Лако-красочные материалы — производство

Flexibility may be improved by using amine compounds as hardeners. Flexibilization and an increase in impact toughness are also obtained by incorporating suitable polymers on the epoxy resin side. Whilst flexibilizers are incorporated into the epoxy matrix and decrease the Tg-values, polymer modifiers that improve impact toughness

are in solution with the epoxy resin from the outset, and then form separate polymer phases during the crosslinking process. Although having only a slight influence on Tg, they confer an increased impact bending strength to the epoxy resins, yielding adhesive systems that are crash-resistant under dynamic loads. Modifiers that increase impact toughness are added at a rate of 15-20% in relation to the total formulation. Polypropylene glycol diglycidyl ether is an example of a flexibilizing epoxy resin. Usually, flexibilizers of epoxy resin adhesives are added to the hardener part, while modifiers of impact toughness are added to the resin part (e. g. acryloni­trile-butadiene copolymers provided with carboxyl groups). In order to ensure their compatibility with the epoxy resin, these copolymers are reacted with an excess of epoxy resins.

The impact toughness can also be improved by adding core-shell particles. The core consists of elastomers (e. g. polybutadienes, polyacrylates or polysiloxanes) with a low Tg-value, and is coated with a thin layer of crosslinked polyacrylates. Core-shell particles have the advantage of having a defined particle size ranging between 0.1 and 100 pm.