Silicone or Rubber — Which Elastomer Is Right for Your Project?

In the process of design of a new product, the choice of elastomer is usually one of the most important initial decisions. Regardless of whether you are coming up with a consumer product, a medical device, a car part, or an industrial tool, silicone or rubber might make a big difference in terms of performance, durability, cost, and regulatory compliance. Although both materials belong to the general group of elastomers, they have vast differentiation regarding the properties and application. These differences could be understood to assist engineers, manufacturers, and designers to make smarter and efficient decisions.

To make this decision, we have broken down the strengths, limitations and optimal applications of both materials below.

Knowledge Base: What Are the differences between Silicone and Rubber?

Silicone and rubber are commonly combined together due to the fact that they exhibit similar elastomeric behaviour, i.e. elasticity, flexibility, and deformation resistance. Nevertheless, they differ in terms of their chemical structures.

Silicone is an artificial elastic material that is composed of Silicon, oxygen, carbon, and hydrogen. It is anchored on siloxane chains which provide stability at a wide temperature range. Silicone may be designed in the form of liquid silicone rubber (LSR), high-consistency rubber (HCR) or room-temperature vulcanizing (RTV). This flexibility is used in the production of all types of products, whether it be a baby product or a medical implant.

Rubber can be natural, however, (NR), or synthetic (SBR, EPDM, NBR, neoprene, etc.). Every type of synthetic rubber has its performance profile. The chains of hydrocarbon-based structure of rubber render it harder in general, more abrasion-resistant and less expensive in terms of its industrial and automobiles uses.

In short:

• Silicone gives priority to stability, safety and extreme temperature stability.
• Rubber values strength, toughness as well as economic value.

Comparison of Performance: Temperature, Durability and Environment Resistance.

To select the appropriate elastomer, one needs to have a realistic idea of what operating conditions your product will be exposed to. The following are the performances of silicone and rubber with regard to important parameters:

Temperature Resistance

Silicone: Outstanding thermal capabilities. Its temperature range is between -60C and +230 C and certain formulations can go even higher. Silicone does not break with the changing temperatures and will not decay.

Rubber: The type is dependent on temperature tolerance. Natural rubber hardens in cold conditions and decays around 100 o C. Silicone has better upper performance than specialty rubbers such as EPDM and fluorocarbon (FKM), which are very rare.

Silicone is best used in high temperature or rapid cycling.

Chemical & UV Resistance

• Silicone: This compound is very resistant to oxidation, UV radiation, ozone and most chemicals. It is not yellow readily, and does not readily break down in the open air.
• Rubber: Mixed performance. EPDM is resistant to UV whereas natural rubber deteriorates rapidly in the sunlight. NBR is excellent with oils, fuels hence it is also suitable in automotive.

Best where it is needed outside or in hospital: Silicone.

Tear, Abrasion and Mechanical Strength.

• Silicone: Soft and flexible and good cushioning(however not as mechanically strong as rubber). Unless reinforced; it can easily tear during heavy loads.
• Rubber: Good tensile and sufficient abrasion. Natural rubber continues to boast of one of the best elastic materials in terms of mechanical performance.

Most suitable when there is high stress: Rubber.

Compression Set Performance & Sealing Performance.

• Silicone: Shows remarkably good performance by not deforming after repeating compression, which is suitable in the gaskets, O-rings and seals that are subjected to dynamic temperature.
• Rubber: Compression characteristics are good with possible loss of elasticity at high exposure to heat under extended heat conditions.