| HS Code | 877125 |
| Chemical Name | Perfluorosulfonic acid resin |
| Cas Number | 66796-30-7 |
| Appearance | Transparent or translucent white pellets, film, or dispersion |
| Density | 1.9 - 2.1 g/cm³ |
| Equivalent Weight | 800 - 1200 g/mol SO3H (typical 1100) |
| Ionic Conductivity | Up to 0.1 S/cm when fully hydrated |
| Water Uptake | 20 - 40 wt% depending on temperature and equivalent weight |
| Chemical Resistance | Excellent resistance to strong acids, bases, and oxidizing agents |
| Thermal Stability | Stable up to 200°C; onset of decomposition above 280°C |
| Mechanical Tensile Strength | Approximately 20 - 40 MPa depending on hydration and form |
| Glass Transition Temperature | Approximately 110 - 130°C in dry form |
| Solubility | Insoluble in water but dissolves in some polar solvents such as water-alcohol mixtures at elevated temperature |
As an accredited Perfluorosulfonic Acid Resin factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Perfluorosulfonic Acid Resin is packaged in sealed polyethylene bags inside fiber drums, typically 5 kg net weight, protected from moisture. |
| Container Loading (20′ FCL) | 20′ FCL: Perfluorosulfonic Acid Resin loaded in sealed drums on pallets, securely lash-braced, container doors sealed for transport. |
| Shipping | Perfluorosulfonic Acid Resin ships as a non-hazardous solid, typically in sealed, moisture-resistant containers. Protect from humidity and direct sunlight. Standard dry freight is suitable; avoid extreme temperatures. Ensure proper labeling and documentation for customs, and follow standard handling procedures to prevent dust inhalation and contamination. |
| Storage | Store Perfluorosulfonic Acid Resin in a cool, dry, well-ventilated area, away from heat, ignition sources, and incompatible substances. Keep containers tightly sealed to prevent moisture absorption and contamination. Avoid direct sunlight and store in original labeled packaging. Use secondary containment for spill control, and handle with appropriate PPE including gloves and eye protection. |
| Shelf Life | Perfluorosulfonic acid resin has a typical shelf life of 2–5 years when stored cool, dry, and tightly sealed. |
In membrane chlor-alkali electrolysis, perfluorosulfonic acid resin is not used as a free powder but is converted into a laminated cationic barrier comprising a sulfonic acid bulk transport layer, a thinner carboxylic acid anion-rejection layer, and a polytetrafluoroethylene woven reinforcement. The sulfonic acid layer typically carries an ion exchange capacity of 0.8–1.0 meq/g, while the carboxylic acid layer is formulated with a lower capacity, commonly 0.5–0.8 meq/g, to suppress hydroxyl back-migration without increasing cell voltage beyond acceptable limits. A slot-die coater deposits an aqueous/alcoholic dispersion containing 20–40 wt% PFSA solids onto a release film; drying is staged from 60°C to 120°C to avoid skin-over and blistering, and beta-gauge scanners hold dry thickness tolerance to ±2 µm. The dried layers are laminated to the PTFE fabric at 180–230°C and 1–3 MPa for 30–60 s, after which the membrane is hydrolysed in 10–15 wt% NaOH at 50–80°C and exchanged to the acid form. In commercial cells the membrane operates at 85–90°C, a current density of 4–6 kA/m², and a catholyte strength of 30–33 wt% NaOH. To avoid precipitation of calcium and magnesium hydroxides at the membrane surface, combined brine hardness is generally held below 0.05 mg/L. Caustic current efficiency typically remains above 95%, while oxygen in chlorine gas after drying is specified below 0.5 vol% in most plant quality control specifications. The terminal outputs are 32 wt% aqueous sodium hydroxide, chlorine gas that is compressed and liquefied after drying, and hydrogen that may be vented or compressed for on-site use.
