Nafion 115 is a perfluorosulfonic acid (PFSA) proton exchange membrane that conducts protons (H⁺) and other cations while separating the anode and cathode. It is extrusion-cast, nominally 127 µm (5 mil) thick, and supplied as a 100 × 100 mm sheet.

Thickness is a trade-off in the Nafion family: thin grades (212: 50.8 µm, 211: 25.4 µm) have lower resistance but are more delicate and allow more gas/fuel crossover; thick grades (115: 127 µm, 117: 183 µm) are more robust and limit crossover better, at higher ionic resistance. Nafion 115 is the medium-thick option among these four membranes: lower resistance than 117, more robust and less permeable than 212 and 211. It is a balanced choice for electrolysis and cell experiments that need a durable membrane that is easy to handle and cut.

Key Features

Nominal thickness 127 µm (5 mil), basis weight 250 g/m² (manufacturer data)
Extrusion-cast PFSA membrane in the acid (H⁺) form
Conductivity at least 0.10 S/cm; available acid capacity at least 0.90 meq/g (manufacturer data)
Thinner than Nafion 117 (lower resistance), thicker than Nafion 212/211 (more robust, less crossover)
Swells about 10% (23 °C) to 15% (100 °C) when wet; allow for this in gaskets and cutting size
Common pretreatment: boiling in 3% H₂O₂ and in 0.5 M H₂SO₄, rinsing with pure water after each step (protocols vary by application)
100 × 100 mm sheet; can be cut to size

Technical Specifications

Membrane type	Proton (cation) exchange membrane, PFSA
Production method	Extrusion-cast
Nominal thickness	127 µm (5 mil)
Basis weight	250 g/m² (manufacturer data)
Conductivity	At least 0.10 S/cm (manufacturer data)
Acid capacity	Available at least 0.90 meq/g; total 0.95–1.01 meq/g
Water uptake	38% (dry to water at 100 °C, 1 h; manufacturer data)
Wet expansion	Linear, about 10% (23 °C) – 15% (100 °C)
Tensile strength	43 / 32 MPa (MD / TD, 50% RH, 23 °C)
Operating temperature	Conductivity falls if it dries out above about 80 °C
Form	Acid (H⁺) form (manufacturer data)
Size	100 × 100 mm