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Views: 0 Author: Site Editor Publish Time: 2025-06-11 Origin: Site
Polyester polyols are key components in the formulation of spray rigid polyurethane foams (PUR/PIR), contributing to properties such as rigidity, thermal stability, and adhesion. Here’s an overview of their role and characteristics in spray foam applications:
Rigidity & Strength: Polyester polyols enhance mechanical strength and dimensional stability.
Thermal Resistance: They improve high-temperature performance, making them suitable for insulation.
Adhesion: Excellent bonding to substrates (metal, wood, concrete).
Flame Retardancy: Often used with additives to meet fire safety standards (e.g., ASTM E84, UL 94).
Low Viscosity: Ensures easy processing in spray equipment.
Hydroxyl Value (OHV): Typically 150–400 mg KOH/g, affecting crosslinking density and foam hardness.
Acid Value: Low (<5 mg KOH/g) to avoid reaction interference.
Compatibility: Blends well with isocyanates (e.g., PMDI) and additives (surfactants, catalysts, flame retardants).
Aromatic Polyesters: Derived from phthalic anhydride/terephthalic acid (high rigidity, good fire resistance).
Aliphatic Polyesters: From adipic acid (more flexible, but less common in rigid foams).
Bio-based Polyesters: Sustainable options from renewable resources (e.g., soybean oil derivatives).
| Component | Function | Typical Content |
|---|---|---|
| Polyester Polyol | Base resin (OH provider) | 40–60% |
| PMDI (Isocyanate) | Reactant (NCO provider) | 40–60% |
| Blowing Agent | Foam expansion (e.g., HFC-245fa, water) | 5–15% |
| Catalyst | Reaction control (amine/metals) | 0.5–2% |
| Surfactant | Cell stabilization (e.g., silicone) | 1–3% |
| Flame Retardant | Fire resistance (e.g., TCPP) | 10–20% |
| Property | Polyester Polyol | Polyether Polyol |
|---|---|---|
| Mechanical Strength | Higher | Lower |
| Thermal Stability | Better | Moderate |
| Hydrolytic Stability | Lower (sensitive to moisture) | Higher |
| Cost | Often higher | Lower |
Building Insulation (walls, roofs, cold storage).
Industrial Tanks & Pipelines (cryogenic insulation).
Transportation (refrigerated trucks, marine insulation).
Moisture Sensitivity: Store in dry conditions; use sealed containers.
Viscosity: Pre-heating may be needed for spray processing.
Compatibility: Optimize with catalysts (e.g., amine-based for faster cure).
Polyester polyols are ideal for high-performance rigid spray foams requiring strength, thermal resistance, and adhesion. Proper formulation balancing OHV, viscosity, and additives is critical for sprayability and end-use performance.
