Dupont's Nafion® N438 is a new product in the 400 series family. This membrane represents the state-of-the art in fabric reinforced cation exchange membranes. It has a new PTFE monofilament reinforcement with high strength but flatter profile than Nafion N424. Nafion N438's edge leakage is reduced and expansion characteristics are more uniform than N424.
Nafion N-424 is shipped in the "DRY" H+ form. "DRY" H+ membranes require simple pre-treatment in alkaline water. Refer to Nafion Technical Bulletin No. 93-01 for "DRY" H+ membrane pretreatment.
Please note: The side marked CATH must be installed facing the cathode, otherwise, the membranes will be irreversibly damaged in use. If your membrane is not marked simply feel both sides of the membrane, the rougher side will be the cathode side while the smoother side is the anode side.