Plastics from Scratch

7 min read

Plastics from Scratch

Phase 5 — Rebuilding Technology

Producing basic polymers from available materials. Plastics are the essential insulating, forming, and coating material for electrical work, and replace scarce materials (ivory, tortoiseshell, horn) for countless small parts. Three plastics are producible from scratch: casein, celluloid, and Bakelite.

Why This Matters

The single most important application of early plastics is electrical insulation. Without insulating material, you can’t make:

  • Insulated wire (the basis of all electrical equipment)
  • Switch bodies and terminal blocks
  • Capacitor dielectrics
  • Transformer bobbins

Beyond electrical work, plastics replace materials that are scarce, expensive, or difficult to work: buttons, combs, handles, knobs, gears, bearings, and containers.

Polymer Basics

Thermoplastics (celluloid): Soften when heated, harden when cooled. Can be reshaped repeatedly. Useful for molding and forming.

Thermosets (Bakelite, hardened casein): Set permanently when cured. Cannot be reshaped. Harder, more heat-resistant, better for electrical and structural applications.

Casein Plastic (Galalith)

The simplest plastic to produce. Made from milk protein.

Casein Extraction

  1. Heat skim milk to 40°C
  2. Add acid (vinegar, 10% by volume, or dilute hydrochloric acid)
  3. Casein precipitates as white curds
  4. Filter through cloth and press out whey
  5. Wash curds 2–3 times with clean water
  6. Press into a dense mass — this is raw casein

Yield: ~30 grams of casein per liter of skim milk.

Formaldehyde Hardening

  1. Mold the wet casein into the desired shape (press into molds or roll into sheets)
  2. Immerse in a 5–10% formaldehyde solution
  3. Soak for days to weeks, depending on thickness:
    • 1 mm sheet: 2–3 days
    • 5 mm block: 2–3 weeks
    • 10 mm block: 4–6 weeks
  4. The formaldehyde crosslinks the protein chains, hardening the plastic
  5. Dry slowly at room temperature (rapid drying causes warping and cracking)

Formaldehyde is toxic

Formaldehyde vapor irritates eyes, throat, and lungs, and is a carcinogen with chronic exposure. Work in well-ventilated areas. Wear eye protection. Keep solutions covered when not in use.

Properties and Uses

Casein plastic can:

  • Be polished to a high gloss
  • Be dyed any color
  • Be machined (drilled, turned, cut)
  • Replace horn, bone, and ivory for buttons, beads, and decorative items

Casein plastic cannot:

  • Withstand water immersion (softens and warps)
  • Handle temperatures above 80°C
  • Serve as structural material (too brittle)
  • Provide electrical insulation (absorbs moisture)

Best uses: Buttons, knitting needles, beads, small decorative items, pen bodies.

Celluloid (Cellulose Nitrate)

The first true thermoplastic. Invented 1856. Moldable, transparent (when thin), and strong.

Cellulose Nitration

Materials:

  • Cotton linters or pure wood-pulp cellulose
  • Concentrated nitric acid (>65%)
  • Concentrated sulfuric acid (>90%)

Extreme chemical hazard

Concentrated nitric and sulfuric acids cause severe burns on contact. The nitration reaction can run away explosively if temperature exceeds 40°C. This process requires careful temperature control, proper PPE (acid-resistant gloves, goggles, face shield, apron), and immediate access to large quantities of water for emergency washing.

Process:

  1. Mix nitric and sulfuric acids in a 1:2 ratio by volume at <20°C (ice bath)
  2. Add dry cellulose slowly while stirring
  3. Keep temperature below 30°C throughout (exothermic reaction — will run away if too hot)
  4. Soak for 15–30 minutes
  5. Remove cellulose, wash in running water for 24+ hours (remove ALL acid — residual acid causes spontaneous decomposition)
  6. Result: cellulose nitrate (gun cotton / pyroxylin)

Camphor Plasticizer

Cellulose nitrate alone is too hard and brittle. Camphor makes it plastic:

  1. Camphor source: Distill from camphor tree wood, or synthesize from turpentine (pinene → camphene → isoborneol → camphor)
  2. Mix cellulose nitrate with 25–30% camphor by weight
  3. Add a small amount of solvent (ethanol or ethyl acetate)
  4. Knead thoroughly on warm rollers (60–70°C) — the mixture becomes a smooth, plastic mass
  5. Roll into sheets or press into molds at 80–100°C
  6. Cool to harden

Safety

Celluloid burns violently

Cellulose nitrate is essentially smokeless gunpowder with a plasticizer. It ignites easily, burns fiercely, and cannot be extinguished with water. Never machine celluloid near sparks or flame. Store away from heat. This material is unsuitable for any application near heat or electrical arcing.

