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Silicone Engineering > Blog > Is Silicone a Rubber or Elastomer?

Is Silicone a Rubber or Elastomer?

You may have heard a number of terms for describing rubber-like materials such as polymers, elastomer and synthetics and thought what is the difference between them (if any at all)? Here we explain the difference between rubbers, synthetics, polymers and elastomers as well as focusing on our material – silicone. We explain what group silicone falls into to allow you to gain understanding when choosing a rubber material for application.

1. Rubber – Is essentially the original name given to Latex and is a natural product harvested from the rubber tree, shown in the picture below. Latex was the first “rubber-like” material invented and continues to be used in a number of applications today.

Rubber Tree

Rubber Tree

2. Synthetic – This just means something artificial or man-made. Synthetics are not naturally made unlike Latex.

3. Polymer – Is a large molecule made up of many repeated smaller units called monomers. A polymer can be natural or synthetic.

4. Elastomer – Is a polymer that displays elastic properties.

A part from Latex (the natural product), most elastomeric products fall into the category of “Synthetic Elastomer” the use of the word elastomer is used interchangeably with rubber nevertheless, Silicone is more correctly an “elastomer”.

What is an Elastomer?

As you can probably guess by our name, Silicone Engineering is a silicone elastomer manufacturer. This is where our expertise lies and has done since we first opened in 1959. In this section we will go into more detail about elastomers and in particular – silicone.

An elastomer is a polymer with viscoelasticity (having both viscosity and elasticity) and very weak inter-molecular forces, generally having low Young’s modulus and high failure strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber.

Each of the monomers which link to form the polymer is usually made of carbon, hydrogen, oxygen and/or silicon. Their primary uses are for seals, adhesives and molded flexible parts.

What is Silicone?

Silicone Elastomer, or to give it its scientific name – Polysiloxane, is an amazing material. It offers a unique combination of chemical and mechanical properties that organic elastomers cannot match.

Inorganic Synthetic Elastomer   Silicone Elastomer Polymer Chain

Benefits of Silicone Elastomers

Silicone elastomers have many benefits over other elastomers. These include:

  • Extreme Temperature Resistance
    • High and low temperature applications
    • +230°C continuous (300°C Intermittently)
    • -60°C
  • Excellent Environmental Resistance
    • Ozone
    • UV
    • General weathering (rain, snow, sleet, frost)
  • Low Compression Set
    • Good resistance to compression set at high temperatures
    • Great for sealing
  • Low level of combustible components
    • When exposed to flame, the elastomer is reduced to a non-conducting silica ash
  • High physiological inertness
    • Tasteless
    • Odourless
    • Non-toxic
    • Resistant to bacteria and fungi

Negatives of Silicone Elastomers

Although having many benefits, silicone also has some negatives depending on what job you need the material to do or withstand.

  • Poor Abrasion
    • If you are looking for an elastomer with good abrasion properties then we would generally advise silicone is not your material.
    • Hence the reason you don’t see car tires or soles of shoes made from silicone as their lifespan would be short
  • Poor Oil/Petroleum Resistance
    • Silicone is prone to swelling if in contact with oil for a period of time.
    • In this instance we would suggest a Fluorosilicone be used due to its oil/petroleum resistance

To conclude, choosing the correct elastomer or rubber is very much down to the application and what job you need the elastomer to do. Silicone is an amazing material if high temperatures and environmental pressures are present but as explained it will most likely fail if oil/petroleum is in contact. Therefore selection is key to ensure long lifespan in service.

If you really aren’t sure which elastomer would suit your application or would like some information on our range of specialist silicone grades, one of our experts will be able to answer the question. You can send your question in by clicking on the ‘Ask the Experts’ link below.

 

About the author

Simon Holmes
 

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