Improved adhesion of PMSQ hard coatings on polymer substrates

Various surface treatment methods were investigated to improve the adhesion of abrasion-resistant polymethylsilsesquioxane (PMSQ) coatings on the optical resins. The adhesion of PMSQ films was improved on polymethylmethacrylate (PMMA), polycarbonate (PC), and PC/acrylonitrile butadiene styrene (ABS) by pretreating their surface with O₂ plasma or chromic acid followed by surface grafting with trimethyl ethoxysilane (TMES). After the O₂ plasma and the subsequent TMES treatments, the adhesion of PMSQ coating on PMMA substrate was significantly enhanced by the reduction of the percentage of peeling area from ~100% to <1% in cross cut tests. After the chromic acid and the subsequent TMES treatments of PC and PC/ABS substrates, the adhesion of PMSQ coatings was also significantly enhanced by reducing the percentages of peeling areas from nearly 100% to 50% and <1%, respectively, for PC and PC/ABS. The PMSQ coating might increase the hardness of the polymer by two to three levels.