Functionalization of polyethylene film by radiochemical grafting for use as membranes in seawater desalination

Functionalization of polyethylene (PE) film with vinyl monomers containing polar groups can impart certain important additional properties to polyethylene membranes. With this idea in mind, attempts have been made to incorporate functional groups such as nitrile and ester groups onto polyethylene film by grafting methacrylonitrile (MAN) and a binary mixture of MAN and methylacrylate (MA) by radiochemical method. Optimum conditions for affording maximum percentage of grafting (Pg) have been evaluated. The grafted membranes have been characterized by IR spectroscopy and by thermogravimetric analysis. Thermal stability of the grafted PE films was found to decrease to some extent upon grafting. Percent area change and percent swelling of the grafted films in polar and nonpolar solvents have been determined. The dimension of the grafted films enhanced with increasing level of grafting indicating that grafting is not only confined to surface of the film but also proceeds into the interior of the film. Desalination of a model brine solution has been qualitatively studied using PE-g-poly(MAN) and PE-g-poly(MAN-co-MA) membranes. The grafted films were capable of effecting desalination of model brine solutions with enhanced permeability as compared to ungrafted PE film.