Polymers are materials made of very long chains of repeating units, and they matter to a rebuilding settlement because they can be molded, they insulate electricity, and they replace scarce materials such as ivory, horn and tortoiseshell for small parts. Three plastics can be made from scratch: casein from milk, celluloid from cellulose, and Bakelite from phenol and formaldehyde, with insulation the first job to give them.
Part of Plastics and Polymers
Polymers are large molecules built from repeating units; plastics are the polymers that can be shaped, and the early ones were made from milk, plant fibre and coal tar.
Insulation Is The Reason To Start
The most important application of early plastics is electrical insulation. Without an insulating material there is no insulated wire, switch body, terminal block, capacitor dielectric or transformer bobbin. Plastics from Scratch puts this first, ahead of the second job of replacing materials that are scarce, expensive or hard to work: buttons, combs, handles, knobs, gears, bearings and containers.
A Polymer Is A Chain; The Chain Sets The Behaviour
A polymer is a chain of linked units. Some chains are tied to each other and some are not, and that difference sorts every plastic into one of two families:
- Thermoplastics (celluloid) soften when heated and harden when cooled. They can be reshaped repeatedly, which suits molding and forming.
- Thermosets (Bakelite, hardened casein) set permanently when cured. They cannot be reshaped, and they are harder, more heat-resistant and better for electrical and structural use.
The full comparison is in Thermoplastic vs Thermoset, and the chain structure behind it in Chain Structure.
The Three Plastics A Settlement Can Make
| Plastic | Source | Best at | Not for |
|---|---|---|---|
| Casein (Galalith) | Milk protein | Buttons, beads, pen bodies | Water, heat, insulation |
| Celluloid | Cotton or wood-pulp cellulose | Sheets, combs, lacquer | Anything near heat or electrical arcing |
| Bakelite | Phenol and formaldehyde | Electrical insulation, handles | Anything needing re-shaping |
The plastics-from-scratch carrier calls Bakelite the most useful of the three for a rebuilding community: it is heat-resistant, electrically insulating, chemically inert and mechanically strong.
What You Need To Begin
- A heat source you can control, because every plastic here is shaped with heat.
- Molds that suit the process: Molding Techniques.
- Feedstock safety knowledge: acids, phenol, formaldehyde and solvents are all hazardous.
- A way to test the result, at least for insulation: Electrical Insulation.
Common Mistakes
- Making celluloid first because it sounds simple — it is the most hazardous of the three.
- Treating casein as waterproof — it softens and warps in water.
- Expecting to rework Bakelite — it will not remelt.
Every route involves a hazard
Celluloid needs strong acids and its product burns violently. Bakelite needs phenol, which burns skin and is absorbed through it, and formaldehyde, which is a respiratory irritant and carcinogen. Casein hardening uses formaldehyde solution. Work outdoors or with strong ventilation, with eye and skin protection.
What’s Next
- Learn next: Chain Structure — why chains behave differently
- Combine with: Bakelite — the first plastic to make for insulation