Overview

In the past, bipolar plates made of graphite were commonly used in fuel cells. They suffered from poor mechanical properties and the need for expensive machining to form the bolt holes, gas channels, the manifolds, and the small openings to connect the two. Entegris is now offering bipolar plates based on moldable, conductive polymer composition. Similar plates had been introduced earlier by DuPont. Entegris is willing to custom mold gas flow fields, etc. into these plates. Inexpensive, mass-produced bipolar plates now appear to the possible. The properties of these plates are described below (from an Entegris brochure).

The values given below for electrical and thermal conductivities are material values (like the density), independent of the dimensions of the object. The z-plane refers to values measured perpendicular to the sheet. To convert these material values to values of a given object, the value of 0.02 ohm*cm for resistivity for instance is multiplied with the thickness of 0.25 cm to result in a through plane (or area) resistance of 0.005 ohm*cm ². This again multiplied with a current density of 0.6 A/cm ² would give a voltage drop of 3 mV through the sheet.

• Flexure modulus at 90 C 8 GPa 1.18 10 ⁶ psi ASTM D-790

• Impact strength, notched.0.16 N m/cm 0.30 ft lb/in. ASTM D-256

• Compressive strength 95 MPa 14 10 ³ psi

• Compressive creep 0.035% at 200 hours, 200 psi, 90 C

• Electrical properties

• Electrical conductivity/resistivity ( z-plane)

• 50 10 S/cm...