Adipate polyester polyol
Polyester polyols trade some hydrolysis resistance for toughness, adhesion and resistance to oils and solvents, which makes them a staple of industrial polyurethanes.
Polyester polyols are made by condensing a diacid (such as adipic or phthalic acid) with diols or triols (such as ethylene glycol, butanediol, neopentyl glycol or trimethylolpropane), using excess alcohol so the chains end in hydroxyl groups. Because the recipe varies so widely, there is no single CAS number; each product is defined by its acid, glycols, OH number and functionality.
Polyester polyols are used in industrial and maintenance polyurethane coatings, coil and wood finishes, adhesives and oil-resistant elastomers. Aromatic acids add hardness and chemical resistance; aliphatic acids such as adipic give flexibility.
Ester linkages are polar and pack well, giving strong intermolecular forces, good adhesion and resistance to oils and many solvents. The trade-off is hydrolysis: esters can break down under hot, wet or alkaline conditions, which is why polyethers are preferred for wet service.
Most polyester polyols are low-hazard. Keep them dry, since absorbed water reacts with isocyanates, and warm viscous grades gently before use.
They are more prone to hydrolysis than polyethers, especially when hot or alkaline. For immersion and wet service, polyether-based or specially formulated hydrolysis-resistant polyesters are preferred.
A measure of residual carboxylic acid groups. Low acid number is preferred because acid groups can affect catalysis and hydrolytic stability.
