General polyurethane adhesive is not resistant to high temperature, this is not resistant to high temperature refers to pure crushing is not resistant to high temperature, do not understand as not resistant to damp heat, not resistant to damp heat simple understanding is not resistant to high temperature and water collectively! Why is polyurethane adhesive not resistant to high temperature? Let's listen to Xiaobian's explanation!
Here, we explain it in terms of group fracture. Specifically speaking, it is mainly to decompose C-N bond. The bond energy is low, only 69.7, much lower than C-C! N-H and C = O bond energy are both high! The specific bond energy can be converted to the corresponding thermal decomposition temperature. Bond hydrolysis mainly refers to the ester bond on polyester, not nhco. This is not called ester bond, but ammonia ester bond! The latter is more resistant to hydrolysis than the former! If there are polyester polyols in the polyurethane adhesive, and then the polyol reacts with NCO to form polyurethane, then there are two ester bonds in the adhesive polymer. Generally speaking, hydrolysis refers to the ester bond hydrolysis of the polyester polyol prepared by condensation.
The quality of the hydrolytic resistance of a polyester is mainly determined by the number of ester bonds contained in the single polyester unit structure. The other factors are only the auxiliary factors, not the decisive factors.