Kalrez KLX-16011Gallagher Fluid Seals is a longtime partner of DuPont®’s, having specified thousands of DuPont perfluoroelastomer parts over the past few decades.

While elastomers were originally created as an alternative to natural rubber, they have expanded to include materials such as high-performance perfluoroelastomers for demanding applications.

These materials can also be used in place of plastics in most, if not all, applications. DuPont is at the forefront of perfluoroelastomer development, creating elastomers with properties that can help meet highly specific application requirements.

Read on to learn more from Dupont about the differences between elastomers and plastics, and how elastomeric seals perform compared to plastic seals.

Important Concepts

  • How elastomers differ from plastics
  • How high performance elastomers differ among themselves and from lower performance elastomers.
  • How high performance elastomers perform as they do.
  • How factors other than elastomer selection determine seal performance.
  • Why elastomers perform well or fail in some environments.
  • How various factors influence the compatibility of elastomers with process fluids.
  • How to assess the relative value of high performance fluoroelastomer seals.
  • How to select the "best" elastomeric sealing material for specific equipment and service.
  • Good specifications ensure that seals are made of the preferred elastomer.
  • Employ life-cycle costs to correctly measure a seal's value.

What Are Elastomers?

Elastomers are long-chain polymers connected by crosslinks. The crosslinks impart an "elastic" nature and provide resilient recovery characteristics. They are stable under heat or pressure.

What Are Plastics?

Plastics are long-chain polymers that are usually not connected by crosslinks. Plastics often acquire their properties and strength from crystalline regions that form when chain segments "line up" and crystallize.

These crystalline regions can form and/or melt under pressure and heat.  Thus, plastic can creep or extrude in service.

Choose Elastomeric Seals

Compared to plastic seals, elastomeric seals with stable crosslinks can impart excellent resilience and recovery, which:

  • Increases dimensional stability over a broad temperature range.
  • Maximizes compression set resistance.
  • Resists extrusion at high pressures/temperatures.
  • Retains sealing force during pressure/temperature cycling.

Elastomeric seals are versatile

Features of High Performance Elastomers

Standard ASTM D200 chart -- relative heat and oil resistance of elastomers (% Volume Swell in ASTM No. 3 Oil)

Volume Swell

Features of High Performance Elastomers

In addition to heat and oil, high performance elastomers are designed to resist a broad range of aggressive media at high temperatures for extended periods of time.

Aggressive Media (Example)

  • Aromatics (Toulene)
  • Aliphatics (Hexane)
  • Acids (Hydrochloric)
  • Bases (Sodium hydroxide)
  • Polar Solvents (Methanol)
  • Oxidants (Bleaching agents)
  • Hot Water (Pure or contaminated)
  • Steam (Pure or contaminated

Features of High Performance Elastomers

Retention of properties:

  • No elastomer degradation
  • Low volume swell
  • Retention of strength
  • Retention of elongation to break
  • Minimal change in hardness
  • Retention of sealing force during thermal cycling

Temperature resistance:

  • 150 degrees C to 300 degrees C
  • Intermittent or continuous

Service requirements:

  • Months to years
  • Intermittent or continuous

Strong chemical bonds enable high performance elastomers to perform in hostile environments. The fluorine-carbon bond is one of the most stable bonds in organic chemistry.

Bond Type   Approximate Bond Energy, kcal/m   Typical Elastomer

C-F               105.4                                                                    Vitron, Kalrez

C-H               80                                                                            Nordel

C-CL            78.5                                                                         Neoprene

High bond strength increases the thermal and chemical strength of elastomers.