Factors Affecting Vapor-Phase Photografting of Methacrylic Acid on Low-Density Polyethylene Film

Factors affecting photografting (λ > 300 nm) of methacrylic acid on a low-density polyethylene film (thickness = 70 μm) were investigated in a vapor-phase system. Xanthone was coated on the film. Factors examined were pressure of the system (1, 20, and 50 mmHg), polymerization temperature (40, 50, and 60°C), and use of monomer mixed with water. It was found that the grafting rate decreases in the following order: 1 mmHg > 20 mmHg > 50 mmHg at 60°C, and 60°C > 50°C > 40°C under 1 mmHg pressure. The rate was sharply reduced by using monomer mixed with water (monomer/water = 1/1). The contact angle of water on the grafted films largely depended on the grafting conditions, decreasing in the same order as that of the grafting rate described above. Thus, higher wettability was recorded for grafted films prepared under grafting conditions where the grafting rate is slow. The resultant grafted chains are supposed to localize mainly on the film surface.