Making Bakelite

Materials: ★★★ Requires materials not commonly found in school laboratories
Difficulty: ★★★ Requires a more experienced teacher
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff

Categories: Materials, Polymers

Alternative titles: Phenol-Formaldehyde Condensation Polymer

Summary

Phenol and formaldehyde are mixed with a small amount of catalyst and heated to drive a condensation reaction that first forms a syrupy resol and then cures to a hard, crosslinked thermoset known as bakelite. If placed in a warm mold, the resin sets into a rigid, heat-resistant plastic part.

Procedure

See links below for full method.

Links

Making Bakelite - Periodic Table of Videos - Periodic Videos:

Making World's First Plastic - Prussian Blue:

Variations

None

Safety Precautions

Work in a fume hood; formaldehyde is toxic and a probable carcinogen, and phenol is highly corrosive and readily absorbed through skin.
Wear splash goggles, face shield for pouring, lab coat, and chemical-resistant gloves rated for phenol and formaldehyde; change gloves immediately if contaminated.
Control heating; the reaction can exotherm and foam. Use small batches, a thermometer, and a heat shield.
Keep ignition sources away from flammable solvents or vapors that may be present.
Hot molds and resin can cause burns; handle with heat-resistant gloves and allow full cooling before opening.
Avoid creating dust when cutting or sanding cured parts; use local exhaust and a particulate mask if machining.
Collect phenol and formaldehyde containing wastes in labeled hazardous waste containers for proper disposal.

Questions to Consider

What type of polymerization forms bakelite? (Condensation polymerization producing water as a by-product during crosslinking)
Why does the resin turn from clear to opaque during curing? (Growing molecular weight and crosslink density cause phase changes and light scattering)
How does a thermoset differ from a thermoplastic upon reheating? (Thermosets do not melt; their covalent crosslinks prevent flow, while thermoplastics soften and can be remolded)
What is the role of the catalyst in this synthesis? (It accelerates formation of methylene and ether bridges between phenol rings, controlling resin type and cure rate)
Why are fillers often added to phenolic resins? (They improve toughness, dimensional stability, machinability, and reduce shrinkage and cost)