While elastomeric materials are utilized by multiple industries, including automotive, construction, medical devices, and consumer products, very few people understand what elastomers really are, how they act when they experience stress, or why elastomers are selected over rigid plastic and metallic materials. This ultimate guide from WM F McGraw provides an in-depth understanding of the nature of elastomeric materials, their properties, how elastomers function, as well as the leading industries in the United States that utilize elastomeric materials.
As technological advancements continue to increase and fuel the development of materials in society today, elastomers provide much-needed flexibility, resilience, and long-term strength that traditional materials cannot provide. You will develop an understanding of the physical properties and molecular structure of elastomeric materials, their molecular function, and the ways in which elastomeric materials impact specific industries.
What Are Elastomeric Materials?
Elastomeric materials (commonly referred to as elastomers) are polymers that utilize a process referred to as viscoelasticity, which means that both viscous (i.e., thick liquid) and elastic (i.e., rubber band-like) behaviors are exhibited. Unlike rigid plastics, elastomers are capable of being elongated significantly when stressed and, upon removal of that stress, will return to their original unstressed state.
The physical elasticity of elastomers is attributed to their molecular characteristics, whereby they are composed of very long chains. When stretched, the chains of these materials start to separate from one another. Then, when you stop exerting force on the material, the crosslinks that interconnect the polymer chains pull the chains back together.
How Do Elastomeric Materials Work?
Elastomers Have a Molecular Structure That Makes Them Elastic
At the molecular level, elastomers comprise long chains of polymer molecules, all connected via crosslinks. The crosslinks provide a bonding point in each chain, thereby allowing the chain to be extended (by elongation, compression, bending, etc.) and to return to its original shape as a result of a force acting upon the entire chain of polymer molecules.
When the polymer chain is subjected to a force (for example, by stretching or bending), the polymer chain elongates or becomes longer than when not subjected to a force. Because the crosslinks in the polymer chains keep them from flowing, the elastomer does not act as a fluid, but as an elastic solid that, after having been deformed and then relieved of load, will return to its original shape. This dynamic elasticity is why elastomeric materials are so important for dynamically loaded applications or applications that require load support.
Elastomeric Materials Have Good Flexibility and Do Not Require Specific Temperatures to Maintain Their Flexibility
Elastomers maintain their flexibility over a wide range of temperatures. Unlike thermoplastics, which become brittle at low temperatures or melt at high temperatures, many elastomeric products behave as if they have retained their flexibility.
Elastomeric materials are typically used in many different applications that experience temperature fluctuations, including automotive applications, outdoor sealing applications, and industrial applications that experience significant temperature variations.
Elastomeric Materials Have Three Key Properties
One of the key properties of elastomers is their ability to withstand and recover from deformation. Another key property of elastomeric materials is their ability to absorb energy. When elastomers are subjected to an impact, they can deform enough to absorb the energy of the impact, whereas other materials would break upon impact.
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Shock Absorption, Vibration Isolation, and Protection
Elastomers are used to absorb shock, form protective bumpers, make shoe soles, and serve as vibration pads for heavy machinery, which help cushion against impacts.
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Chemical Resistance & Weather Resistance
Most types of elastomers resist oils, solvents, ozone, and UV light, making them well-suited for outdoor or industrial applications where they are exposed to harsh environments.
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Flexibility at Low Temperatures
There are many elastomers that remain flexible at very low temperatures; therefore, this characteristic is important for outdoor products, automotive parts in cold temperatures, and aerospace components.
Silicone and some fluorosilicone elastomers continue to perform well at subzero temperatures and do not become brittle at these temperatures.
Examples of Commonly Used Types of Elastomers
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Natural Rubber (NR)
Natural rubber is obtained from the latex of rubber trees. It has exceptional resilience and elasticity. Therefore, natural rubber is frequently used in tires, hoses, and vibration mountings. However, while NR has excellent mechanical properties, it will break down when exposed to oil and ozone without the protection of additives or compounds.
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Synthetic Elastomers
Synthetic elastomers are manufactured rubber materials that are designed for specific applications and performance characteristics. Examples of synthetic elastomers are:
Nitrile Rubber (NBR) is resistant to oils and fuels and is commonly used in automotive and industrial sealing applications.
EPDM is commonly found in roofing materials or automotive weatherstripping because of its superior weather and UV resistance.
