Polyester polyols

In the production of polyester polyols, a distinction is made between synthetic polyesters and modified, vegetable esters. ISO-ELEKTRA offers you selected castor oil-based polyester polyols such as ketone resin-modified polyols.

Classic petrochemical polyester polyols are produced by the condensation reaction of organic dicarboxylic acids and difunctional alcohols. The alcohol must be present in excess in order to obtain polyester polyols with the required hydroxyl groups.

Important starting products are the dicarboxylic acids adipic, succinic and phthalic acid and ethylene glycols or propylene glycols for the alcohol component. There are a number of other acids and alcohols that can also be used – possibly also as co-reactants.

Polyester polyols are usually present at room temperature as highly viscous liquids, sometimes also as solids. Due to their ester bond, they are more sensitive to hydrolysis than polyether polyols. However, the hydrophobic properties of polyester polyols, which increase with increasing chain length, counteract the sensitivity to hydrolysis.

Although polyester polyols tend to harden and become brittle at low temperatures, they are much more resistant to light, thermal ageing and oxidative processes than polyether polyols. In many cases, plastics based on polyester urethanes exhibit a very high level of tear resistance and tear propagation resistance.

Castor oil is the only naturally occurring oil with hydroxyl groups, which is why it can be used for the production of polyurethane-based plastics without chemical modification. The extraction of castor oil is significantly more energy-efficient than that of petrochemical products. During the growth phase, the plants extract carbon dioxide from the atmosphere, which can be incorporated into the polymer. This means that the use of castor oil in the cast resin sector can have a negative, advantageous CO2 balance.

The modification with ketone resins in particular has proven itself for resistant polyurethane casting resins, coatings and adhesives, which we offer in the same way as tried and tested blends with synthetic polyols.