Surface craft copolymerization of 2-hydroxyethyl methacrylate onto low-density polyethylene film through corona discharge in air

The corona discharge technique was explored as a means of forming chemically active sites on a low-density polyethylene (LDPE) film surface. The active species thus prepared at atmospheric pressure in air was exploited to subsequently induce copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto LDPE film in aqueous solution. The results showed that with the corona discharge voltage, reaction temperature, and inhibitor concentration in the reaction solution the grafting degree increased to a maximum and then decreased. As the corona discharge time, reaction time, and HEMA concentration in the reaction solution increased, the grafting degree increased. With reaction conditions of a 5 vol % HEMA concentration, 50 degreesC copolymerization temperature, and a 2.0-h reaction time, the degree of grafting of the LDPE film reached a high value of 158.0 mug/cm(2) after treatment for 72 s with a 15-kV voltage at 50 Hz. Some characteristic peaks of the grafted LDPE came into view at 1719 cm-l on attenuated total reflectance IR spectra (> C=O in ester groups) and at 531 eV on electron spectroscopy for chemical analysis (ESCA) spectra (O-1s). The C-1s core level ESCA spectrum of HEMA-grafted LDPE showed two strong peaks at similar to 286.6 eV (-(C) under bar -O- from hydroxyl groups and ester groups) and similar to 289.1 eV (O=(C) under bar -O- from ester groups), and the C atom ratio in the -C-O- groups and O=C-O groups was 2:1. The hydrophilicity of the grafted LDPE film was remarkably improved compared to that of the ungrafted LDPE film. (C) 2001 John Wiley & Sons, Inc.