Laminated Phenolic Paper Sheet: Bakelite-Coated Kraft Paper Hot-Pressed and Baked (O'Conor, Westinghouse 1918)

Paper coated with liquid bakelite, stacked and hot-pressed becomes a hard insulating board. This is Westinghouse's process (O'Conor, US 1,284,432, 1918): kraft paper coated on one side, dried, stacked, pressed hot up to 800 psi, cooled under pressure, then baked clamped at 100–140 °C for about eight hours. The plate is hard, barely takes up water, can be turned and bored like wood, and stands 150 °C continuously. Uncured bakelite gives off phenol and formaldehyde: ventilate. The picture: our diagram.