Natural & Synthetic Rubbers - what are they and how are they used?

Natural rubber is produced from latex, tapped off a rubber tree. Uncured, this rubber has limited application (e.g. adhesives, cements, etc.) and is unlike our expectation of what ‘rubber’ should be. However, after undergoing mastication, blending, calendering, extrusion and finally vulcanisation, it becomes the product we know.

Natural rubber, or latex is used mostly in car tyres and medical products.

Vulcanised rubber is mainly used to produce automotive tyres, however there are a large number of additional applications, including seals and medical products (e.g. surgical gloves). Whilst some people are allergic to latex, it is also susceptible to bacterial attack, making natural rubber unsuitable in certain applications.

The most common synthetic rubber is silicone

Synthetic rubbers are petroleum based, and compared with natural rubber, currently provide the majority of rubber worldwide. There are many forms of synthetic rubber, and one such type, which is used in a number of industrial applications, is Silicone rubber. Others include Neoprene, EPDM, Viton and Nitrile.

Compared with natural rubbers, synthetic rubbers exhibit superior thermal stability, as well as improved compatibility with petroleum products. Similarly to natural rubber, synthetic rubbers are used mainly for tyres, seals, etc but have a larger number of consumer applications.

Silicone rubbers are used in many consumer and industrial applications

Silicone rubber is more resistant to heat, UV, chemicals as well as fungal and Ozone attacks than natural rubber. Consequently it has found many uses in, for example, cookware, involving bacteria, chemicals and heat.

Please refer below for physical comparisons between natural rubber and synthetic rubbers: 

There are 3 common processes

There are 3 common processes, and these can be used for both materials:

• Injection moulding – Using this process, thin wall sections are possible. Injection moulding is mainly used for high volume runs, on tight tolerance parts where the tooling can be justified.
• Compression and transfer moulding – Compared with injection moulding, tooling is less complex, and has a lower cost. These processes are most suited to low – medium volume manufacture. The cycle is labour intensive leading to multi-cavity tooling for higher quantities, to control the economics.
• Extrusion – involves ‘continuous vulcanisation’ where the rubber is extruded and vulcanised at the same time. Sharp edges on parts can cause rough surfaces to be produced, and radii would need to be applied. Co-extrusion allows multi-material parts to be produced.

As a consequence of the quantities that Plunkett Associates are usually involved with, compression moulding is the most applicable for:

• prototyping where production materials are required, and
• low volume production.

If your project requires a rubber part, please talk to us. We are able to help.