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| Learning Center Polyol |
No. 2 |
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| Polyether | ||||||||||||||||||||||||||||||||
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No chemistry required (it would not hurt to know some) |
Some chemistry or physics required |
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| Introduction | ||||||||||||||||||||||||||||||||
| Polyols | ||||||||||||||||||||||||||||||||
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Polyols are hydroxyl functional polymers. Depending on the composition they can be polyether or polyester polyols. This indicates that their backbone contains ether or ester groups. Polyether type polyols are the largest group of polyol used in urethanes, they are resistant to alkali (base), low viscous and have low temperature flexibility. Polyethers can have primary (more reactive) or secondary hydroxyl groups (slower reactive). Polyether polyols can have functionality from as low as 2 to as high as 8, depending on what starting polyol was used in their manufacture. Typically they are prepared by reaction of ethylene oxide or propylene oxide with water a starting diol or polyol. Ethylene oxide produces primary hydroxyl functional polyols and propylene oxide predominately secondary hydroxyls. Ethylene oxide containing polyols are lower in viscosity and more water sensitive. Polypropylene glycol is only water soluble at a low molecular weight, only ethylene oxide containing polymers are water soluble at a high MW. If primary hydroxyl functional polymers are desired often propylene oxide is first reacted with the starting polyol and the ethylene oxide is grafted onto the polypropylene oxide polymer. More hydrophobic and polyethers with improved properties are obtained from tetrahydrofuran (THF). |
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