Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer composed exclusively of carbon and fluorine atoms. Its unique molecular structure, where each carbon atom is bonded to two fluorine atoms in a linear chain, gives it exceptional properties like chemical inertness, thermal stability, and non-stick characteristics. Commonly known as Teflon, PTFE's composition enables applications ranging from cookware coatings to industrial seals and medical devices. The material's high molecular weight and strong carbon-fluorine bonds make it resistant to extreme temperatures (-180°C to 260°C) and virtually all chemicals.
Key Points Explained:
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Basic Composition
- PTFE consists solely of carbon (C) and fluorine (F) atoms arranged in a repeating [-CF₂-CF₂-]n structure.
- The strong carbon-fluorine covalent bonds (one of the strongest in organic chemistry) provide its signature stability.
- Its high molecular weight (often millions of g/mol) contributes to its solid, dense form.
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Molecular Structure
- The fluorine atoms form a protective "shield" around the carbon backbone, preventing chemical attacks. This is why polytetrafluoroethylene resists acids, bases, and solvents.
- The symmetrical, linear chain structure results in low intermolecular forces, explaining its slippery surface and low friction coefficient (0.05–0.10).
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Key Properties Derived from Composition
- Thermal Stability: Withstands -180°C to 260°C due to the strength of C-F bonds. Melts at ~327°C but decomposes above 400°C.
- Chemical Inertness: Fluorine’s electronegativity makes PTFE unreactive to almost all chemicals, including aqua regia.
- Non-Stick Nature: The fluorine "shell" creates a smooth, hydrophobic surface that repels water and oils.
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Variants and Additives
- Virgin PTFE: Pure carbon-fluorine polymer, used where purity is critical (e.g., medical/lab equipment).
- Filled PTFE: Blended with materials like glass or graphite to improve wear resistance or reduce cold flow.
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Limitations from Composition
- Cannot be melted conventionally for molding (high melt viscosity) and must be sintered or machined.
- Prone to creep under load due to weak van der Waals forces between chains.
For purchasers, understanding PTFE’s composition clarifies its performance in extreme environments and justifies its higher cost compared to other plastics. Its inertness makes it ideal for corrosive chemical handling, while its thermal range suits both cryogenic and high-heat applications.
Summary Table:
| Aspect | Details |
|---|---|
| Basic Composition | Carbon (C) and fluorine (F) atoms in a repeating [-CF₂-CF₂-]n structure. |
| Molecular Structure | Fluorine atoms shield the carbon backbone, ensuring chemical resistance. |
| Key Properties | Thermal stability (-180°C to 260°C), chemical inertness, non-stick surface. |
| Common Applications | Industrial seals, medical devices, lab equipment, and cookware coatings. |
| Limitations | High melt viscosity, prone to creep under mechanical load. |
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