Surface modification of low density polyethylene films by homogeneous catalytic ozonation

▸ Surfaces of low density polyethylene films were modified to increase hydrophilicity by ozonation. ▸ A novel approach, aqueous ozonation with a homogeneous catalyst, FeCl3, was proved successful. ▸ Effects of operating parameters on peroxide generation were investigated. Low density polyethylene films were treated by ozone to generate peroxides on the surfaces. The peroxides generated are capable of initiating radical graft polymerization of hydrophilic vinyl monomers onto the polymers, resulting in hydrophilic surfaces. Results of ozonation revealed that molecular ozone instead of hydroxyl radicals was the main oxidant for peroxide generation. A novel approach, aqueous ozonation with the addition of a soluble transitional metal salt, FeCl3, as a homogeneous catalyst, was proposed and proved to be successful in this study. The addition of FeCl3 could increase peroxide generation by 22.7%, compared to its non-catalyzed counterpart. An optimum catalyst concentration, 0.04g/L, was determined. Also, the effects of pH, ozonation time and applied ozone dose on peroxide generation were investigated. The loss in tensile strength of the films would be 15% or less if the applied ozone dose was not over 2wt.%. The functional groups generated on the film surfaces were characterized by FTIR, the contact angle and surface roughness of the film were also examined before and after ozonation.