POSS-modified UV-curable coatings with improved scratch hardness and hydrophobicity

The work is devoted to modification of UV-curable coatings with mixtures of POSS functionalized with octa(methacryloxy) (8M-POSS) or octa(fluoroalkyl) (8F-POSS) substituents. Two types of coatings were formulated: for wood-derived substrate and for aluminum substrate. Modification with POSS mixtures leads to a synergistic effect: the improvement of the hydrophobicity of the coating surface and its scratch hardness by POSS mixtures is better than by individual POSS derivatives. The observed increase in the contact angle results probably from the enhanced surface roughness caused by 8M-POSS aggregates and is further enhanced by hydrophobic properties of POSS functionalized with fluoroalkyl substituents. The improvement of the scratch resistance is associated mainly with the formation of a sliding layer arising by diffusion of 8F-POSS molecules to the coating surface. The significant increase of the surface hydrophobicity (by 60%) and scratch hardness (even by 400%) is obtained using only small amounts (1.5-3 wt %) of the investigated POSS compounds.