Surface graft copolymerization of acrylic acid onto LDPE film through corona discharge

In this work the corona discharge technique was explored as a means of forming chemically active sites onto the low density polyethylene (LDPE) film surface. The active species thus prepared at atmospheric pressure in air is exploited to induce simultaneously copolymerization of acrylic acid (AA) onto LDPE film in aqueous solution. The results show that with the corona discharge treatment time, treatment voltage and inhibitor concentration in reaction solution, the grafting degree increases, but decreases after passing a maximum. As the reaction time, temperature and AA concentration in reaction solution increase, the grafting degree increases. Under the condition of 20% by volume AA concentration, 70°C copolymerization temperature and 1.5 h reaction time, the grafting degree of LDPE film after treated 72 s reaches a quite high value of 220.55 μg cm−2. Some characteristic peaks of the grafted LDPE come into view at 1574 cm−1 on ATR-IR spectra (>CO in –COONa group on the grafted LDPE film surface neutralized with NaOH) and at 531 eV on ESCA spectra (O1s), their intensities increase with grafting degree. The hydrophilicity and the peel strength of grafted LDPE film are improved remarkably as compared with that of the ungrafted LDPE film.