Rubber is a polymer that arises as an emulsion (known as latex) in the sap of various plants, although it can also be synthetic. After coagulation, it is a very elastic waterproof mass with many applications in industry. Latex is mainly extracted from the Hevea brasiliensis native to the Amazon, although it is also extracted from other plants. The tree that provided the rubber only grew in South America, although it later spread. Michael Faraday, after research, managed to find out that rubber was formed by hydrocarbon chains and thus it was known that it was possible to create synthetic rubber.
Applications of rubber
Rubber is used to create many items with different uses. Its main use is in the manufacture of tyres, rims, waterproofing and insulating materials. It is also used, although it is not very common, to make clothing.
It has very good elastic properties, is resistant to acids and alkaline substances, is resistant to water, and insulates against electricity and temperature. Finally, it dissolves easily in petrolatum, benzene and some hydrocarbons.
Natural rubber is vulcanised (heated and sulphur or selenium is added), which makes the elastomer chains bond and improves its elasticity and resistance to temperature changes. There is also cold vulcanisation in which the rubber is immersed in a sulphur monochloride solution.
Today most of the rubber produced is synthetic, although natural rubber is still used.
Rubber working techniques
The techniques for working rubber are as follows:
- Compression moulding: the raw material (powder) is put into a heated mould (140-160°C) and subjected to high pressure. After a few minutes, it is plasticised and cured in the mould and then the part is removed (electrical switches and fuse holders, machinery...).
- Transfer moulding: this is similar to the previous process. In this case, the raw material is preheated before being put into the mould and transferred hydraulically.
- Injection moulding: the raw material is placed in a hopper and due to gravity falls into the machine. It is injected under pressure into the closed mould with a heated screw at a temperature lower than that of the injected raw material. The part is then removed. Suitable for the production of products in large quantities.
- Dehumidification process: through an automatic system. The raw material to be used is placed at the desired humidity levels, specific to each material and the product to be manufactured.
- Mould temperature controllers: is a system whereby the temperature controllers decrease or increase the mould temperature in the pre-moulding process. Depending on the raw material used, the mould has to reach a different temperature.
Rubber recycling is very important because millions of tyres are used and discarded worldwide. In fact, a tyre takes many years to decompose and rubber is a pollutant (it is flammable, emits harmful gases when burned and its accumulation makes it a source of infection). The most commonly used method of recycling synthetic rubber is mechanical shredding, which produces various end products for the market. It can be used as insulation for vehicles, carpets, rugs...It has a wide range of uses.
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