Elastomers in Product Development: Introduction To Engineering Elastomers

Elastomers are the hard-working hero of many a product design. In this series of posts, we’re exploring the flexible properties and use cases for a range of elastomers and examining their use in new product development.

Porticos has extensive knowledge and experience with the integration of elastomers into physical devices. We’re here to help; please get in touch!

It’s Not Rubber

Many products and devices include some kind of soft “rubber” element. Examples include:

  • That grip on your disposable toothbrush
  • Weather seals on handheld electronics
  • Fuel-line on a lawn mower
  • Plunger-seal on a hypodermic
  • Vibration-isolation on a kitchen appliance
  • Anti-slip feet on… just about anything
Sheets of natural rubber on a rubber tree plantation

Ironically, they are almost never actually rubber. Rubber is a specific and increasingly rare type of elastomer, a Vulcanized Thermoset, derived from the sap of the Hevea brasiliensis (rubber tree) or one of its cousins.

Early automobile tires, among many other things, were made of rubber until an artificial shortage (World War Two) incentivized research into synthetic alternatives. Those alternatives turned out to be superior to rubber in most ways, and the family of available “synthetic rubbers” grew to fill every niche. The word rubber has evolved to refer to any material with elastomeric properties.

What is an Elastomer?

In engineering terms, an elastomer is any polymer that can undergo very large strain without permanent deformation. One can stretch an elastomer to at least twice its original length; a strain of 100%.

Most elastomers exhibit other useful engineering properties as well…

  • Low Young’s Modulus, which means that a relatively low force is required to achieve deflection.
  • Viscoelasticity, allowing the material to absorb and damp out vibration.
  • High Coefficient of Friction, useful in anti-slip applications.
  • Negligible permeability, making them useful in fluid sealing applications.

Because so many elastomers have been optimized for sealing, they often have broad or rare chemical compatibility. In another quirk, elastomers are so soft that they have their own hardness scales: Shore Hardness. This property makes them valuable components in systems that protect devices or people from harm.

Thermoplastics and Thermosets

Room-temperature casting of thermosetting elastomer
Casting Process

Elastomers are polymers, and all polymers can be placed into one of two categories based on how they respond to being heated.

Thermosets

Thermosets, including natural rubber, start as a liquid mix. They undergo a chemical reaction called curing to “set up.” Once cured, applying heat will not melt the material. Examples of thermoset elastomers include:

  • SBR
  • NBR (Nitrile, Buna-N)
  • EPDM
  • Polyurethane
  • Silicone
  • Chloroprene (Neoprene)

Thermoplastics

Thermoplastic materials can be melted and then re-solidified, usually with no degradation of properties. Thermoplastic Elastomers or TPEs were developed to facilitate desirable manufacturing processes and to improve recyclability. The TPE family includes:

  • SBC (Styrenic Block Copolymers)
  • TPO (Polyolefin Blends)
  • TPV (Vulcanized Elastomer Blends)
  • TPU (Thermoplastic Polyurethane)

Which Elastomer is Best?

That’s what this series of posts is all about.

The best elastomer is the most cost-effective material that can meet specific requirements. Some combinations of requirements make the decision very simple. If you need a very soft material that can also resist high temperatures then there is really only one choice. (Psst. It’s silicone.)  

But most applications are less obvious. A diligent investigation will lead to a comparison based on both technical and economic factors. The next few posts will discuss the different ways of selecting the best material for your application.

Next Up

There are a dozen ways to make a “rubber” part, and each manufacturing process exists for a reason. We’ll explore pros, cons, strengths, and costs of each.

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About Porticos

A WORLD OF OPTIMIZED PRODUCTS

Porticos, Inc. is a Product Engineering and New Product Development firm located in Research Triangle Park, NC.

Established in 2003, Porticos produces innovative and effective solutions for their clients and the markets they serve. Porticos provides broad expertise in development, planning, and production. 

Contact us for more information or support bringing your idea to market.