Preparation of adhesive free laminated poly(ethylene terephthalate) films by plasma modification

Abstract

In this research, adhesion free laminated poly(ethylene terephthalate) or PET films were prepared by surface modification of PET film using high temperature pulsed plasma generated from theta-pinch device before compression with metallized PET film at 220°C. In order to determine the optimum condition for the treatment, the number of plasma shot were varied as 5, 10, 15 and 20 shots. In addition, three types of gas including nitrogen, oxygen and argon were used. It was found that the water contact angles of the treated films were lower than 72° of the untreated PET film. Increasing wettability of treated film indicated the formation of hydrophilic groups on the film surface as confirmed by ATR-FTIR. However, when the films were stored for 7 and 14 days, the contact angle increased. Furthermore, plasma treatment did not significantly affect the haze of the films. AFM analysis revealed that after plasma treatment, average roughness of the film surface slightly decreased. It was also found that tensile strength of nitrogen plasma-treated PET films was comparable to that of the untreated film, while those of oxygen and argon plasma-treated PET films slightly decreased. Tensile properties and adhesion strength of plasma-treated laminated films were higher than those of laminated film prepared from the untreated one. Optimum condition for the treatment was to use oxygen plasma at 5 shots in order to achieve the laminated film having overall mechanical properties better than using other conditions.