Plasma and chromic acid treatments of polycarbonate surface to improve coating-substrate adhesion

摘要

The influence of Ar/O_2 plasma activation and chromic acid etching of polycarbonate (PC) surface on the adhesion of coating to substrate was systematically studied by cross-cut and tape peel methods through temperature-shock aging tests. The differences between the wettabilities and elemental compositions of plasma-treated and chromic acid-treated PC surfaces prior to coating deposition were evaluated by contact angle measurements and X-ray photoelectron spectroscopy. To elucidate the adhesion failure of the coatings, nanoindentation technique was employed for the quantitative assessment of the nanomechanical changes of coating depositions on PCs after temperature-shock aging tests. The two surface treatments can significantly improve the hydrophilicity and polarity of the PC surface, resulting in excellent adhesion of the coating on the PC substrate. Temperature-shock aging tests reveal that the adhesion of coating on plasma-modified substrates is superior to that of chromic acid-etched substrates. We propose that the improved adhesion of the coating on the plasma-modified PC can be attributed to the higher wettability and more cross-linking of C-O-Si bonds at the coating-substrate interface.