GRAFTING OF MALEIC ANHYDRIDE TO POLYETHYLENE (REVIEW)

This review aims to summarize the current knowledge on the synthesis of graft copolymers of polyolefins with polar oxygen-containing unsaturated monomers by the free radical chain process. The issues of using these graft copolymers are touched upon. A comparison was made of the effectiveness of various technological methods for carrying out the grafting process. More attention is paid to the graft copolymer of polyethylene with maleic anhydride, obtained by reactive extrusion in a polymer melt. The main chemical reactions occurring during the radical chain graft copolymerization of polyethylene with maleic anhydride are considered. The main subject of discussion is the relationship between the production conditions and the degree of grafting of maleic anhydride to polyethylene and the volume of adverse reactions. The influence of synthesis technology, the concentration and nature of the initiator and polar monomer, temperature, pressure and process duration, extruder screw design and mixing efficiency, the presence and nature of grafting coagents on the concentration of the grafted monomer and on side reactions is discussed. The main initiators of the free radical grafting process are considered, and rational approaches to their selection are discussed. The effectiveness of various classes of process co-agents in increasing the degree of grafting of the polar monomer to the polyolefin and reducing the volume of side undesirable reactions, such as cross-linking and destruction of the polyolefin, homopolymerization of the polar monomer, has been analyzed. Possible options for the structure of graft copolymers of polyolefins with polar monomers are considered. At the end of the review, a brief analysis of patents relating to the grafting of maleic anhydride to polyethylene and copolymers of ethylene with α-olefins under conditions of mixing the polyolefin melt in an extruder is provided.