PTFE Gasket Chemical Resistance Guide With Detailed Compatibility Chart

Polytetrafluoroethylene (PTFE) gaskets are renowned in industrial applications for their exceptional chemical resistance, making them a go-to choice for sealing in harsh environments.

Understanding the chemical resistance of PTFE gaskets is crucial for ensuring safety, longevity, and performance, whether you’re dealing with aggressive acids, solvents, or bases.

This comprehensive guide explores the properties of PTFE, key factors influencing its compatibility, and provides a detailed PTFE chemical compatibility chart compiled from reliable sources.

What is PTFE and Why Use It in Gaskets?

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer discovered in 1938 by DuPont chemist Roy Plunkett. Commonly known by the brand name Teflon, it’s composed of carbon and fluorine atoms, forming a strong, inert molecular structure that resists breakdown from most chemicals.

Due to the combination of properties like chemical inertness, temperature resistance, and non-contaminating properties, like high-performance PTFE sealing. PTFE gaskets are widely used in industries like chemical processing, pharmaceuticals, food and beverage, and oil and gas due to their unique properties.

To understand their complete structure and performance, you can explore PTFE gaskets and their properties.

Key Advantages of PTFE Gaskets Include:

1. High Chemical Inertness: PTFE resists attack from nearly all chemicals, excluding a few like molten alkali metals and fluorine gas under extreme conditions.

2. Temperature Tolerance: Due to its wide range of temperature tolerance, it is suitable for both cryogenic and high-heat applications.

3. FDA Compliance: Due to the combination of properties like chemical resistance, chemical inertness, temperature resistance, and non-contaminating properties. Virgin PTFE is approved for food contact, ideal for hygienic applications.

4. Non-Stick Surface: Prevents adhesion of residues, easing maintenance, thus the best suitable in the food industry.

5. Low Friction: PTFE has one of the lowest coefficients of friction among solids, reducing wear in dynamic sealing.

6. Excellent electrical insulation: thus, the best in semiconductor manufacturing.

7. Long service life: Low degradation, low maintenance.

8. UV & weather resistance: due to its high resistance towards UV rays received with sunlight, it is suitable for outdoor chemical environments.

Understanding PTFE Chemical Resistance

PTFE’s chemical resistance comes from its strong carbon-fluorine bonds, which is the most stable in organic chemistry.

Fluorine atoms shield the carbon chain, preventing reactions with electrophiles or nucleophiles.

This makes PTFE impervious to most acids (e.g., sulfuric, nitric), bases (e.g., sodium hydroxide), organic solvents (e.g., acetone, benzene), and oxidizers.

General Compatibility Rules for PTFE Gasket

1. Acids: PTFE shows excellent resistance to strong acids like hydrochloric (HCl) and sulfuric (H2SO4) at concentrations up to 100% and temperatures up to 212°F.

2. Bases: Compatible with alkalis like ammonia and sodium hydroxide, though prolonged exposure to molten alkalis can cause issues.

3. Solvents: Resists alcohols, ketones, and hydrocarbons without swelling or dissolving.

4. Oxidisers: Handles hydrogen peroxide and chlorine well, but fluorine and certain halogenated compounds at high temperatures may react.

If you’re comparing PTFE with alternative sealing materials, review our PTFE vs rubber gaskets comparison.

Exceptions and Limitations of PTFE Gasket

1. Molten Alkali Metals: Sodium or potassium in liquid form can defluorinate PTFE.

2. Fluorine Gas: Reacts violently, forming tetrafluoromethane.

3. High-Pressure Halogens: Chlorine trifluoride or bromine trifluoride may degrade it.

4. Radiation: While chemically resistant, PTFE can be affected by high radiation doses, leading to embrittlement.

Why Chemical Resistance Matters in Gaskets

Piping systems and industrial equipment often handle highly corrosive chemicals. If the gasket material is incompatible, it may lead to:

• Unexpected downtime and costly repairs
• Contamination of products
• Swelling, cracking, or softening of the gasket
• Leakage and failure of sealing joints
• Safety risks for workers

Types of PTFE Gaskets with Their Chemical Compatibility

PTFE gaskets are of multiple variations, each designed with specific industrial requirements:

1. Virgin PTFE Gaskets

   Best chemical resistance, made from 100% pure PTFE, Suitable for food, pharma, and ultra-pure applications.

2. Filled PTFE Gaskets

   PTFE is blended with fillers to improve specific properties:

   • Glass-filled PTFE – improved wear resistance
   • Carbon-filled PTFE – enhanced compressive strength
   • Graphite-filled PTFE – better heat conduction
   • Bronze-filled PTFE – high mechanical stability

   Although filled PTFE enhances mechanical performance, its chemical resistance slightly reduces compared to virgin PTFE.

3. Expanded PTFE (ePTFE) Gaskets

   Flexible, Ideal for irregular surfaces, Excellent sealing performance under low bolt loads.

   Each type has excellent resistance to most chemicals, but virgin PTFE is the most universally compatible.

PTFE Gasket Chemical Resistance Chart

Factors Affecting PTFE Gasket Chemical Compatibility- While PTFE is highly resistant, several variables influence its performance.