Because proton conductivity is governed by equivalent weight, water uptake, and dispersant selection, thin cast PFSA fuel cell membranes require exacting dispersion control and thermal annealing. For cathode catalyst ink, the ionomer-to-carbon weight ratio is typically 0.65–0.85 for platinum-on-carbon catalysts with 20–40 wt% Pt; the solvent is a 1:1 by mass mixture of water and 1-propanol, and the final ink is diluted to 1–5 wt% solids before slot-die or gravure coating onto a polytetrafluoroethylene release carrier. Membrane layers of 10–50 µm dry thickness are cast and dried from 25°C to 80°C, then annealed at 140–160°C for 1–2 h to develop crystallinity and reduce hydrogen crossover. Catalyst-coated membranes are formed by hot pressing decals at 140–160°C and 2–4 MPa for 2–5 min, followed by proton exchange in 0.5 M H₂SO₄ at 60°C for 1 h and rinsing until wash water pH exceeds 6.5. Hydrated conductivity at 80°C and 95% RH is commonly 0.08–0.12 S/cm; hydrogen crossover is specified below 1.5 mA/cm² at 100 kPa differential pressure. Mechanical acceptance is based on ASTM D638-14 tensile strength of 20–30 MPa and elongation of 150–250% at 23°C and 50% RH. For stationary stacks, IEC 62282-3-100 safety requirements apply, while module performance is evaluated under IEC 62282-3-200; membrane mechanical durability is screened under DOE-derived wet/dry cycling protocols at 80°C with humidity cycling between 100% RH and 0% RH. The terminal product is a proton exchange membrane fuel cell stack rated from 1 kW to more than 200 kW, used in vehicles, stationary backup power, and material handling.
At current densities above 1.0 A/cm², PFSA membranes for PEM water electrolysis are selected primarily for differential pressure tolerance and low ionic resistance. Reinforced membranes of 100–250 µm thickness contain 60–80 mass% PFSA and 20–40 mass% ePTFE or a chemically stabilised polyaryl sulfone mesh; this construction keeps ionic resistance below 0.10 Ω·cm² at 80°C in deionised water. Anode catalyst layers typically use iridium oxide at 1.5–2.5 mg/cm² with an ionomer-to-catalyst ratio of 0.4–0.6, while cathode layers use platinum-on-carbon at 0.3–0.5 mg/cm². Catalyst-coated membranes are laminated at 130–150°C and 1.5–2.5 MPa for 90–180 s, then boiled in 0.5 M H₂SO₄ for 1 h and rinsed until rinse-water conductivity is below 1 µS/cm. The operating window is 50–80°C, 20–50 bar differential pressure, and 1.0–2.0 A/cm²; cell voltage at 2.0 A/cm² and 80°C is typically 1.8–2.0 V. Hydrogen product quality must satisfy ISO 14687 at the system outlet; pressurised components fall under the Pressure Equipment Directive 2014/68/EU, and the hydrogen generator system is assessed under ISO 22734. Generated hydrogen is dried and purified to 99.999 volume% before delivery. Tensile strength of reinforced membrane per ASTM D638-14 is specified above 30 MPa to resist creep under differential pressure. The terminal product is compressed hydrogen for industrial processes, refuelling, or gas grid injection.
Vanadium redox flow battery stacks use perfluorosulfonic acid membranes as a proton-conducting separator, not as an electrode binder. The membrane is normally selected from equivalent weights between 800 g/mol and 1100 g/mol and is cast at 50–125 µm dry thickness, often onto expanded PTFE reinforcement to reduce in-plane swelling. After solution casting, the film is annealed at 150–180°C for 1–3 h, then exchanged in 1 M H₂SO₄ at 25°C for 24 h to remove solvent and displace sulfonyl fluoride residues. Area-specific resistance measured by electrochemical impedance spectroscopy in 1 M H₂SO₄ at 25°C falls between 0.05 Ω·cm² and 0.15 Ω·cm²; vanadium permeability is typically below 20 × 10⁻⁷ cm²/min at 25°C. In stack service, coulombic efficiency of 95–98% and energy efficiency of 80–85% are achieved at current densities of 80–120 mA/cm², with voltage efficiency between 85% and 90%. The electrolyte is a mixed vanadium sulfate solution in 2–3 M H₂SO₄; long-term exposure above 40°C accelerates membrane oxidation by pentavalent vanadium, so stack cooling is required above 40°C. Compliance for stationary systems is assessed under IEC 62932-2-1, with additional fire and leak testing per local electrical codes. The terminal product is a containerised energy storage system covering 100 kW to 100 MW, used for renewable firming and grid frequency regulation.
