The quest for improved scratch/abrasion-resistant coatings is a goal for many coatings formulators. Thousands of scratch-resistant coating applications are present in our everyday lives. Examples of these applications include coatings for wood floors, safety glasses, electronic displays, automotive finishes and polycarbonate panels. Improving the mar, scratch and/or abrasion in these transparent coating applications is a major challenge, particularly with regard to not affecting the other performance attributes of the coating.
Incorporation of inorganic fillers into coatings to improve mechanical properties is well known. Drawbacks associated with this approach can include loss of transparency, reduced coating flexibility, loss of impact resistance, increase in coating viscosity and appearance of defects. To overcome these defects, a filler material should impart improved scratch resistance without causing the aforementioned detriments. Nanomaterials have the potential to overcome many of these detriments because of their inherent small size and particle morphology. Maintaining transparency in a coating containing inorganic filler particles is a challenge. Four properties dictate the degree of transparency in a composite material: film thickness, filler concentration, filler particle size, and the difference in refractive index between the bulk coating and the filler particle.