Photografting of Methacrylic Acid onto HDPE Initiated by Acetaldehyde in Aqueous Solutions

Acetaldehyde could act as a very effective photoinitiator for water-borne photografting. The photografting of methacrylic acid (MAA) onto polyethylene initiated by acetaldehyde in aqueous solutions was reported. Acetaldehyde had higher photoinitiation efficiency than acetone and formaldehyde. The extent of grafting varied with the acetaldehyde content in the solution and it showed the maximum when the content of acetaldehyde was about 10 w/w %. The extent of grafting firstly increased with the increase of monomer concentration till 2 mol/L and then kept constant or slightly decreased. ATR-FTIR characterizations of the grafted samples proved the successful grafting of MAA onto PE, and the calculated carbonyl indexes were in accord with the results obtained by the gravimetric method. The water absorbency of the grafted samples increased almost linearly with the extent of grafting. The difference in the photoinitiation efficiencies of acetaldehyde, acetone and formaldehyde was discussed through their differences in the n-pi* transitions in water and the photoinitiation process. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 629-635, 2011