Silicone is flexible over a wide range of temperatures and is commonly used in medical applications, cookware, and aerospace applications.
Neoprene provides good weather and abrasion resistance; therefore, it is commonly used in industrial gaskets and protective clothing. Fluoroelastomers (such as Viton®) are known for their resistance to chemicals and heat and are utilized in seals found in vehicle fuel systems and in harsh chemical environments.
Synthetic elastomers each have their own strengths, so making the right choice of elastomer depends on how it will be used.
How Elastomeric Materials Are Made
Elastomeric polymers are blended and compounded with other materials that can include fillers, plasticizers, stabilizers, and other additives to achieve desired properties. The compounding process allows for tailoring the base polymer to meet the performance requirements of the intended application.
The following properties will be established during this process: hardness, tensile strength, flame resistance, and chemical resistance. Once the elastomers have been compounded, they can be successfully processed into a finished product using various manufacturing processes, including:
- Compression Molding: Material is forced into shape by heat and pressure after being placed into a heated mold.
- Injection Molding: Elastomers can be processed into specialty products by being injected into intricate molds under controlled heat and pressure.
- Extrusion: This method is appropriate for making products with continuously uniform cross-sections, such as tubing, seals, and weatherstripping.
All three methods provide dimensional accuracy and consistency in elastomeric materials, making them suitable for the production of complex industrial products.
How Elastomeric Materials Are Used
Elastomeric materials are an integral part of many automotive applications, such as tires, hoses, engine mounts, weatherstripping, and vibration dampers.
Their resilience and durability in maintaining their desired physical properties when exposed to rapid temperature changes, frequent vibration, and chemicals make them essential for maintaining safety and comfort in vehicles.
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Construction and Infrastructure
EPDM and neoprene elastomeric materials are typically used to manufacture roofing systems, sealants, expansion joints, and waterproofing systems. Elastomeric materials play an important role in building envelopes because they are weather-resistant and remain elastic.
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Consumer Products
Elastomers are commonly used in footwear, sports equipment, wearable electronics, and seals found in homes.
Due to their comfort, flexibility, and ability to absorb shock, elastomers are ideal for products that come into contact with the human body.
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Medical & Health
Medical elastomers and silicone are used for various medical devices, such as tubing, seals, implants, and flexible components.
For medical applications, elastomeric properties such as biocompatibility, sterility, and temperature performance are critical.
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Aerospace & Automotive
Elastomers perform under extreme temperature fluctuations, vibrations, and exposure to chemicals in aerospace applications.
With the use of elastomers in the construction of seals, gaskets, and dampers, these components must function properly to provide safety and reliability.
Frequently Asked Questions About Elastomers
How do elastomers differ from plastics?
Elastomers can elastically deform and return to their original shape. Most plastics cannot elastically deform and will become stiff.
Can elastomer materials function at high temperatures?
Elastomers can function at high temperatures; however, each elastomer has its own thermal limit.
Are elastomers recyclable?
Recycling of elastomers is based on polymer type and recycling facility location. Recycling is generally easier for thermoplastic elastomers than for thermoset elastomers.
Where are elastomers used the most?
Elastomer materials are most commonly found in the automotive, construction, consumer products, medical, aerospace, and industrial machinery industries for mission-critical applications.
What is the chemical resistance of elastomers?
Elastomers have different levels of chemical resistance. Nitrile and fluorosilicone elastomers are generally resistant to oils, fuels, and chemicals; however, there are a number of elastomers that are not very resistant to chemical exposure.
Conclusion: Invest in High Quality Elastomeric Materials
Elastomeric materials form the basis of numerous engineering and manufacturing innovations that we see today. The flexibility, resilience, and durability of elastomers make them a valuable material choice for a variety of applications, including automotive, aerospace, construction, medical, and consumer products. Understanding how to create and functionally use elastomers will allow professionals to see the full value and limitations of elastomers and make better selections for their individual applications.
WM F McGraw provides a large volume of comprehensive information about elastomers, composites, and polymers used in the United States. WM F McGraw is committed to assisting engineers, designers, and buyers of elastomers, composites, and polymers in making educated decisions about their choices. Our mission is to simplify the science of elastomers so professionals have confidence in their materials and make valid and practical choices.