Applications: Transparent sheets (windows for instruments), combs, handles, photographic film base, lacquer (dissolved in solvent). Do NOT use for electrical insulation — the flammability is disqualifying.

Bakelite (Phenol-Formaldehyde)

The most useful of the three plastics for a rebuilding community. Heat-resistant, electrically insulating, chemically inert, and mechanically strong.

Phenol Sources

From coal tar: Destructive distillation of coal produces tar. Distill the tar; the fraction boiling at 180–185°C is crude phenol. Purify by crystallization (phenol melts at 41°C — cool slowly, collect crystals).

From wood: Destructive distillation of hardwood produces pyroligneous acid containing small amounts of phenol and cresols. Lower yield but universally available.

Formaldehyde Production

Oxidize methanol over a catalyst:

  1. Methanol source: Destructive distillation of wood produces “wood alcohol” (methanol) in the first distillate fraction
  2. Pass methanol vapor mixed with air over a heated copper or silver gauze (500–600°C)
  3. CH₃OH + ½O₂ → HCHO + H₂O
  4. Collect the formaldehyde as a ~37% solution in water (formalin)

Bakelite Synthesis

Stage A (Novolac — soluble, fusible):

  1. Mix phenol and formaldehyde in a 1:0.8 molar ratio (roughly equal weights)
  2. Add 1–2% acid catalyst (hydrochloric or oxalic acid)
  3. Heat to 100°C with stirring for 2–4 hours
  4. The mixture thickens to a viscous resin
  5. Pour into trays, cool, and grind into powder

Stage B (with filler — moldable):

  1. Mix novolac powder with 8–10% hexamethylenetetramine (“hexa” — the additional crosslinker)
  2. Add filler: wood flour (50–60% by weight), cotton flock, or asbestos fiber
  3. Wood flour filler produces a machinable, impact-resistant material
  4. Mix thoroughly in a ball mill or by kneading

Stage C (Molding — final cure):

  1. Load powder into a preheated steel mold (160–180°C)
  2. Apply pressure (10–30 MPa) in a hydraulic press
  3. Hold for 1–5 minutes per mm of thickness
  4. The resin crosslinks permanently — the part cannot be reshaped
  5. Open mold, extract part, trim flash

Molding Techniques

Compression Molding

The standard method for Bakelite and casein:

  1. Steel mold (two-part) machined to final part shape
  2. Calculate charge weight: part volume × material density × 1.05 (overfill slightly)
  3. Pre-heat mold in oven
  4. Load charge, close mold in press
  5. Apply heat and pressure per material requirements
  6. After cure time, open and extract

Casting

For phenol-formaldehyde or casein:

  1. Mix liquid resin (Stage A novolac with alkaline catalyst for casting grade)
  2. Pour into a mold at room temperature
  3. Cure slowly: 60°C for 24 hours, then ramp to 80°C for another 24 hours
  4. Slow curing prevents bubbles and cracking
  5. Result: clear amber (Bakelite) or translucent white (casein)

Machining

All three plastics machine well:

  • Use sharp HSS tools
  • Low cutting speed (half what you’d use for brass)
  • No coolant for celluloid (water causes swelling)
  • Bakelite produces abrasive dust — wear a mask

Practical Applications

Electrical Insulation (Priority #1)

Bakelite is the material of choice:

  • Switch and outlet bodies
  • Terminal strips and junction blocks
  • Transformer and coil bobbins
  • Capacitor dielectrics
  • Wire insulation (Bakelite lacquer)

Insulation properties: Volume resistivity >10¹⁰ Ω·cm, dielectric strength 10–15 kV/mm. Adequate for all power and signal applications up to several kilovolts.

Lacquers and Coatings

Dissolve celluloid in acetone or amyl acetate for a fast-drying, waterproof lacquer. Brush or spray onto:

  • Metal surfaces (corrosion protection)
  • Fabric (waterproofing)
  • Wood (moisture barrier)
  • Wire (thin insulating coating — dip and dry repeatedly)

What’s Next

With plastics production capability:

  • Insulate all electrical wiring and equipment
  • Mold switch bodies, connectors, and terminal blocks
  • Produce waterproof coatings and lacquers
  • Replace scarce natural materials with molded plastic
  • Build toward more advanced polymers as chemistry capability grows