GRAFT-POLYMERIZATION OF ACRYLIC-ACID ONTO POLYETHYLENE FILM BY PRE-IRRADIATION METHOD .1. EFFECTS OF PRE-IRRADIATION DOSE, MONOMER CONCENTRATION, REACTION TEMPERATURE, AND FILM THICKNESS

In the reported experiments, low- and high-density polyethylenes were irradiated by electron beams with dose of 2-50 Mrad and then immersed in aqueous solution of acrylic acid (monomer concentration from 30 to 100 wt %) for 10 min-5 h at a temperature of 25-40 degree C. The degree of grafting increases with time and levels off. High density polyethylene shows lower grafting rate and higher final % grafting in compared with low-density polyethylene. Both grafting rate and final % grafting increase with total dose of preirradiation, but show some saturation at high doses. The highest grafting rate was observed at 60 wt % of monomer concentration where the grafted polyethylene swells to the largest extent in the monomer mixture. Apparent activation energies for the grafting are 19. 6 and 27. 3 kcal/mol for low- and high-density polyethylenes, respectively, reflecting the process of monomer diffusion in the film. Grafting rate decreases with increasing film thickness. Graft polymerization starts on the surface of the film and proceeds to the inner part with monomer diffusion through the grafted layer.