PTFE (Polytetrafluoroethylene) labware is renowned for its exceptional chemical resistance, making it a preferred choice in laboratories handling aggressive substances. It withstands nearly all acids, alkalis, and solvents, maintaining stability up to its maximum operating temperature of 500°F (260°C). However, it is vulnerable to molten alkali metals, fluorine, chlorine trifluoride, and certain fluorochemicals under high temperatures or pressures. Its hydrophobic nature, low friction coefficient, and thermal stability further enhance its suitability for applications requiring non-reactivity and durability.
Key Points Explained:
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Broad Chemical Resistance
- PTFE is chemically inert to most laboratory chemicals, including:
- Concentrated acids (e.g., sulfuric, nitric, hydrochloric)
- Strong bases (e.g., sodium hydroxide)
- Organic solvents (e.g., acetone, ethanol, toluene)
- This inertness stems from its strong carbon-fluorine bonds, which resist bond-breaking by reactive substances.
- PTFE is chemically inert to most laboratory chemicals, including:
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Exceptions and Vulnerabilities
PTFE degrades under specific conditions:- Molten alkali metals (e.g., sodium, potassium): These react aggressively with PTFE’s fluorine atoms.
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Fluorine and fluorochemicals:
- Gaseous or turbulent fluorine at high temperatures/pressures.
- Chlorine trifluoride (ClF₃) and oxygen difluoride (OF₂), which release free fluorine.
- These exceptions occur because fluorine-based compounds can break PTFE’s C-F bonds under extreme conditions.
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Temperature Limitations
- PTFE remains stable up to 260°C (500°F) continuously.
- Above this threshold, thermal decomposition begins, reducing chemical resistance.
- Short-term exposure to higher temperatures (e.g., 327°C melting point) is possible but risks material softening.
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Additional Properties Enhancing Utility
- Hydrophobicity: Repels water, preventing moisture-related contamination.
- Non-stick surface: Minimizes residue buildup, simplifying cleaning.
- Low friction: Ideal for stirrers, seals, and tubing where smooth motion is critical.
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Applications in Labware
PTFE’s resistance makes it suitable for:- Reaction vessels, tubing, and stir bars in corrosive environments.
- Linings for autoclaves or containers storing aggressive chemicals.
- Seals and gaskets in high-purity systems (e.g., semiconductor manufacturing).
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Considerations for Purchasers
- Verify compatibility with specific chemicals (e.g., halogenated compounds).
- Assess temperature requirements; alternatives like PFA may be needed for higher heat.
- Prioritize PTFE’s non-reactive nature for trace analysis to avoid contamination.
PTFE’s near-universal resistance, combined with its thermal stability, underscores its role as a cornerstone material in laboratories. However, understanding its limitations ensures safe and effective use in specialized applications.
Summary Table:
| Property | Details |
|---|---|
| Chemical Resistance | Resistant to nearly all acids, alkalis, and organic solvents. |
| Exceptions | Vulnerable to molten alkali metals, fluorine, and certain fluorochemicals. |
| Temperature Limit | Stable up to 260°C (500°F); decomposes at higher temperatures. |
| Key Features | Hydrophobic, non-stick, low friction, and thermally stable. |
| Common Applications | Reaction vessels, tubing, seals, and linings for corrosive environments. |
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