Terminology

• Novolac: formaldehyde:phenol ratio below 1; needs a curing agent
• Resole: ratio above 1, about 1.5; cures without a crosslinker
• Hexamethylenetetramine: hardener for novolac above 90°C
• Bakelite: early phenolic plastic

History and demand

Sourcing

• 2022 production: China 1.3 million tons, the United States 853,000 tons, and India 527,000 tons (IndexBox)

Composition and production

Raw materials

• Phenol and formaldehyde; base-catalyzed reaction rate peaks at about pH 10

Manufacturing process

• Resole first stage at about 70°C (158°F); cross-links on heating to about 120°C (248°F), releasing water
• Novolac bridges form with hexamethylenetetramine above 90°C (194°F)

Grades and types

• Novolac: molecular weight in the low thousands, about 10 to 20 phenol units
• Resole: one-step resin

Properties

Fire behavior

• No melting point; decomposes at 220°C (428°F) and above, the basis for weather- and boil-proof plywood
• Pyrolyzes and absorbs heat in ablative heat shields at 1,000 to 2,000°C

Uses in buildings

Building elements

• Resoles bond exterior plywood, oriented strand board, and engineered high-pressure laminate

Pros and cons

Pros

• Does not melt; boil- and weather-proof bonds
• One-step resole cures without a crosslinker

Sustainability

Recycled content and end of life

• White rot fungus and Rhodococcus phenolicus can biodegrade phenolic resin

Manufacturing and cost

Main manufacturers and suppliers

• Hexion

Sources

• Wikipedia: Phenol formaldehyde resin, https://en.wikipedia.org/wiki/Phenol_formaldehyde_resin
• Wikimedia Commons: Phenolic resin.jpg, photo by Acheolg (CC BY-SA 4.0), https://commons.wikimedia.org/wiki/File:Phenolic_resin.jpg
• IndexBox: phenolic resins in primary forms, market analysis, https://indexbox.co.uk/search/phenolic-resins-market/