What happens when natural rubber is vulcanized

What is vulcanization?


vulcanization refers to a process in which rubber (latex) is made resistant to pressure and heat. Before the American Charles Goodyear discovered vulcanization, rubber and latex products were often unable to withstand weather conditions. They became porous or stuck together. This process from 1839 made rubber weatherproof and one of the most widely used raw materials in the world. Today vulcanized rubber is used for car tires, tubes and latex mattresses.

Nowadays vulcanization is used for all processes by which rubber is brought from the state of predominant plasticity to a state that has a higher plasticity.

Process of vulcanization

The aim is to obtain rubber through the process of vulcanizing. During vulcanization, Rubber with sulfur and some other substances mixed and heated. The temperatures are at 120 ° C to 160 ° C whereby the long-chain rubber molecules are connected by the sulfur. The ratio of sulfur to rubber during vulcanization is approximately 2% / 98%. The sulfur content is therefore comparatively low. This connection with sulfur (called sulfur bridges) enables the rubber to transition from a plastic (weather-unstable) to an elastic (weather-resistant) state.

The result is rubber. - This is:

  • more elastic,
  • more tear-resistant,
  • more stretchy and
  • more independent of the weather than untreated rubber.

The more sulfur bridges the rubber contains, the harder it is. The number of these bridges depends on the duration of the vulcanization and the amount of sulfur added.

In addition to the chemical fillers and reactants, devices and machines are also required for heating the rubber or rubber:

  • Vulcanizing kettle: This is used to vulcanize hoses, sheets, injection molded articles, shoe parts and tires. They are available in vertical and horizontal versions. The so-called autoclave is a classic vulcanizing kettle.
  • Vulcanizing presses: They are used to heat tires, plates, conveyor belts and technical rubber goods. For the desired result, the press must be adapted with the respective article. There are several types of vulcanizing presses. There is once that Deck press for technical molded articles, sheets and there are those Special press for belts and conveyor belts etc. With the usual Vulcanizing presses the products are always vulcanized in frames, sheets or in molds. The multi-stage press is often used because it can be used to heat several molds and plates that lie one on top of the other at the same time.