Polyurethane (PUR and PU) is a polymer composed of organic units joined by carbamate (urethane) links. While most polyurethanes are thermosetting polymers that do not melt when heated, thermoplastic polyurethanes are also available. Polyurethane polymers are traditionally and most commonly formed by reacting a di- or polyisocyanate with a polyol. Both the isocyanates and polyols used to make polyurethanes contain, on average, two or more functional groups per molecule.
Beside isocyanate, the other reacting species required to produce polyurethanes are compounds that contain multiple alcohol groups (OH), called polyols. Materials often used for this purpose are polyether polyols, which are polymers formed from cyclic ethers. They are typically produced through an alkylene oxide polymerization process. They are high molecular weight polymers that have a wide range of viscosity. Various polyether polyols that are used include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These materials are generally utilized when the desired polyurethane is going to be used to make flexible foams or thermoset elastomers.
Polyester polyols may also be used as a reacting species in the production of polyurethanes. They can be obtained as a byproduct of terephthalic acid production. They are typically based on saturated aromatic carboxylic acids and diols. Branched polyester polyols are used for polyurethane foams and coatings. Polyester polyols were the most used reacting species for the production of polyurethanes. However, polyether polyols became significantly less expense and have supplanted polyester polyols.
Polyether polyols were cheaper, easier to handle and more water-resistant than polyester polyols, and became more popular. The availability inexpensive polyether polyols, and poly-methylene diphenyl diisocyanate (P-MDI example) allowed polyurethane rigid foams to be used as high-performance insulation materials.
Hope this will help.
TD
Both. There are also oleochemical polyols (having fully hydrocarbon backbones), such as soybean-oil polyols, that are widely used now for rigid PU foams. The choice of a polyol component for commercial applications depends on many features such as cost (PEs>PEth>NOP), mechanical properties (hardness, compression strength), performance features (e.g. for low- or high-temperature insulation), hydrolytic resistance and biostability (NOP>PEth>PEs), chemical resistance, and so on.
If you would like to learn more about the topic, I recommend that you read a comprehensive M. Ionescu's book entitled "Chemistry and Technology of Polyols for Polyurethanes" (2005, Rapra Technology).
Polyurethane (PUR and PU) is a polymer composed of organic units joined by carbamate (urethane) links. While most polyurethanes are thermosetting polymers that do not melt when heated, thermoplastic polyurethanes are also available. Polyurethane polymers are traditionally and most commonly formed by reacting a di- or polyisocyanate with a polyol. Both the isocyanates and polyols used to make polyurethanes contain, on average, two or more functional groups per molecule.
Beside isocyanate, the other reacting species required to produce polyurethanes are compounds that contain multiple alcohol groups (OH), called polyols. Materials often used for this purpose are polyether polyols, which are polymers formed from cyclic ethers. They are typically produced through an alkylene oxide polymerization process. They are high molecular weight polymers that have a wide range of viscosity. Various polyether polyols that are used include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These materials are generally utilized when the desired polyurethane is going to be used to make flexible foams or thermoset elastomers.
Polyester polyols may also be used as a reacting species in the production of polyurethanes. They can be obtained as a byproduct of terephthalic acid production. They are typically based on saturated aromatic carboxylic acids and diols. Branched polyester polyols are used for polyurethane foams and coatings. Polyester polyols were the most used reacting species for the production of polyurethanes. However, polyether polyols became significantly less expense and have supplanted polyester polyols.
Polyether polyols were cheaper, easier to handle and more water-resistant than polyester polyols, and became more popular. The availability inexpensive polyether polyols, and poly-methylene diphenyl diisocyanate (P-MDI example) allowed polyurethane rigid foams to be used as high-performance insulation materials.
Hope this will help.
TD
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