Лако-красочные материалы — производство

A distinctive feature of the polymer structure of polyurethane adhesives is the presence of hard and soft segments. Soft segments formed by long-chain poly­ether polyols have a low Tg; at room temperature they are in the entropy-elastic dispersion range. Hard segments are created by the crosslinking of diisocyanates with short-chain diols or diamines. Hard segments associate with each other to generate regions with high Tg-values, sometimes even leading to crystallization, thereby making it possible to generate polyurethane adhesives with two different Tg-values.

While it is possible to generate adhesives with a wide variety of mechanical material properties, it is not easy to separate the properties and application fields of polyurethane adhesives from those of other adhesive systems. Generally, the Tg of polyurethanes is higher than that of silicones, but lower than that of highly cross — linked, structural epoxy resin adhesives; hence, polyurethane adhesives also have other mechanical material properties compared to these adhesive systems. Polyur­ethanes can be subdivided into either one-part or two-part systems.