Enhancement of surface properties on Low Density Polyethylene packaging films using various fluorination routes

Nowadays, packaging market deployment requires an important attention. Influence of treatment with molecular (F-2) or atomic (F-) fluorine on properties of Low Density Polyethylene (LDPE) films was investigated. The films were treated using direct fluorination conditions with F-2 or a specific reagent XeF2, which releases atomic fluorine F. Changes of LDPE chemical composition were investigated by FUR and solid state NMR. Surface morphology was studied by several microscopy techniques (SEM and AN). Finally to further characterize film properties after treatments, surface energy measurements and electron paramagnetic resonance (EPR) analyses were also carried out. An upper fluorinated layer, which contains mainly high amount of -CF2-, was formed during the direct fluorination conditions (F-2). For the process performed with XeF2, specific groups -CHF- were detected not only on the polymer surface but also in the bulk. The final CHF/CF2 ratio depended on the fluorination route. Treatment with F. (originated from XeF2 decomposition) resulted in -CHF- groups in bulk prevailing formation whereas F-2 formed mainly -CF2- groups. Regardless to the reactive species, radicals (dangling bonds) appeared during the fluorination and reacted with oxygen during the exposition to air after the treatment. Such a process resulted in oxygenated polar groups formation and consequently in the surface energy increase. (C) 2015 Elsevier Ltd. All rights reserved.