Method of providing a polycarbonate article with a uniform and durable silica filled organopolysiloxane coating

A method for providing a uniform and durably adhered mar, scratch, abrasion and chemical solvent resistant colloidal silica filled organopolysiloxane coating on a polycarbonate article which comprises:

• (i) applying onto the surface of a polycarbonate substrate a primer emulsion composition consisting essentially of, in percent by weight, (a) from about 1 to about 10 percent of a thermosettable acrylic polymer, (b) from about 1 to about 10 percent of at least one ultraviolet light screening compound selected from the class consisting of benzylidene malonates and cyanoacrylates, (c) from 20 to about 40 percent of a hydroxy ether or an alkanol containing from 1 to 4 carbon atoms, and (d) from about 40 to about 78 percent water;
• (ii) evaporating off a substantial portion of said water and hydroxy ether or alkanol from said primer emulsion composition thereby forming a layer comprised of said thermosettable acrylic polymer and at least one of said ultraviolet light screening compounds;
• (iii) applying heat to said layer at a temperature and for a period of time effective to cure said thermosettable acrylic polymer;
• (iv) applying onto said cured primer layer a colloidal silica filled further curable organopolysiloxane top coat composition comprising a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of a silanol of the formula RSi(OH).sub.3 wherein R is an alkyl radical containing 1 to 3 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, at least 70 weight percent of said silanol being CH.sub.3 Si(OH).sub.3, said composition containing sufficient acid to provide a pH in the range of 3.0 to 6.0;
• (v) evaporating off a substantial portion of the volatile solvents from said top coat composition thereby forming a layer comprised of a colloidal silica filled partial condensate of said silanol;
• and,
• (vi) thermally curing said colloidal silica filled partial condensate of said silanol.