How phenolic resin is made
This was the first commercial synthetic resin. Its biggest job today is gluing plywood together.
- stations
- 5
- things upstream
- 13
- raw sources
- 5
- steps from the ground
- 6
The short version
Phenol and formaldehyde, heated together with a catalyst, build a soft prepolymer. Excess phenol with an acid gives a solid novolac, and excess formaldehyde with a base gives a liquid resole. Heat and pressure then cross-link either one into a hard, heat-resistant solid that will never melt again, found in plywood, billiard balls and brake linings.
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Charge the reactor
Phenol and formaldehyde go into a vessel with a catalyst. The ratio decides the product. Excess phenol with an acid heads for novolac, and excess formaldehyde with a base in water heads for resole.
Goes in -
Cook the prepolymer
Heating attaches formaldehyde to the phenol rings, then links the rings into short chains of about 10 to 20 units. The reaction stops well before the batch sets solid.
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Grind the solid grade
Cooled novolac is a solid that can still soften with heat. It is ground to powder. Resole usually stays liquid or in solution, ready to spread between wood veneers.
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Add filler and hardener
Molding powders get fillers such as wood flour, minerals or glass fibers, plus a hardener such as hexamethylenetetramine, which supplies formaldehyde when hot. The filler adds strength to a resin that would otherwise be brittle.
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Cure under heat and pressure
A pressurized hot mold or a veneer press finishes the job. Cross-links form throughout, creating a network that cannot melt or dissolve. Baekeland's insight was that pressure stops the batch foaming into a brittle mess.
Worth repeating
- Leo Baekeland began this research after selling the rights to his Velox photographic paper to Eastman Kodak for $750,000.
- Baekeland's first goal was a replacement for shellac, a material made from the secretion of lac insects.
- Baekeland filed for his Bakelite process in 1907, and it was the first synthetic thermosetting plastic.
Back to the ground
Follow every input upstream and phenolic resin starts as these 5 raw sources.
Where it goes next
Phenolic resin feeds 3 lines directly and reaches 171 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How phenolic resin is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/phenolic-resin