We have all encountered very hard, highly crosslinked, mechanically strong coating systems that have a major disadvantage: Under impact, they are inflexible and brittle, resulting in deformations and spalling. The remaining unprotected substrate no longer satisfies optical aspects and other essential usage criteria, necessitating replacement or repair of the damaged object.
Incorporating flexible constituents in a highly crosslinked binder matrix results in markedly improved impact strength but a lower degree of crosslinking. This weakens the network density of the system as well as the surface hardness and chemical resistance. Combination with a second microphase, such as dispersed rubber or thermoplastics, can lead to significantly improved toughness. In this type of in-situ generation of particles, however, it is extremely difficult to control the particle size without fundamentally altering the properties of the polymer matrix.1