bakelite material as per IEEE

Bakelite is the original, but now just one of the tradenames for reinforced phenolics. It's a thermoset made from a reaction of phenol and formaldehyde. Other tradenames include Durez and Plenco. Various fillers are used to obtain specific electrical and mechanical properties. Typical fillers are wood flour, cotton, canvas, glass fiber, nylon, etc., resulting in the various grades which are covered by ASTM D709 and NEMA (National Electrical Manufacturers Association) LI1 in the U.S.

Google Bakelite for additional information.