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PH-56; PD-56
Product Overview:
Polyester polyols are a crucial class of raw materials used in the formulation of C.A.S.E. (Coatings, Adhesives, Sealants, and Elastomers) products. They are polymers characterized by multiple hydroxyl (-OH) terminal groups and ester (-COO-) linkages in their backbone. Derived from the condensation reaction of polyacids (or anhydrides) and polyols, their chemical structure allows them to act as the "soft," flexible segment when reacted with isocyanates to form polyurethanes (PUs). The choice of polyester polyol directly dictates key end-product properties such as mechanical strength, hydrolytic stability, flexibility, chemical resistance, and adhesion.
Polyester polyols are synthesized via a polycondensation reaction between:
Polyacids (or Anhydrides):
Aromatic: Phthalic anhydride (PA), Isophthalic acid (IPA), Terephthalic acid (TPA). Impart rigidity, hardness, and better chemical/thermal resistance.
Aliphatic: Adipic acid (most common), Succinic acid, Glutaric acid. Impart flexibility and low-temperature performance.
Polyols (Glycols):
Short-chain/rigid: Ethylene Glycol (EG), Diethylene Glycol (DEG), 1,4-Butanediol (BDO). Contribute to hardness and high melting points.
Long-chain/flexible: Dipropylene Glycol (DPG), 1,6-Hexanediol (HDO), Neopentyl Glycol (NPG - imparts excellent hydrolytic stability).
The ratio of acid to glycol, the specific monomers chosen, and the manufacturing process (e.g., melt polycondensation) determine the final polyol's molecular weight, hydroxyl value (OH#), acid value, and functionality (typically 2 for linear, >2 for branched).
Polyester polyols are often compared to polyether polyols. Their advantages make them the preferred choice for many demanding applications:
Excellent Mechanical Properties: High tensile strength, tear resistance, and abrasion resistance. This is due to strong intermolecular forces (hydrogen bonding and dipole-dipole interactions between ester groups).
Superior Abrasion and Tear Resistance: Ideal for coatings and elastomers subject to wear and tear.
Good Solvent and Chemical Resistance: Resist a wider range of oils, fuels, and solvents than polyether-based PUs.
High Melting Points & Heat Resistance: Aromatic polyesters, in particular, offer good performance at elevated temperatures.
Strong Adhesion: The polar ester group promotes excellent adhesion to various substrates, especially metals and plastics.
Poor Hydrolytic Stability: This is their primary weakness. The ester bond is susceptible to cleavage in the presence of water (hydrolysis), especially under acidic or basic conditions and high heat. This can lead to polymer degradation and loss of properties over time.
Higher Viscosity: Generally more viscous than polyether polyols of equivalent molecular weight, which can complicate processing and handling.
Cost: Often more expensive than polyether polyols due to raw material and manufacturing costs.
Mitigation Strategy for Hydrolysis: Use hydrolytically stable monomers like Isophthalic Acid (IPA) and Neopentyl Glycol (NPG). NPG is especially effective as it lacks hydrogens beta to the ester group, preventing a common degradation pathway.
The properties of polyester polyols make them indispensable in specific high-performance segments:
| C.A.S.E. Segment | Application Examples | Why Polyester Polyol is Used |
|---|---|---|
| Coatings | Automotive OEM & Refinish Clearcoats, industrial maintenance coatings, plastic coatings, coil coatings. | Excellent hardness, mar resistance, UV durability (with aliphatic isocyanates), and chemical resistance against fuels and solvents. |
| Adhesives | Laminating adhesives (food packaging), shoe sole bonding, automotive structural adhesives. | Strong adhesion to diverse substrates, high strength, and heat resistance for flexible packaging laminates. |
| Sealants | High-performance construction sealants, industrial sealants. | Good mechanical properties and balance of flexibility/strength. |
| Elastomers | Cast elastomers (industrial wheels, rolls, gaskets), thermoplastic polyurethane (TPU) for films and cables. | Superior abrasion resistance, load-bearing capacity, tear strength, and cut resistance. |
| Property | Polyester Polyols | Polyether Polyols |
|---|---|---|
| Hydrolytic Stability | Poor | Excellent |
| Microbial Resistance | Poor | Excellent |
| Mechanical Strength | Excellent (Tensile, Tear) | Good |
| Abrasion Resistance | Excellent | Good |
| Low-Temp Flexibility | Good (depends on type) | Excellent |
| Chemical Resistance | Excellent (oils, solvents) | Fair to Good |
| Viscosity | High | Low |
| Cost | Higher | Lower |
6. Parameters:
| Product Model | Hydroxyl value (mgKOH/g) | Acid Value (mgKOH/g) | Moisture (%) | Viscosity (CPS 25℃) |
| PH-56 | 56±3 | ≤1.0 | ≤0.05 | 1800 100℃ |
| PD-56 | 56±3 | ≤2.0 | ≤0.05 | 1200-1300 100℃ |
Product Overview:
Polyester polyols are a crucial class of raw materials used in the formulation of C.A.S.E. (Coatings, Adhesives, Sealants, and Elastomers) products. They are polymers characterized by multiple hydroxyl (-OH) terminal groups and ester (-COO-) linkages in their backbone. Derived from the condensation reaction of polyacids (or anhydrides) and polyols, their chemical structure allows them to act as the "soft," flexible segment when reacted with isocyanates to form polyurethanes (PUs). The choice of polyester polyol directly dictates key end-product properties such as mechanical strength, hydrolytic stability, flexibility, chemical resistance, and adhesion.
