Elastomers are polymeric materials known for their elasticity, while synthetic fibres are engineered polymers designed for use in textiles and industry. Both play crucial roles in material science, offering distinct chemical structures and practical applications.
Elastomers
Elastomers are polymers that can undergo significant stretching and then return to their original shape when the force is removed, showing high elasticity due to their molecular structure of coiled polymer chains linked by weak intermolecular forces. A critical process is Vulcanization, which introduces chemical cross-links (e.g., sulfur bridges) between the chains. These weak, sparse links allow for reversible deformation.
Key Examples & Monomers:
- Natural Rubber (Polyisoprene): Monomer is isoprene C5H8
- Buna-S (Styrene-butadiene rubber)
- Neoprene (Polychloroprene)
- Silicone rubber
Key features:
- Low modulus of elasticity and low crystallinity
- High resilience and flexibility
- Used in tyres, seals, footwear, and engineering components
Classification of Elastomers
Elastomers are primarily classified based on their thermal behavior and the type of cross-linking:
Caption: Molecular Structure Comparison of Thermoplastic and Thermosetting Polymers
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Thermoset Elastomers (TSEs):
These are conventional rubbers with permanent, covalent chemical cross-links (formed during vulcanization). They do not melt when heated, instead degrading at high temperatures. They are not easily recyclable.
Examples: Natural Rubber (NR), Styrene-Butadiene Rubber (SBR), Ethylene Propylene Diene Monomer (EPDM), Neoprene
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Thermoplastic Elastomers (TPEs):
These have temporary physical cross-links (e.g., hard crystalline blocks) that hold the structure together at room temperature. They melt and soften when heated, allowing them to be reshaped and making them recyclable like standard plastics.
Examples: Styrenic Block Copolymers (SBS, SEBS), Thermoplastic Polyurethanes (TPU), Thermoplastic Vulcanizates (TPV), Copolyester Elastomers (COPE), Thermoplastic Polyolefins (TPO)
Applications of Elastomers
Elastomers are used where materials need to absorb shock, seal fluids, or exhibit high flexibility:
| Industry | Specific Applications | Example Elastomers |
|---|---|---|
| Automotive | Tires, Hoses (fuel/coolant), Engine and Window Seals, Vibration Dampeners. | Natural Rubber (NR), SBR, Neoprene |
| Medical | Gloves, Syringe Plungers, Surgical Tubing, Prosthetics. | Silicone, Nitrile Rubber (NBR), Latex |
| Industrial | Conveyor/Drive Belts, O-rings, Hydraulic Seals (for oil resistance), Shock Mounts. | Nitrile Rubber (NBR), EPDM, Polyurethane |
Synthetic Fibres
Synthetic fibres are man-made textiles obtained by spinning and drawing polymers into thin threads. The drawing process aligns the linear polymer chains, leading to a high degree of crystallinity and molecular orientation. This alignment maximizes strong intermolecular forces (like hydrogen bonding), resulting in their characteristic strength.
Major Types & Monomers:
- Nylon (Polyamide): Often formed via condensation polymerization (e.g., Nylon 6,6 from hexamethylenediamine and adipic acid).
- Polyester (Polyethylene terephthalate, PET): Another condensation polymer.
- Acrylic (Polyacrylonitrile)
- Rayon (Note: A regenerated cellulose fibre, not purely synthetic, but man-made.)
Important properties:
- Very high tensile strength and modulus of elasticity
- High resistance to abrasion, chemicals, and moisture
- Used in clothing, ropes, carpets, and high-performance industrial fabrics
Applications of Synthetic Fibres
Synthetic fibres are used for their high strength, durability, and resistance to environmental factors:
| Fibre Type | Key Properties Used | Specific Applications |
|---|---|---|
| Polyester | Wrinkle resistance, durability, quick-drying. | Apparel (shirts, fleece), Home furnishings, Industrial reinforcements (tire cords, belts). |
| Nylon | Extreme strength, high abrasion resistance, lightweight. | Ropes (climbing/marine), Parachutes, Seatbelts, Carpets, Hosiery. |
| Spandex (Lycra) | Exceptional stretch (500%) and elastic recovery. | Activewear, Swimwear, Underwear (blended with other fibres). |
| Aramid (Kevlar/Nomex) | Very high tensile strength, heat/flame resistance. | Protective clothing, Ballistic body armor, Aerospace composites. |
Comparison of Elastomers and Synthetic Fibres
| Property | Elastomers | Synthetic Fibres |
|---|---|---|
| Structure | Coiled, Amorphous, Low Crystallinity | Linear, Highly Oriented, High Crystallinity |
| Intermolecular Forces | Weak van der Waals forces | Strong (e.g., Hydrogen bonding, Dipole-Dipole) |
| Cross-linking | Present (essential for elastic recovery) | Generally absent (or minimal) |
| Elasticity / Strength | High elasticity, Low tensile strength | Moderate elasticity, Very High tensile strength |
| Examples | Rubber, Neoprene | Nylon, Polyester, Acrylic |