In fixed-bed esterification reactors, PFSA resin is supplied as a pelleted or extruded solid superacid with a Hammett acidity approximately -12, an acid capacity of 0.8–1.0 meq/g, and a thermal stability limit near 150°C for continuous operation. The resin is loaded as 0.2–1.0 mm beads into a tubular column with length-to-diameter ratio 10:1; the reactor is fed a methanol-to-acetic acid molar ratio between 1.5:1 and 3.0:1 at liquid hourly space velocity 0.5–2.0 h⁻¹. Temperature is held at 60–120°C and pressure at 0.1–2.0 MPa to keep the alcohol in the liquid phase. Catalytic activity declines when water content exceeds 10 wt% in the feed, because the sulfonic acid sites hydrate and lose acid strength; in commercial practice a pervaporation or extractive drying loop maintains water below 5 wt%. Regeneration is performed in situ with 10 wt% H₂SO₄ at 60°C for 2–4 h after loss-on-activity exceeds 20%. Amine-based inhibitors quench sulfonic acid sites and are excluded from the reactor feed. The resin is not registered as hazardous under CLP Regulation 1272/2008, but EU REACH Regulation 1907/2006 registration applies to the sulfonyl fluoride precursor imported for manufacturing. Terminal products include methyl acetate, ethyl acetate, and other ester solvents with residual acid catalyst below 0.1 wt% after distillation.
For solid-contact CO sensors, perfluorosulfonic acid ionomer is deposited between the sensing and counter electrodes of amperometric gas sensors as a 1–10 µm cast film from a 5 wt% dispersion in water/1-propanol. The electrode paste uses Pt/C at 0.1–0.5 mg/cm²; the ionomer-to-carbon ratio in the electrode is adjusted to 0.3–0.7 because excess ionomer blocks gas diffusion and reduces sensitivity. After casting, sensors are dried at 25°C and 50% RH for 12–24 h and preconditioned at 0.6 V versus a Pt pseudo reference for 2 h in humidified air. Baseline current in this configuration is typically 10–100 nA at 25°C; CO sensitivity is 50–500 nA/ppm and T90 response time is below 30 s. Below 30% RH, proton conductivity falls sharply and the baseline shifts, which mandates internal humidity buffering or a printed hygroscopic layer. Contact with ammonia or volatile amines must be excluded because these species neutralise the sulfonic acid sites on the PFSA ionomer and cause irreversible sensitivity loss. For toxic gas response, sensors are validated under EN 45544-1 and EN 45544-2 for CO, and portable instruments are assessed under IEC 60079-29-1 for combustible gas detectors where applicable. The terminal product is a diffusion-limited amperometric gas detector used in enclosed workplace and underground parking atmospheres.
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Perfluorosulfonic acid resin is a perfluorinated copolymer built from a tetrafluoroethylene backbone and pendant perfluorovinyl ether side chains terminated with sulfonic acid groups. The resin is supplied as free-flowing powder, pellet, or aqueous-alcoholic dispersion under grade designations including Nafion NR50, Aquivion PW79S, and Fumion F-950. Its primary function is proton conduction in hydrated or partially hydrated electrochemical environments. Ion exchange capacity is inversely proportional to equivalent weight; commercial grades commonly span 700–1500 g mol⁻¹ equivalent weight, corresponding to acid capacities from approximately 0.7 mmol g⁻¹ to 1.4 mmol g⁻¹ on a dry-resin basis. The material is differentiated from sulfonated aromatic hydrocarbon ionomers by its perfluorinated backbone, which imparts higher resistance to oxidative free-radical attack but increases equivalent weight requirements for comparable conductivity under low relative humidity.
