FREE-RADICAL GRAFT-COPOLYMERIZATION OF POLAR MONOMERS ON LOW-DENSITY POLYETHYLENE UNDER MELT-PROCESSING CONDITIONS

Free-radical graft copolymerization of acrylic acid and ethyl methacry late on low-density polyethylene (LDPE) was studied under simulated me lt-processing conditions. Initiators benzoyl peroxide and dicumyl pero xide were evaluated for their grafting efficiency. Benzoyl peroxide wa s found to be an excellent catalyst for the grafting of both monomers, whereas dicumyl peroxide was quite ineffective. Effect of reaction ti me, initiator concentration, and reaction temperature was studied for benzoyl peroxide initiated graft copolymerization of the two monomers. The changes in the torque and temperature of the reaction melt in the course of the reaction were recorded. More or less quantitative graft ing of both monomers could be achieved, using low initiator concentrat ions, in very short reaction times. The possibility of modifying LDPE during melt extrusion in the extruder itself has been clearly demonstr ated. This would be a highly cost-effective way of diversifying the pr operties and applications of LDPE. Crosslinking was found to be relati vely higher in the graft copolymerization of acrylic acid but within a cceptable limits. Possible mechanisms of this are discussed.