Since the 1938 invention of PTFE, its integration into valve seats has revolutionized chemical resistance standards – yet traditional rubber seats still dominate 58% of water treatment applications (Fluid Controls Institute). material selection for butterfly valve seats has become a critical factor in operational efficiency. While PTFE and rubber remain the top contenders, their distinct properties – from chemical resistance to lifecycle costs – demand rigorous analysis. This article contrasting PTFE’s space-age capabilities with rubber’s cost-effective versatility in modern butterfly valves. Empowering engineers to make data-backed decisions.
1.In terms of chemical properties
PTFE is an excellent chemical material that is resistant to almost all strong acids (such as concentrated sulfuric acid, hydrochloric acid), strong bases, organic solvents, and oxidants (such as chlorine gas).
RubberEPDM/NBR Compared to PTFE, ordinary rubber is slightly inferior. It is resistant to weak acids and alkalis and suitable for media such as water and steam, but it is prone to swelling in oil or hydrocarbon media.
2.Temperature Tolerance
The PTFE-coated butterfly valve plate demonstrates outstanding performance within a temperature range of -200°C to 200°C, making it particularly suitable for handling corrosive, viscous, or high-purity media.
For applications approaching 260°C, Long-term thermal aging must be evaluated, as PTFE may gradually degrade under sustained high temperatures.
If the temperature exceeds 260°C, PTFE will undergo softening and deformation, compromising sealing integrity. To mitigate this, the following strategies can be employed:
Reinforced valve plate design (e.g., thicker PTFE lining or metal backing)
Filled PTFE composites (e.g., glass fiber/carbon-filled) to enhance creep resistance.
For common rubber materials, taking EPDM and NBR as representative examples:
EPDM (Ethylene Propylene Diene Monomer):
Continuous service temperature: -40°C to +120°C
Short-term peak tolerance: Up to +150°C
NBR (Nitrile Butadiene Rubber):
Continuous service temperature: -20°C to +80°C
Short-term peak tolerance: Up to +100°C
3.Mechanical Strength
PTFE (Polytetrafluoroethylene)
Creep Resistance: Low-prone to deformation under sustained load
Structural Requirement: Typically requires metal reinforcement (e.g., embedded backing plate) to prevent cold flow
Long-Term Stability: Not ideal for high-stress static sealing applications
Rubber (EPDM/NBR/FKM, etc.)
Elastic Recovery: Excellent-quickly regains original shape after compression
Compression Set Resistance: High – minimal permanent deformation under prolonged load
Dynamic Performance: Well-suited for applications with frequent movement or vibration
4.Environmental Impact
PTFE (polytetrafluoroethylene)
Production stage: The manufacturing process requires the use of PFAS substances such as perfluorooctanoic acid (PFOA), and due to the sintering temperature of PTFE material being greater than 360 , it is a high energy consuming process. In terms of waste disposal: it naturally decomposes for hundreds of years, is difficult to degrade, and high-temperature incineration may produce toxic gases such as hydrofluoric acid. The recycling technology is complex and requires professional chemical decomposition.
Ordinary rubber (EPDM/NBR, etc.)
Production stage: The raw materials for rubber are petroleum derivatives, which have high carbon emissions. During the vulcanization process, sulfides are released, requiring exhaust gas treatment. When disposing of waste, it can be physically recycled, such as crushing rubber materials and using them for low-end products, which can be recycled and reused; Energy can be recovered through thermal cracking, and rubber has better natural degradability than PTFE.
5.Installation and Maintenance Comparison
PTFE seals
Higher installation accuracy is required:
During installation, the valve plate and valve seat need to be accurately aligned to avoid deformation due to uneven pressure (cold flow). If necessary, anti-corrosion treated metal reinforcements (such as 316L stainless steel sleeves) can be added
Maintenance free advantages:
PTFE material is self-lubricating and does not require additional lubricants. It has chemical inertness and excellent aging resistance (usually can operate for more than 10 years without maintenance)
Rubber seal
Compared to PTFE material seals, ordinary rubber is easier to install because the rubber elasticity compensates for slight misalignment (allowing for ± 5% axial deviation) and can be trimmed or adjusted on site (such as O-rings)
More frequent maintenance:
Regular lubrication is required (silicone grease can extend service life), and seals need to be replaced every 2-3 years (can be used for dynamic sealing applications)
6.Cost Analysis
PTFE: High initial cost (3-5 times that of rubber), ultra-low friction coefficient (0.05-0.1), self-lubricating properties, suitable for high-frequency switch operation, long service life (up to 10 years in chemical environments).
