Preparation method of multi-graft monomer polylactic acid-based graft copolymer

The invention relates to a preparation method of a copolymer, in particular to a preparation method of a multi-graft-monomer polylactic acid-based graft copolymer. The graft copolymer is prepared from the following raw materials: 100 parts of polylactic acid; 0-10 parts of a grafting monomer; 0-10 parts of an auxiliary grafting monomer; and 0-5 parts of an initiator. The preparation method comprises the following steps: carrying out melt grafting on the polylactic acid, the two grafting monomers, the auxiliary grafting monomer and the initiator to prepare the grafted copolymer. The compatibility of a polylactic acid/polypropylene carbonate blend using the copolymer is increased. The polylactic acid-based graft copolymer of multiple graft monomers significantly improves the compatibility between polylactic acid and polypropylene carbonate, and the mechanical properties and thermal stability of the obtained blend material can still be significantly improved while maintaining good biodegradability, melt flow pro