Layer by layer nanoarchitectures for the surface protection of polycarbonate

The layer by layer (LbL) technique has been exploited for depositing a completely inorganic silica coating on 0.2 and 1 mm thick polycarbonate (PC) films. The modification of the surface of the polymer substrate has been assessed by contact angle measurements, SEM and FT-IR analyses. The flammability and combustion behaviour of the LbL-treated films have also been investigated: surprisingly, the coatings deposited on 0.2 mm PC films have suppressed the incandescent melt dripping during the flammability tests. Furthermore, cone calorimetry tests have shown a great enhancement of the flame retardancy properties of PC, after the LbL treatment. On the other hand, a significant decrease of the performances of 1 mm coated substrates has been observed and ascribed to the too low surface-to-bulk ratio and to the poor coating stability during the combustion, as revealed by SEM analysis.