SGL Sigracet 39BB is a carbon fiber paper used as a gas diffusion layer (GDL). The substrate is made water-repellent with 5% PTFE and carries a microporous layer (MPL) on one side. A GDL spreads gas to the catalyst layer, conducts electrons and helps remove water; the PTFE treatment reduces flooding of the pores. It is supplied as a 100 × 100 mm sheet.

39BB is thicker than 22BB (315 ± 20 µm) but has a low areal weight (about 95 g/m²) and high porosity. It is the most compressible SGL paper in this group (about 27% at 1 MPa). When a thick GDL is needed, it is a lighter and more compliant option than 38BC. Catalyst ink is normally coated on the MPL side; do not mix up the two faces.

Key Features

Water-repellent carbon fiber paper treated with 5% PTFE
Microporous layer (MPL) on one side
Thickness 315 ± 20 µm, areal weight 95 ± 15 g/m² (manufacturer data)
High porosity; compressibility about 27% (1 MPa)
Through-plane resistance < 13 mΩ·cm²; water contact angle above 130° on the MPL side
100 × 100 mm sheet
Cutting can release fine carbon fibers and dust; work in a well-ventilated area

Technical Specifications

Material	Non-woven carbon fiber paper (GDL)
Thickness	315 ± 20 µm
Areal weight	95 ± 15 g/m²
Porosity	High (maker's qualitative rating)
PTFE treatment	5% (substrate)
Microporous layer (MPL)	Yes, on one side
Through-plane resistance	< 13 mΩ·cm²
Gas permeability	1.5 Gurley s
Compressibility	About 27% (1 MPa)
Water contact angle (MPL)	> 130°
Size	100 × 100 mm