Basic definition:
The first elastomer to exist was rubber. It comes from the Indian word ” cahutchu “, meaning “weeping wood”.
Elastomers are polymers of natural or synthetic origin with elastic properties, meaning that they can deform considerably under stress, but return to their initial shape once the stress is released. Unlike conventional plastics, which are generally stiffer, elastomers are highly elastic and have excellent shock and vibration absorption properties.
Molecular structure :
The molecular structure of elastomers consists of flexible polymer chains interwoven with one another. This unique configuration enables elastomers to deform and fold reversibly under stress, then return to their original shape once the stress is released. This gives them their distinctive elasticity.
Elastomer types :
There are several types of elastomer, each with specific properties tailored to particular applications. The most common synthetic elastomers include silicone rubber, nitrile rubber, chloroprene rubber and fluorelastomer rubber. Each of these materials offers unique characteristics such as chemical resistance, resistance to extreme temperatures and durability, … making them suitable for diverse applications ranging from seals, sporting goods, to medical products. Some elastomers are designed for :
- high abrasion resistance (as per DIN ISO 4649-A)
- cut-resistant (ideal for the manufacture of conveyor chains, for example)
- be compatible with food contact
- benefit from a toy standard
- be fireproof
- be used in the medical field
There are 2 main categories of elastomer:
- Thermoplastic elastomers
- Thermoset elastomers
THERMOPLASTIC ELASTOMERS
All TPEs are composed of hard and soft segments.
Thermoplastic elastomers can be :
- Copolymers
- Terpolymers
Physical polymer blends (usually plastic and rubber) made from materials with both thermoplastic and elastomeric properties.
Thermoplastics can be recycled and do not require cross-linking or vulcanization like thermoset elastomers.
THERMOSET ELASTOMERS
It is obtained by cross-linking two components, which react under the action of heat in the presence of reagents (catalyst and polymerization gas pedal).
The three-dimensional structure (network) formed is stable and offers higher thermomechanical and chemical resistance than thermoplastics.
The transformation of a thermosetting elastomer is irreversible: it becomes infusible and non-recyclable.
Manufacturing and applications :
Elastomers are manufactured using polymerization processes similar to those for other polymers, but they generally undergo a vulcanization stage to improve their physical properties. Once formed, elastomers are used in a multitude of applications:
- Automotive industry: door seals, interior parts, wiring
- Construction and industry: sealing parts, piping, tools, protective equipment
- Hoses and fluid transport: seals, shower hoses,
- Electricity: cable sheathing, charging cables,
- Consumer goods: household appliances, toothbrushes, utensil handles, etc.
- Sport and leisure: shoe soles, sports and wellness equipment,
- Packaging and protection: flexible smartphone shells, flexible protective parts, elastic parts, …
Elastomer processing
- Thermosetting elastomer processing :
- Cold mixing and homogenization (approx. 30°C)
- Injection/extrusion/compression, …
- Curing by baking (approx. 170°C, 10 min)
- Thermoplastic elastomer processing :
- Heating and mixing (plastification)
- Injection/extrusion
- Cooling.
Hardness ranges
Elastomers are initially characterized by their surface hardness, which can be measured by various methods (Shore, Vickers (HV), Brinell (HB), Rockwell (HR), etc.).
The most commonly used is Shore hardness, which is based mainly on 2 scales: Shore A and Shore D.
Benefits and significance :
Elastomers offer a unique combination of flexibility, resilience and durability, making them valuable materials in many industries. Their ability to absorb shock and vibration makes them essential in applications where safety and reliability are paramount, while their adaptability makes them versatile materials for a diverse range of products and components.
Conclusion:
Elastomers play an essential role in our daily lives and in many industries. Whether for automotive products, medical equipment or industrial applications, elastomers will continue to play a vital role in our modern, dynamic world.
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