Oligo-Polyols for Elastic Polyurethanes

The oligo-polyols for elastic polyurethanes (PU) are characterized by a high molecular weight (MW), usually situated in the range of 2000-6500 daltons, and by a low functionality, of around 2-3 hydroxyl groups/mol. The high elasticity is given firstly by the high mobility of the oligo-polyol chains, which permits free rotation around the bonds of the main chain and, as general rule, these polymers have a low value for the glass transition temperature (Tg) in the range of –50 °C to – 86 °C. At room temperature, the oligo-polyols for elastic PU are situated in the highly elastic domain and conserve this important characteristic at lower temperatures (of course at negative temperatures higher than Tg). It is clear that the high elasticity of the resulting polyurethanes is given by the high MW and high mobility oligo-polyol segment and due to the low crosslink density, as a consequence of the low functionality of the oligo-polyols.

Polyalkylene oxide polyether polyols are the most important group of polyols for PU, representing around 80% of the total oligo-polyols production.

The polyalkylene oxide polyols are obtained by the polymerisation of alkylene oxides, initiated by different polyols called starters or chain initiators. The most important alkylene oxides (oxiranes or epoxides) used in oligo-polyols synthesis are propylene oxide (PO), ethylene oxide (EO) and butylene oxide (BO).

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·        PO homopolymers

·        Block copolymers PO-EO

·        Random copolymers PO-EO (heteropolyethers polyols)

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