Background & Method: The incorporation of methacrylate capped zirconia nanocrystal (MZN) into an acrylic resin produced a UV curable hard-coat. The vinylfunctionalized surface of the nanoparticle improved its compatibility with the acrylate matrix, thus enabled an excellent dispersion even at 54 wt% zirconia leading to a transparent coating thicker than ten micrometers. The addition of nano-filler further improved the thermal stability and the mechanical strength of the composite. The thermal degradation temperature of the composite moved up by more than 100oC without altering the glass transition temperature. The nanoindentation hardness and the reduced modulus increased from 173 MPa and 1.36 GPa for the pure resin to 478 MPa and 6.7 GPa, respectively, for the composite film with 54 wt% zirconia.
Results: The composite films showed a roughly linear increase of the refractive index with the volume fraction of zirconia. At 54 wt% loading, the index reached 1.6388.
Conclusion: Furthermore, the transparent sol formed by dispersing MZN powder in a solvent also produced a transparent film on PMMA. However, the high inorganic content introduced some porosity into the film and made it vulnerable to creep and abrasion thus unsuitable for hard-coat.