Temperature	Resistance decreases at extremes. For example, sulfuric acid is compatible up to 212°F, but fuming oleum may cause issues above that.
Concentration	Dilute solutions are generally safer than concentrated ones. Hydrofluoric acid (HF) at 40% is resistant, but anhydrous HF requires caution.
Pressure	High pressure can force permeation, especially with gases like hydrogen.
Exposure Duration	Short-term contact is fine for most chemicals, but long-term immersion may lead to minor absorption in solvents.
Gasket Type	Virgin PTFE is purest for chemicals; filled versions (e.g., glass-filled) may have slightly altered resistance but improved compressive strength.
Mechanical Stress	Compression set or creep can occur under load, indirectly affecting seal integrity.

PTFE Gasket Chemical Compatibility Chart

Below is a detailed compatibility chart covering the most commonly used industrial chemicals.

Rating	Meaning
A	Excellent – Recommended (no attack, long service life)
B	Good – Minor effect (generally acceptable)
C	Fair – Use with caution (may require filled PTFE or special grade)
D	Not recommended (high attack, risk of failure)

Chemical Compatibility Chart for PTFE Gaskets

Acids

Chemical	Concentration	Rating	Notes
Hydrochloric Acid	ALL	A	Fully resistant
Sulfuric Acid	0-70%	A	Safe at moderate temperatures
Sulfuric Acid	70-98%	B	Acceptable with caution
Nitric Acid	≤ 70%	B	Slow reaction at very high temperatures
Nitric Acid	> 70%	C	Consider special PTFE grades
Acetic Acid	ALL	A	Completely compatible
Hydrofluoric Acid	ALL	A	No degradation
Phosphoric Acid	ALL	A	Safe in most applications
Chromic Acid	ALL	C	Strong oxidizer—use caution.

Alkalis

Chemicals	Concentration	Ratings	Notes
Sodium Hydroxide	All	A	Excellent compatibility
Potassium Hydroxide	ALL	A	No reaction
Ammonia (liquid)	ALL	A	Very stable

Solvents

Chemicals	Rating	Notes
Acetone	A	No absorption or swelling
Benzene	A	Excellent resistance
Toluene	A	No attack
Methanol	A	Safe for long-term exposure
Ethanol	A	No effect
Ether	A	Completely compatible
Chloroform	A	Highly resistant
Carbon Tetrachloride	A	No observable effect

Oils & Hydrocarbons

Chemicals	Rating	Notes
Diesel	A	Ideal sealing
Gasoline	A	No reaction
Mineral Oils	A	Fully compatible
Motor Oil	A	Excellent resistance

Gases

Chemicals	Rating	Notes
Chlorine (dry)	A	Stable
Chlorine (wet)	B	Slightly more reactive
Hydrogen	A	No attack
Oxygen	A	Completely inert

Applications of PTFE Gaskets in Chemical-Intensive Industries

Due to their universal compatibility, PTFE gaskets are widely used in:

1. Chemical Processing Plants- due to their aggressive chemical resistivity, PTFE are used as a Sealing reactors, handling acids or solvents, Pumps, reactors, heat exchangers, storage tanks, and pipelines

2. Pharmaceutical & Biotech- due to its advanced chemical reactive nature it maintains the required purity while manufacturing life-saving drugs and pharma products, along with other functions like Sterile fluid transfer, high-purity applications, CIP/SIP systems

3. Food & Beverage- because of properties like non-sticky and non-adhesive nature, FDA-approved PTFE is used in hygienic process lines.

4. Petrochemical & Refineries- due to its high temperature and pressure resistivity it is most suitable for Hydrocarbon processing, oil & gas piping systems

5. Water & Wastewater Treatment- due to PTFE’s ability to withstand high temperature it is Suitable for corrosive chemical dosing (chlorine, sulfuric acid, caustic soda), handles chlorines and ozonated water.

6. Pulp & Paper- Used in bleach plants and chemical washers

7. Semiconductor Manufacturing- because of being a good conductor of electricity, Ultra-pure, non-contaminating properties, they are used in manufacturing electrical appliances

Limitations of PTFE Gaskets

Even though PTFE is highly durable, it does have a few limitations. Knowing these limitations helps in selecting the right type of PTFE gasket:

• Cold flow (creep) under high bolt loads
• Reduce mechanical strength compared to graphite or metal gaskets
• Filled PTFE may be needed for high-pressure applications
• Not suited for molten alkali metals or highly reactive fluorine compounds

Maintenance and Best Practices for PTFE Gaskets

Regular audits ensure compliance with standards like ASME B16.21.

To maximise lifespan:

• Timely inspections- make sure to inspect for creep (permanent deformation) after installation.
• Torque- Use torque specifications to avoid over-compression.
• Storage- Store in cool, dry places away from ozone.
• Follow the Replacement guide- Replace if exposed to incompatible chemicals like fluorine.

Conclusion

PTFE gaskets have one of the broadest chemical resistance profiles. Thus making them one among the first choices for sealing applications in different industries like pharmaceutical, petrochemical, waste water treatment, chemical, and even in food and beverages.

If you’re looking for a reliable sealing solution, check our PTFE gasket product range for all applications.

Their ability to tolerate a wide range of strong acids, solvents, and oxidisers, along with an extreme temperature range, ensures their efficiency, safety, and longer service life.

Also, by going through the PTFE gasket chemical compatibility chart provided in this guide, one can easily make the right gasket selection, thus eventually reducing the downtime, hassle and reliability of the overall system.

FAQs (Frequently Asked Questions)