Synthesis and characterization of grafted polyethylenes for use as membranes in water desalination

Abstract

Polyethylene, although known to have very poor permeability behaviour towards electrolyte solution, functionalization through grafting is found to improve upon this property. Grafting of vinyl monomers containing polar pendant groups such as - CN of pyridine, - CN of methacrylonitrile, -COOR of esters of acrylic acid, can impart desirable properties to the hydrophobic backbone. In the present work, grafting of 4-vinyl pyridine (4-VP) and a binary mixture of 4-VP and methacrylonitrile (4-VP + MAN) onto PE film has been carried out by radiochemical method. Optimum conditions for affording maximum percentage of grafting have been evaluated. The grafted polyethylene membranes have been characterized by IR spectroscopy, scanning electron microscopy, thermogravimetric analysis, swelling behaviour, percent area change and permeability behaviour. Thermal stability of the grafted PE film was found to decrease upon grafting. However, at higher temperature ranges corresponding to the weight loss above 80%, thermal stability of PE film and PE grafted with mixed monomer becomes almost equal. Percent area change upon grafting and percent swelling in different solvents were found to increase in grafted films. The grafted membranes showed significant permeability towards electrolyte solution and were capable of effecting desalination of brine solution.