Studies on photografting of triemethylol propane triacrylate onto the surface of LDPE films

Photografting (lambda> 300 nm) of trimethylol propane triacrylate (TMPTA) onto the surface of low-density polyethylene (LDPE) films was investigated at room temperature in a mixed solvent composed of acetone and water, using benzophenone ( BP) as an initiator. It seems that the polyfunctional monomer could be grafted easily onto the surface,forming a cross-linked structure, and as confirmed by IR spectroscopy there were still some double bonds un-reacted. Influences on the photografting of TMPTA were examined and the experimental results indicated that longer irradiation time and higher monomer concentration were useful for the increase of grafted polymer conversion. At a certain concentration of BP, a maximum grafted polymer conversion was obtained, and the decrease of grafted conversion at higher BP concentrations was probably due to the absorption effect of initiator. The increase of grafted polymer conversion was observed with increasing the water contents. SEM images showed that a lot of small particles appeared on the surface of grafted films, and water contact angle measurements noted that the surface hydrophobicity was improved.