What is Elastomer?
Definition of Elastomer
An elastomer, or elastomeric polymer, is a polymeric material that exhibits rubber-like properties, characterized by a flexural modulus of less than 700 MPa according to ASTM D790 and a glass transition temperature below 25°C. It is a non-metallic, amorphous polymer that can undergo large reversible deformations under applied stress and regain its original shape upon the removal of the stress.
Molecular Structure
Elastomers are composed of long, flexible polymer chains that are lightly cross-linked, allowing them to stretch and recover their original shape. The cross-linking can be achieved through chemical bonds (thermoset elastomers) or physical interactions (thermoplastic elastomers, TPEs). TPEs consist of hard and soft segments, where the hard segments form physical cross-links, and the soft segments provide flexibility and elasticity.
Properties of Elastomer
Elastomers are polymeric materials that exhibit unique properties, including high elasticity, low modulus, and excellent reversible deformation. The key properties of elastomers are:
High Elasticity and Stretchability
Elastomers can undergo significant reversible deformation, typically up to 500-1000% elongation, without permanent set or fracture. This exceptional stretchability is attributed to their long, flexible polymer chains that can uncoil and recoil under applied stress.
Low Modulus and High Resilience
Elastomers have a low modulus of elasticity, typically in the range of 0.1–10 MPa . This low modulus allows them to deform easily under small loads, making them ideal for applications requiring flexibility and vibration damping. Additionally, elastomers exhibit high resilience, meaning they can efficiently store and release energy during deformation cycles.
Low Hysteresis and Minimal Permanent Set
Elastomers exhibit low hysteresis, which means they dissipate minimal energy during loading and unloading cycles. This property, combined with their ability to recover their original shape after deformation, results in the minimal permanent set, making them suitable for applications requiring repeated cyclic loading.
Viscoelastic Behavior
Elastomers exhibit viscoelastic behavior, meaning their mechanical properties depend on the rate and duration of applied stress. This behavior is crucial for applications involving shock absorption, vibration damping, and sealing, where the material’s response to dynamic loads is essential.
Tailorable Properties
The properties of elastomers can be tailored by modifying their chemical composition, crosslinking density, and reinforcement with fillers. This versatility allows the development of elastomeric materials with specific mechanical, thermal, and chemical resistance properties for various applications, such as tires, seals, gaskets, and biomedical devices.
Elastomers’ unique combination of properties, including high elasticity, low modulus, resilience, and tailorability, make them indispensable materials in numerous industries, including automotive, construction, aerospace, and biomedical. Their ability to withstand repeated deformation cycles while maintaining their structural integrity is crucial for various applications requiring flexibility, vibration damping, and sealing capabilities.
How is Elastomer Made?
Elastomer Composition and Raw Materials
Elastomers are typically composed of long polymer chains with cross-linking points. The main raw materials include:
- Elastomeric polymers like natural rubber, polyurethanes, polybutadiene, silicone, and neoprene
- Fillers like carbon black, silica, and fibers for reinforcement
- Vulcanizing agents like sulfur for cross-linking
- Plasticizers, oils, and processing aids
Elastomer Processing and Manufacturing
The key steps in elastomer manufacturing include:
- Compounding and mixing of raw materials using equipment like two-roll mills or internal mixers
- Vulcanization or cross-linking of the polymer chains, often using heat and pressure
- Extrusion, molding, or other shaping processes to form the final product
- Advanced techniques like dynamic vulcanization for thermoplastic elastomers
Specialty Elastomer Production
Some specialized methods are used for certain elastomer types:
- Metallocene catalysts for polyolefin elastomers
- Grafting with maleic anhydride for improved compatibility
- Ultraviolet irradiation for carbon nanotube-elastomer composites
- Foaming processes for low-density elastomeric foams
Applications of Elastomer
Elastomers have a wide range of applications due to their unique properties:
- Automotive industry: Tires, seals, gaskets, vibration isolators
- Machinery and transport: Shock and vibration damping, elastomeric bearings
- Medical devices: Prosthetics, lubricants, molds
- Textile and chemical industries
- Sports equipment, tools, airplanes
- Electronic equipment protection from impact forces
Latest Technical Innovations in Elastomer
Elastomer Compositions and Synthesis
- Novel elastomer compositions with enhanced thermal/electrical conductivity by incorporating inorganic fillers like rounded and tabular fillers. The uneven distribution of tabular fillers in the matrix improves conductivity.
- Elastomer compositions with improved moldability and sheeting properties by using a cross-linkable fluoroelastomer (A) and an ethylenically unsaturated compound (B) with a perfluoro or siloxane skeleton. The composition (B) has a minimum torque ≥0.5 kgf·cm at 60°C.
- Elastomer compositions with renewable fillers like crushed oyster shell particles (20–70 parts per 100 parts elastomer) to maintain mechanical properties while using sustainable materials.
Crosslinking and Curing
- Use of peroxide-crosslinkable fluoroelastomers and crosslinking agents in elastomer compositions for improved tensile strength, elongation, and hardness.
- Innovative curing methods like using a special silica nanoparticle mixed with silicone, followed by a specialized curing process to produce highly stretchable and strong elastomers.
Smart and Responsive Elastomers
- Development of smart elastomers with stimuli-responsive properties, such as liquid crystalline elastomers that can actuate in response to light, humidity, or electric fields.
- Healable, mechanically robust, and ultrastretchable ionic conductive elastomers for durable wearable sensors by incorporating ionic liquids or conductive fillers.
Applications and Processing
- Advances in thermoplastic elastomers (TPEs) and their alloys, enabling new applications in automotive, medical, and industrial sectors due to their processability and tunable properties.
- Improved processing techniques like cryogenic machining for elastomers, overcoming challenges in molding complex geometries.
- Development of elastomeric actuators and soft robotics applications leveraging the unique properties of elastomers.
The summary covers key innovations in elastomer compositions, crosslinking methods, smart/responsive elastomers, processing techniques, and emerging applications, drawing insights from recent patents and research papers in the field [1-20]. These advancements open up new possibilities for high-performance, sustainable, and intelligent elastomeric materials and products.
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