Characterization of metallized biaxially oriented polypropylene film

The effect of corona unit energy applied for retreatment of metallized biaxially oriented polypropylene film surfaces before the lamination process was studied using optical, scanning electron, and atomic force microscopies. Increased surface roughness and polarity due to oxygen groups were detected, and these changes became more evident with the increase of corona treatment intensity. The number and size of spots on the surface, possibly deriving from processing aids incorporated as additives into the polymer, increase with corona treatment. The response of specimens in accelerated aging was also studied for evaluation of the outdoor stability of these composite structures. Specimens were exposed to the combined action of UV-radiation, humidity, and heat, and the stability of yellow, orange-yellow, orange, green, and bordeaux colors was determined as a function of the exposure time. Minor color changes were recorded for exposure up to 100 h, which became more significant for longer exposure intervals depending on the type of color. Finally, a 40% decrease in tensile strength was observed after 216 h of ageing, accompanied with a decrease of 15%, of modulus and an increase of 160% in the elongation at break, possibly because of the plasticizing effect taking place during the ageing process. (c) 2007 Wiley Periodicals, Inc.