Aqueous wet coatings for transparent plastic glazing

Electrostatically stabilized particulate sols, e.g. aqueous silica or alumi na sols, have been surface-modified to reduce the particle/particle interac tion and to obtain electrosterically stabilized sols. Epoxy functionalized alkoxysilanes were used as surface modifiers for alumina, silica or zirconi a particles to achieve water dispersible nanoparticulate coating materials. After evaporating the organic solvent (produced by hydrolysis and condensa tion) aqueous sol-gel coatings have been prepared with organic solvent cont ents below 5%. The storage stability of these materials has been investigat ed by Si-29-NMR. An amino functionalized alkoxysilane was used as condensat ion catalyst and the nanocomposite material was thermally cured at 130 degr ees C after flow or spray coating on pretreated polycarbonate substrates. T he coatings show excellent adhesion which was shown by cross cut and tape t est. After 1000 cycles Taber abrasion test (CS-10F, 500 g, DIN 52347) losse s of transmittance due to scattering of 2-6% were achieved with a coating t hickness of about 5 mu m. (C) 1999 Published by Elsevier Science S.A. All r ights reserved.