Bakelite is a phenol-formaldehyde plastic, the first fully synthetic one, patented in 1907, that cures under heat into a hard, rigid, dark material which insulates electricity, resists heat and chemicals, and cannot be remelted. It is the plastic to prioritise for electrical insulation, switch bodies and handles, though its feedstocks, phenol and formaldehyde, are toxic and need careful handling.
Part of Plastics and Polymers
Bakelite is the trade name of the first fully synthetic thermosetting plastic, a phenol-formaldehyde resin used as a molded electrical insulator.
The First Plastic Made Entirely From Chemicals
Casein and celluloid start from natural polymers. Bakelite is built from small molecules: phenol, a coal-tar product, and formaldehyde, made by oxidising methanol. Heating them together with a catalyst makes a resin, and heating the resin in a mold makes it set into a rigid network. The corpus’s carriers date it to 1907. The inventor was Leo Baekeland, which is recalled history and not corpus content.
Properties That Make It The Insulation Plastic
| Property | Value | Source |
|---|---|---|
| Volume resistivity | Above 10¹⁰ Ω·cm | Plastics from Scratch |
| Dielectric strength | 10-15 kV/mm | Plastics from Scratch |
| Heat resistance | About 300 °C | Plastics Manufacturing |
| Colour | Dark brown or black, can be dyed with pigment before curing | Plastics Manufacturing |
| Remeltable | No | Both |
Treat 300 °C as the temperature where it decomposes, not a service temperature. The dielectric strength is for a dry, flawless sample and real parts do worse: see Electrical Insulation.
It Is A Thermoset, And That Decides How You Use It
Once cured, Bakelite will not melt, so a cracked part cannot be remade and scrap is only filler. In exchange it holds its shape in heat. It is brittle when unfilled, so it is mixed with wood flour, cotton flock or fabric to take impact. See Phenolic Resins for the structure and Thermoplastic vs Thermoset for when to choose it.
The Route From Raw Material To Part
- Phenol: from coal tar or wood: Phenol Sources.
- Formaldehyde: from methanol: Formaldehyde Production.
- Resin and powder: Synthesis and Molding.
- Pressing: Compression Mold.
Salvage Comes Before Synthesis
Old dark switch plates, plug bodies, radio cabinets, telephone handsets, handles and knobs are often phenolic. Reuse them whole for insulating bases and handles. Grind unusable scrap for filler. Do not heat or burn old phenolic indoors, because it releases phenol and formaldehyde.
What You Need To Make It
- Phenol and formaldehyde of known strength
- A vessel that resists both and can be vented
- A heated steel mold and a press
- Wood flour or cotton flock filler
- Gloves, eye and face protection, and strong ventilation
Common Mistakes
- Treating it as a thermoplastic — it cannot be remelted or reworked.
- Skipping filler — unfilled parts crack.
- Heating phenol and formaldehyde in a sealed vessel.
- Burning scrap.
Phenol and formaldehyde
Phenol burns skin, can be painless at first, and is absorbed through the skin with systemic toxicity. Formaldehyde irritates the airway and is a carcinogen. The reaction releases heat and steam. Work outdoors or with strong ventilation, with eye and skin protection, and never in a closed vessel. See Phenol Sources.
What’s Next
- Learn next: Phenol Sources — the feedstock, and its hazard
- Combine with: Insulation and Tools — where Bakelite is used