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Fluoroelastomer: The Fashionable New Darling of Watch Straps-Part 2

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The previous article on fluoroelastomer introduced its development and classification. This article will introduce the properties of fluoroelastomer and its comparison with silicone rubber.


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1. Main Properties of Fluoroelastomers

The material’s composition of monomers can be customized to provide a boost to its attractive properties, changes such as:

  • Improved temperature resistance (both low and high)
  • Good oil and grease resistance
  • Excellent resistance to aggressive oxidation, acids, fuels, or chemicals
  • Good resistance to extreme environments
  • Low compression set
  • Low gas absorption rate
  • And more

Fluoroelastomers have extraordinary resistance to most fluids at high temperatures. The material can withstand extreme temperatures with a useful service life above 473°F/225°C, chemicals, heat, and oil. For these reasons, Fluoroelastomer has become one of the most widely used materials to create O-rings and seals.

Though, keep in mind that all types typically have limited resistance to methanol, hot water (above 212°F or 100°C), steam, and other highly polar fluids. The other main drawback of this family of materials is its intolerance to low temperatures (limit of -22°F or -30°C). 


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Here are a few highlighted properties:

High-Temperature Resistance

Fluoroelastomers can maintain their elasticity and physical properties under extremely high temperatures, even briefly operating at temperatures up to 300°C. They remain resilient at temperatures around -20°C. The high-temperature stability makes fluoroelastomers an ideal choice for various applications in high-temperature environments, such as automotive engine seals, aerospace components, and petrochemical equipment.

The presence of fluorine atoms endows fluoroelastomers with excellent high-temperature resistance and stability. However, it also reduces the flexibility of the entire polymer chain, increasing rigidity, and leading to poorer performance in low temperatures.

Corrosion Resistance

Fluoroelastomers (FKM) typically refer to fluoroelastomers with a fluorine content of 66%. The chemical resistance of fluoroelastomers is closely related to their fluorine content. In general, a higher fluorine content correlates with stronger resistance to chemical corrosion.

Fluoroelastomers demonstrate superior corrosion resistance compared to other rubber types, with resistance to various chemicals, including acids, alkalis, organic solvents, and oils. This makes them an ideal material for use in corrosive environments in industries such as chemicals and petroleum.


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Weather and Ozone Resistance

Fluoroelastomers demonstrate outstanding resistance to weather ageing and ozone, enduring erosion from ultraviolet radiation, oxygen, moisture, and certain chemicals. This advantage makes fluoroelastomers ideal for outdoor applications and prolonged exposure to harsh environments. Even after natural storage for 10 years, fluoroelastomer products maintain satisfactory performance.

Mechanical Properties

Fluoroelastomers boast excellent physical and mechanical properties, including good tear and elongation at break.


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2. Comparison between Silicone Rubber and Fluoroelastomer

Silicone rubber and fluoroelastomer are two different types of elastomers or synthetic rubbers. These materials are commonly used in applications requiring flexibility, durability, and heat and chemical resistance.

Silicone rubber is an elastomer composed of silicone. Silicone is different from silicon: silicon is an element, while silicone is a polymer that contains silicon, together with carbon, hydrogen, and oxygen.

Silicone rubber boasts excellent resistance to high and low temperatures, chemical corrosion, and electrical insulation. Consequently, it finds extensive utility across the medical, food processing, electronics, and chemical sectors. Moreover, owing to its suppleness, durability, and ease of maintenance, silicone rubber is favored for crafting watch straps, bracelets, phone cases, and sundry products.


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So what are the differences between fluoroelastomer and silicone rubber?

Cost Comparison: 

Fluoroelastomer is more expensive than silicone rubber because the fluorine materials used are more costly.

Heat Resistance:

Both fluoroelastomer and silicone rubber offer excellent heat resistance among existing rubbers. Nevertheless, fluoroelastomer typically outperforms silicone rubber in this regard, rendering it more suitable for long-term exposure to elevated temperatures.

Chemical Resistance:

While both fluoroelastomer and silicone rubber are resistant to various chemicals, there are some key differences between the two. Fluoroelastomer generally showcases heightened resistance to oils and fuels, whereas silicone rubber excels in water and heat resistance. In terms of specific chemicals, fluoroelastomer is more resistant to acetic acid, acetone, and mineral oils, while silicone rubber is more resistant to benzene, freon, and peroxides.


Both fluoroelastomer and silicone rubber are highly durable. Nonetheless, fluoroelastomer tends to be more durable than silicone rubber, while silicone rubber is more flexible and has a lower density.

The suppleness of fluoroelastomer decreases compared to silicone rubber due to its chemical bonds. However, nuanced alterations stemming from the inclusion of diverse fluorinated monomers may engender variations in fluoroelastomer flexibility, resulting in differing characteristics across watch strap brands.

Additionally, fillers, additives, and processing techniques can also lead to variations in the mechanical, thermal, and environmental performance of fluoroelastomer watch straps.


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Today, more and more brands are turning to fluoroelastomer watch straps. They perfectly address the shortcomings of traditional leather straps, especially in terms of waterproofing and resistance to dirt. Some people initially find little difference between fluoroelastomer and cheaper silicone watch straps. However, after some time of use, the differences become apparent.

Fluoroelastomer exhibits superior resistance to oil, does not yellow or attract dust, and is easy to clean. Moreover, fluoroelastomer boasts higher hardness and density, with greater tensile strength, tear resistance, and abrasion resistance. Through adjustments in synthetic formulations and manufacturing processes, fluoroelastomer can even be made softer than silicone, ensuring a more comfortable wearing experience.

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