Phenolic Resole Resin (Liquid, pH 7-8)
Key Features
- Highest FST performance in thermoset category (LOI >65%)
- Meets FAR 25.853 (aircraft), EN 45545-2 (railway), IMO FTP (marine)
- Self-curing on heating (>120°C) — no separate hardener required
- Excellent thermal stability (char retention up to 600°C+)
- Compatibility with glass, carbon, and natural fibers
Phenolic Resole Resin (liquid grade) is a thermosetting phenol-formaldehyde resin produced under alkaline conditions (base-catalyzed condensation) with excess formaldehyde relative to phenol (F/P molar ratio 1.2-2.0). The resole structure contains methylol groups (-CH2OH) that enable self-condensation cure without external hardener upon heating above 120-150°C or with acid catalyst at lower temperatures. Free phenol content is <3% and free formaldehyde <1% in standard industrial grades.
Liquid resole resins at 50-75% solids in water or alcohol are the primary matrix resin for phenolic composite laminates with the best fire-smoke-toxicity (FST) performance available in thermoset matrices. Cured phenolic laminates meet the most stringent fire requirements: UL94 V-0, FAR 25.853 (aircraft interior), EN 45545-2 (railway), IMO FTP Code (marine), and BS 6853 (UK rail). The limiting oxygen index (LOI) of cured phenolic resin is >65%, versus 25-30% for polyester and 22-28% for epoxy.
Key industrial applications include fire-resistant composite panels for aircraft interior, train interior, and marine vessel structures; glass/phenolic laminates (GPO-3, G-7, G-9 grades) for electrical insulation boards; friction materials (brake pads, clutch linings); abrasive wheels and coated abrasives; foundry sand binder; and wood composite board (plywood, particle board) binder.
Specifications
| Parameter | Value |
|---|---|
| pH | 7-8 |
| Appearance | Amber to dark brown liquid |
| Free Phenol | <3% |
| Solids Content | 50-75 wt% |
| Free Formaldehyde | <1% |
| Viscosity (25°C) | 100-2,000 mPa·s (grade dependent) |
| Limiting Oxygen Index (cured) | >65% |
Applications
FAQ
Phenolic resole laminates require elevated temperature and pressure cure due to the condensation cure mechanism (releasing water vapor) and the need to suppress void formation from steam. Standard autoclave cure: (1) prepreg lay-up on matched die or over mandrel; (2) vacuum bag, apply 5-7 bar press pressure or autoclave pressure; (3) heat to 150°C at 2-3°C/min; (4) hold 150°C/1h; (5) ramp to 180°C/1h for full cure; (6) cool under pressure to 60°C before release. Press cure uses matched metallic molds at 5-15 MPa pressure. The high pressure is essential — without it, steam voids form and create >5% void content, severely impairing mechanical properties. Phenolic laminates cannot be vacuum-bag-only cured without significant void content due to the condensation byproduct.
Direct Contact
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