Resin selection is governed by equivalent weight, ion exchange capacity, dissolution and dispersion behavior, acid-form thermal stability, and residual alkali-metal content. Equivalent weight determines the volumetric density of sulfonic acid sites and therefore the characteristic conductivity at a given hydration number. Ion exchange capacity is determined by titration of the sulfonic acid groups after equilibration in 1 M NaCl, and the value is expressed as millimoles per gram dry resin. Melt flow behavior, where relevant, is evaluated according to ISO 1133-1 under a specified load and temperature; because PFSA resins are thermally sensitive, the acid-form test temperature is commonly limited to 230 °C. Residual fluoride release during processing is monitored because thermal or hydrolytic decomposition generates hydrofluoric acid at temperatures above approximately 280 °C. Table 1 summarizes representative commercial grades and typical specification parameters drawn from manufacturer technical data sheets.
| Grade | Equivalent weight (g mol⁻¹) | Ion exchange capacity (mmol g⁻¹) | Supply form | Recommended acid-form processing limit (°C) |
|---|---|---|---|---|
| Aquivion PW79S | 790 | 1.26 | Powder / dispersion | 260 |
| Nafion NR50 | 800–1100 | 0.8–1.1 | Pellet / powder | 270 |
| Fumion F-950 | 950 | 1.05 | Powder | 250 |
Density of the acid-form resin typically falls between 1.9 g cm⁻³ and 2.1 g cm⁻³ when measured by ISO 1183-1, although the high fluorine content complicates conventional polymer density determination because air entrapment in powder beds lowers apparent density values. The glass transition region is broad and hydration-dependent; published data for this specific configuration is limited, but dynamic mechanical analysis scans from −50 °C to 150 °C show an alpha relaxation below 120 °C in the acid form.
Melt extrusion of PFSA acid-form resin requires corrosion-resistant contacting surfaces because trace hydrofluoric acid is released at elevated temperatures. In production, twin-screw extruders with 40:1 L/D ratio and all-316L stainless steel or Hastelloy C-276 barrels are used, with screw profiles configured for low-shear distributive mixing. Barrel temperatures are ramped from 180 °C at the feed throat to a maximum die temperature of 260 °C. Residence time above 250 °C is kept below 5 min to limit desulfonation and discoloration. Pre-drying is mandatory when the resin has been exposed to relative humidity above 60%; a vacuum dryer at 80 °C and 20 mbar for 4 h reduces moisture to below 0.05 mass% before extrusion. The use of amine-based stabilizers or lubricants is incompatible because the sulfonic acid group protonates the amine and forms an ionomeric salt that reduces melt flow and shifts equivalent weight. Dispersion casting is preferred over melt processing for membranes thinner than 50 μm because of gauge uniformity and avoidance of thermal history effects.
Solution-cast PFSA membranes are prepared from aqueous-alcoholic dispersions with solids content between 5 mass% and 25 mass%. Casting viscosity is controlled by the alcohol-to-water ratio and by the equivalent weight of the resin; higher equivalent weight grades require higher alcohol fractions to maintain a homogeneous dispersion. Slot-die coating on release liners is used for continuous membrane production, with drying zones operated from 60 °C to 150 °C under solvent recovery. Membrane thickness for automotive fuel cells is typically 10–25 μm, while chlor-alkali membranes are often reinforced with expanded polytetrafluoroethylene fabric and coated to 100–200 μm. Tensile properties of cast membranes are evaluated according to ASTM D638-14 or ISO 527-3, with typical reported tensile strength values of 20–40 MPa and elongation at break of 100–250% at 23 °C and 50% relative humidity. Proton conductivity is measured by four-electrode electrochemical impedance spectroscopy in the 0.1 Hz–1 MHz frequency range; fully hydrated membranes at 80 °C commonly show conductivity in the range of 0.05–0.15 S cm⁻¹ depending on equivalent weight and pre-treatment. The resin is also applied as a binder in catalyst layers, where the ionomer-to-carbon support ratio influences triple-phase boundary density and mass-transport overpotential.
Proton exchange membrane fuel cells and water electrolyzers represent the principal electrochemical applications of PFSA resin. In fuel cells, the membrane is assembled between gas diffusion electrodes at a hot-press temperature of 130–160 °C and pressure of 1–4 MPa for 3–5 min; the resin in the catalyst layer is activated by acid treatment in 1 M sulfuric acid at 80 °C followed by rinsing in deionized water. The low gas permeability of the hydrated film, measured in a permeation cell according to ASTM D1434, reduces crossover losses but does not eliminate them. In proton exchange membrane water electrolysis, PFSA membranes with equivalent weights below 1000 g mol⁻¹ are preferred because the higher acid density lowers ohmic drop at current densities above 1 A cm⁻². However, operation above 90 °C and at low anode water activity accelerates membrane thinning and fluoride release; published data for this specific configuration is limited to lifetime tests under controlled differential pressure.
