Polyester polyols

Chemical structure

The structure of polyester polyols is characterised by the presence of numerous ester bonds (–COO–) and active hydroxyl groups, which react with isocyanates to form urethane bonds (–NH–CO–O–), which form the basis of the polyurethane structure.

Aliphatic polyester polyols

They are obtained from aliphatic dicarboxylic acids and glycols and are characterised by good flexibility and resistance to hydrolysis. Due to their structure, they exhibit better UV stability and a lower tendency to yellowing, which makes them suitable for applications requiring colour fastness.

Aromatic polyester polyols

Aromatic polyester polyols contain aromatic rings in their structure, most often derived from phthalic or terephthalic acid, which translates into high rigidity and thermal resistance of the final materials. They are widely used where mechanical strength and chemical resistance are key.

Production of polyester polyols

The manufacturing process involves combining diols and acids, e.g. glycols with adipic acid or other di-,tricarboxylic reagents, under elevated temperature conditions, often with the removal of water formed in the reaction, which leads to the elongation of the polyester chain and the obtaining of a polyol with a specified hydroxyl character and functionality.

Key chemical parameters

• Hydroxyl functionality: numerous –OH groups allow for controlled reaction with isocyanates and determine the degree of cross-linking and mechanical properties of the resulting polyurethanes.
• Ester structure: –COO– bonds in the polymer chain affect the chemical resistance, hardness and adhesion of polyurethane materials.
• Molar mass: selected, among other things, by the selection of diols and dicarboxylic acids in order to obtain the desired material and processing parameters.

Role in polyurethane chemistry

A significant difference from polyether polyols is the presence of ester bonds in the backbone. Polyester polyols contain primary hydroxyl groups, which makes them less reactive but also more resistant to hydrolysis. Ester segments can improve adhesion and resistance to solvents and chemicals compared to their polyether counterparts.

Applications of polyester polyols

1. Polyurethanes

• Rigid and semi-rigid polyurethane foams,
• Polyurethane elastomers,
• Cast and RIM systems.

2. Coatings, varnishes and paints

• Polyurethane and polyester-urethane coatings,
• Protective and industrial varnishes,
• Chemical and solvent resistant coatings.

3. Adhesives and sealants

• Polyurethane adhesives,
• Construction and industrial sealants,
• Adhesives for wood, metal, plastics and composites.

4. Construction

• Waterproofing systems,
• Polyurethane flooring,
• Construction adhesives and sealants.