Scratch behavior of poly(carbonate) film/substrate systems

The effect of adhesion, film thickness and substrate hardness on the scratch behavior of PC film/substrate systems was investigated. Scratch tests were performed using a custom-built scratch tester. The resulting scratches were observed by optical microscopy, atomic force microscopy (AFM), and environmental scanning electron microscopy (ESEM). The critical normal load for delamination/debonding was used as a criterion to determine the scratch resistance of the films. Better film/substrate adhesion or higher film thickness resulted in higher critical loads. The scratch response of PC films depended strongly on the hardness of the substrates on which the films were deposited. Substrates having relatively low hardness (i.e., Al 1100) were severely deformed under the scratching conditions. Intermediate hardness substrates (i.e., Al 6022, Al 6111, and ferroplate) were more resistant to the imposed load; hence, the deformation of the substrates was less severe. High hardness substrates (i.e., glass) resisted the applied load and resulted in higher stress concentration at the interface. Consequently, little or no deformation of these substrates was observed during scratching of PC films on glass substrates.; Influence of gamma-aminopropyltriethoxysilane (gamma-APS) on the scratch behavior of PC films was determined. The critical load of PC films increased rapidly as the concentration of the solutions used to deposit the gamma-APS films increased from 0.0 to 0.2%; thereafter, the critical load increased only slightly as concentration of the gamma-APS solutions increased from 0.2 to 5%. Reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS) were used to examine the chemical reaction at gamma-APS/PC interface using diphenyl carbonate (DPC) model compound. RAIR results revealed the formation of urethane and urea linkages between gamma-APS and DPC. Curve fitting of high resolution C1s spectra showed that the main reaction product between DPC and 0.2% gamma-APS was urethanes. Heat treatment of 0.2% gamma-APS films resulted in lower critical loads due to higher crosslink structure of the primer. Therefore, diffusion of PC into gamma-APS primer was limited. High reaction temperature for gamma-APS and PC caused oxidation of amine, however, it increased the probability of amine to react to carbonate due to increasing mobility of PC chains.