Polyester polyols are synthesized via a polycondensation reaction between:
Polyacids (or Anhydrides):
Aromatic: Phthalic anhydride (PA), Isophthalic acid (IPA), Terephthalic acid (TPA). Impart rigidity, hardness, and better chemical/thermal resistance.
Aliphatic: Adipic acid (most common), Succinic acid, Glutaric acid. Impart flexibility and low-temperature performance.
Polyols (Glycols):
Short-chain/rigid: Ethylene Glycol (EG), Diethylene Glycol (DEG), 1,4-Butanediol (BDO). Contribute to hardness and high melting points.
Long-chain/flexible: Dipropylene Glycol (DPG), 1,6-Hexanediol (HDO), Neopentyl Glycol (NPG - imparts excellent hydrolytic stability).
The ratio of acid to glycol, the specific monomers chosen, and the manufacturing process (e.g., melt polycondensation) determine the final polyol's molecular weight, hydroxyl value (OH#), acid value, and functionality (typically 2 for linear, >2 for branched).
Polyester polyols are often compared to polyether polyols. Their advantages make them the preferred choice for many demanding applications:
Excellent Mechanical Properties: High tensile strength, tear resistance, and abrasion resistance. This is due to strong intermolecular forces (hydrogen bonding and dipole-dipole interactions between ester groups).
Superior Abrasion and Tear Resistance: Ideal for coatings and elastomers subject to wear and tear.
Good Solvent and Chemical Resistance: Resist a wider range of oils, fuels, and solvents than polyether-based PUs.
High Melting Points & Heat Resistance: Aromatic polyesters, in particular, offer good performance at elevated temperatures.
Strong Adhesion: The polar ester group promotes excellent adhesion to various substrates, especially metals and plastics.
Poor Hydrolytic Stability: This is their primary weakness. The ester bond is susceptible to cleavage in the presence of water (hydrolysis), especially under acidic or basic conditions and high heat. This can lead to polymer degradation and loss of properties over time.
Higher Viscosity: Generally more viscous than polyether polyols of equivalent molecular weight, which can complicate processing and handling.
Cost: Often more expensive than polyether polyols due to raw material and manufacturing costs.
Mitigation Strategy for Hydrolysis: Use hydrolytically stable monomers like Isophthalic Acid (IPA) and Neopentyl Glycol (NPG). NPG is especially effective as it lacks hydrogens beta to the ester group, preventing a common degradation pathway.
The properties of polyester polyols make them indispensable in specific high-performance segments:
| C.A.S.E. Segment | Application Examples | Why Polyester Polyol is Used |
|---|---|---|
| Coatings | Automotive OEM & Refinish Clearcoats, industrial maintenance coatings, plastic coatings, coil coatings. | Excellent hardness, mar resistance, UV durability (with aliphatic isocyanates), and chemical resistance against fuels and solvents. |
| Adhesives | Laminating adhesives (food packaging), shoe sole bonding, automotive structural adhesives. | Strong adhesion to diverse substrates, high strength, and heat resistance for flexible packaging laminates. |
| Sealants | High-performance construction sealants, industrial sealants. | Good mechanical properties and balance of flexibility/strength. |
| Elastomers | Cast elastomers (industrial wheels, rolls, gaskets), thermoplastic polyurethane (TPU) for films and cables. | Superior abrasion resistance, load-bearing capacity, tear strength, and cut resistance. |
| Property | Polyester Polyols | Polyether Polyols |
|---|---|---|
| Hydrolytic Stability | Poor | Excellent |
| Microbial Resistance | Poor | Excellent |
| Mechanical Strength | Excellent (Tensile, Tear) | Good |
| Abrasion Resistance | Excellent | Good |
| Low-Temp Flexibility | Good (depends on type) | Excellent |
| Chemical Resistance | Excellent (oils, solvents) | Fair to Good |
| Viscosity | High | Low |
| Cost | Higher | Lower |
6. Parameters:
| Product Model | Hydroxyl value (mgKOH/g) | Acid Value (mgKOH/g) | Moisture (%) | Viscosity (CPS 25℃) |
| PH-56 | 56±3 | ≤1.0 | ≤0.05 | 1800 100℃ |
| PD-56 | 56±3 | ≤2.0 | ≤0.05 | 1200-1300 100℃ |