Rubber: relies on lubricants, has a high coefficient of friction (0.3-0.6), and is prone to wear. It is an economical choice, but it requires frequent replacement (2-3 years of maintenance).
7.Regulatory Compliance
PTFE (Including Modified Materials like RPTFE)
Perfluorinated Compound Restrictions
EU REACH Regulation: Limits PFOA (perfluorooctanoic acid) content to <25 ppb (Annex XVII)
U.S. EPA: PFAS substance emission reporting requirements (TSCA Section 8(a)(7))
Food/Pharmaceutical Contact
FDA 21 CFR 177.1550: Migration testing standards for food-grade PTFE
EU 10/2011: Compliance for plastic food contact materials
Industrial Safety
OSHA 29 CFR 1910.1200: GHS labeling requirements (inhalation risk of dust)
China GB/T 33061-2016: Standards for fluoropolymer waste disposal
Conventional Rubber (EPDM/NBR/FKM, etc.)
Hazardous Substance Control
EU RoHS 2.0: Restricts phthalates (e.g., DEHP <0.1%)
California Proposition 65: Warning labels for nitrosamine carcinogens
Food/Medical Compliance
FDA 21 CFR 177.2600: Standards for rubber food contact materials
USP Class VI: Biocompatibility certification for medical rubber
Environmental Requirements
EU ELV Directive: Recyclability rate of automotive rubber ≥85%
China GB 24429-2009: Limits on polycyclic aromatic hydrocarbons (PAHs) in rubber products
8.Industrial Application
PTFE (polytetrafluoroethylene) seals
Typical application scenarios include chemical/petrochemical industries, such as strong acid and alkali pipelines and chlor alkali industries; High purity industries, such as semiconductor ultrapure water systems and pharmaceutical GMP clean pipelines; In the energy sector, such as LNG low-temperature valves (-196 ° C operating conditions) and high-temperature flue gas baffles (≤ 260 ° C) in thermal power plants; Special operating conditions, such as high-frequency opening and closing control valves (>100000 times/year) and vacuum seals (aerospace components).
Ordinary rubber (EPDM/NBR/FKM) seals
Typical application scenarios include general industry, such as water/sewage treatment and HVAC water systems; Fluid transportation, such as oil pipelines and food grade pipelines (FDA certified EPDM); Mobile equipment, such as car cooling systems and hydraulic cylinder seals; Quick repair scenarios, such as pipeline expansion joints and pump inlet and outlet soft connections.
Conclusion: Strategic Material Selection in Valve Engineering
The PTFE vs. rubber debate in butterfly valve seat design ultimately resolves into a multidimensional optimization challenge. While PTFE excels in aggressive chemical environments (-20°C to 260°C operational range) and offers superior FDA compliance for sensitive industries, natural/synthetic rubber variants maintain dominance in low-pressure vibration damping applications through their unique elastic memory.
Lifecycle Carbon Footprint: NBR rubber's biodegradability vs. PTFE's 50+ year service durability.
Smart Manufacturing Synergy: PTFE's compatibility with automated installation systems.
Regulatory Evolution: REACH SVHC updates impacting synthetic rubber formulations.
Recent advancements like carbon-filled PTFE (30% enhanced compressive strength) and peroxide-cured EPDM (extended UV resistance) demonstrate material science's dynamic progression. For optimal selection, implement a decision matrix prioritizing:
Life cycle carbon footprint: The biodegradability of NBR rubber and the over 50+ year lifespan of PTFE.
Intelligent Manufacturing Collaboration: Compatibility between PTFE and Automated Installation Systems.
Regulatory Evolution: REACH SVHC Update Affects Synthetic Rubber Formulations.
The latest developments in materials science include carbon filled PTFE (with a 30% increase in compressive strength) and peroxide cured EPDM (with enhanced UV resistance). To achieve the best choice, implement a decision matrix that prioritizes:
1. The main characteristics of the medium, such as pH value, i.e. acidity or alkalinity, and the presence of abrasives.
The calculation of total cost must include the downtime for seat replacement.
3. Does it comply with industry certification standards such as API 609 and EN 593.
