Described herein is a method of making a multi-layer article and paint protective films, wherein a mixture comprising a polyurethane coating solution and a plurality of nanoparticles is coated onto a casting liner to form a first layer; and a thermoplastic polyurethane is disposed onto the first layer opposite the casting liner. Multi-layer articles by the process of the present disclosure have been found to be resistant to compositions comprising strong acids and/or a functionalized organosilane.