Solventless Surface Modification of LDPE through Electron Beam Radiation Grafting of 2-Hydroxyethyl Methacrylate

The electron beam radiation technique has been explored as the latest and most effective means of forming chemically active sites on LDPE surface. In this novel work a solventless grafting of 2-hydroxyethyl methacrylate (HEMA) on to LDPE surface was conducted. Thus prepared active sites were exploited to subsequently solvent-less graft copolymerization of HEMA onto LDPE by high energy electron beam radiation (10 MeV) at dose range of 10 up to 200 kGy at atmospheric pressure in air. As HEMA could not wet LDPE surface, its synthesized tacky polymer was used for coating and then grafting purposes. LDPE film and sheet surfaces were impregnated with the prepared adhesive and were irradiated. FTIR Spectra showed that the concentration of characteristic bonds of poly(HEMA-g-LDPE) (C=0 in ester groups, in hydroxyl groups as C-OH, and ether carbon bonds as C-0) increased with increasing irradiation dose, also, the percentage of grafting significantly increased up to 60%. The hydrophilicity of the grafted surface considerably increased compared to that of the ungrafted ones as contact angle measurements showed a 72% decrease. Furthermore, the yields of gel content measurement were investigated and the topology of the surface and cross-section of poly(HEMAg-LDPE) films and sheets was studied by means of SEM. Moreover, the mechanism of achieving up to 70% cross-linked network in solid semi-crystalline LDPE is discussed.