16 сентября, 2015 
Pokraskin The most widely used polyols employed in polyurethane adhesives are mainly polyether polyols and polyester polyols. The synthesis of polyether polyols takes place via a ring-opening polymerization of ethylene, propylene or butylene oxides, respectively, with an initiator in the presence of a strong base.
Polyether polyols can be obtained with different functionalities, molecular weights and hydrophobic characteristics, respectively, by means of specific procedures of synthesis. The most important properties of polyether diols are their low viscosity, good flexibility at low temperatures, and their resistance to alkaline hydrolysis. Polyester polyols are usually generated by a reaction of adipic acid with different glycols. Compared to polyether polyols, polyester polyols have a higher tensile strength and a higher resistance to heat.
Tertiary amines, such as triethylamine, N-methyl-morpholine and triethylene diamine, or metal salts such as tributyltin acetate and dibutyltin dilaurate, are used to accelerate the reaction of isocyanates with nucleophilies [29-31]. Tin compounds have a higher catalytic activity than tertiary amines [33].
Опубликовано в рубрике 