform. By using a catalyst, the amount of energy needed is lowered, which means less energy is used for the same reaction. This makes the process more efficient as more bonds can be formed with the same amount of energy. Accelerators are able to change the chemical bonds of the rubber to speed up the process and make it more efficient without affecting the outcome.
Plastics undergo a similar process in order to produce all the different shapes imaginable. For example, thanks to this process, polyurethane can come in many forms, ranging from tennis grips to wheels, woodwork glue, or foam bedding. Because of its flexible properties, polyurethane paint is also widely popular. Both water and oil based, it is used for busy indoor environments such as kitchen tops and bookshelves. The plastic aspect allows for durable use and abrasion-resistant properties. However, polyurethane paint should not be used in places that will be exposed to the outside environment, because it is temperature-sensitive, especially if exposed for long periods of time.
By Asta M., Staff Writer
Edited by Peggy K.