When PFSA resin is compared with sulfonated polyetheretherketone, sulfonated polysulfone, or phosphoric-acid-doped polybenzimidazole, the differentiation points are proton conductivity at low relative humidity, oxidative stability, and processing economics. PFSA resins retain measurable conductivity at 30% relative humidity and 80 °C, whereas many hydrocarbon ionomers require ion exchange capacities above 2.0 mmol g⁻¹ to reach similar values, which increases water uptake and dimensional swelling. The perfluorinated backbone provides resistance to hydroxyl and peroxyl radicals generated during fuel cell operation; ex situ Fenton tests at 80 °C in 3% H₂O₂ with 2 ppm Fe²⁺ show lower mass loss for PFSA than sulfonated hydrocarbon membranes by roughly one order of magnitude. Conversely, PFSA resins have lower glass transition ranges in the acid form and require humidification to maintain conductivity above 100 °C, while phosphoric-acid-doped polybenzimidazole operates at 120–180 °C without external humidification but has lower voltage stability at low current density. Table 2 provides a comparative matrix of typical properties.
| Property | Test condition | PFSA resin | Sulfonated polyetheretherketone | Phosphoric-acid-doped polybenzimidazole |
|---|---|---|---|---|
| Proton conductivity (S cm⁻¹) | Fully hydrated, 80 °C | 0.05–0.15 | 0.01–0.10 | Not rated at 80 °C without humidification |
| Oxidative stability mass loss (%) | Fenton test, 3% H₂O₂, 2 ppm Fe²⁺, 80 °C, 24 h | <1 | 5–20 | <5 |
| Maximum continuous operating temperature (°C) | Humidified electrochemical cell | 80–120 | 80–120 | 120–180 |
| Dimensional swelling in water at 80 °C (%) | Gravimetric equilibrium uptake | 10–50 | 30–100 | <10 |
Beyond electrochemical energy conversion, PFSA resin is used as a solid acid catalyst or catalyst support in alkylation, esterification, and hydration reactions. The resin is typically activated by washing in 1 M mineral acid and drying at 110 °C under vacuum to remove adsorbed water from the sulfonic acid sites. Catalytic activity depends on acid site accessibility and solvent swelling; nonpolar solvents give lower apparent activity than water-alcohol mixtures because the resin remains in a collapsed state. In chlor-alkali electrolysis, PFSA membranes reinforced with polytetrafluoroethylene fabric are installed in zero-gap cells operating at 80–90 °C and 30–35 mass% NaOH catholyte; the membrane is oriented with the sulfonic-acid-rich layer facing the anode to reduce back-migration of hydroxide ions. Selection of equivalent weight below 1000 g mol⁻¹ reduces cell voltage at 6 kA m⁻² but increases swelling and may reduce mechanical durability under differential pressure.
Storage of PFSA resin in uncontrolled humidity leads to reversible moisture uptake of 5–15 mass% and, in the acid form, slow pickup of airborne ammonia or amine contaminants that neutralizes surface sulfonic acid groups. The resin should be stored sealed at ≤25 °C and ≤50% relative humidity. Before any thermal processing or conductivity measurement, the material is conditioned at 80 °C under vacuum until mass change is below 0.1 mass% over 24 h. Metallic contamination from stainless steel processing equipment can exchange with sulfonic acid protons; iron, chromium, and nickel contents above 20 ppm are associated with reduced proton conductivity and accelerated membrane degradation in oxidative environments. Use of brass, copper, or zinc-containing fittings is incompatible because multivalent cations form sulfonate salts that cannot be fully regenerated by standard acid washing. The material is also incompatible with strong reducing agents, alkali-metal hydroxides in the presence of organic solvents, and prolonged exposure to ionizing radiation above 50 kGy, which causes chain scission and loss of mechanical integrity. Final application suitability must be verified by testing the selected grade in the intended electrochemical or catalytic environment under relevant temperature, pressure, and humidity cycling.
