FACTORS INFLUENCING THE HYDROPHOBIC RECOVERY OF OXYGEN-PLASMA-TREATED POLYETHYLENE

The hydrophobic recovery of oxygen-plasma-treated hydrophilic surfaces of polyethylene and polypropylene films was investigated by measuring the dependence of the contact angle with the water on the vacuum storage time. It could be shown that the rehydrophobation of the polyethylene surface may be retarded by the previous controlled surface cross-linking in a hydrogen plasma and/or by repeated plasma treatment. However, the loss in hydrophilicity cannot be suppressed for ever. After certain individual periods all treatments lead to the same final state. Nevertheless, in particular, controlled cross-linking seems to be a suitable way for improving the long-term stability of plasma-functionalized polymer surfaces for polymers not tending to chain scission during plasma treatment.