Abstract: A preparation method and an application method of injectable polylactic acid (PLA) microspheres are provided, which relate to the field of biomedical technologies. The preparation method of the injectable PLA microspheres include: S01, preparing a spray solution; S02, performing homogeneous emulsification on the spray solution to obtain an emulsified spray solution; and S03, drying the emulsified spray solution. The spray solution includes an oil phase and an aqueous phase, and a weight ratio of the oil phase and the aqueous phase is 1-10:1-10. The oil phase includes PLA and an organic solvent, and the aqueous phase includes a surfactant, macromolecular substances and deionized water. A particle size of the injectable PLA microspheres is basically below 60 ?m, and the injectable PLA microspheres have a complete form, are independent of each other, do not exhibit agglomeration and have good biocompatibility, which can satisfy the requirement of the injection.

Abstract: A method for preparing lactide from recovered polylactic acid, the method including the following steps: A. pretreating the recovered polylactic acid; B. extruding the treated polylactic acid from a twin screw extruder to yield a polylactic acid melt, and introducing the polylactic acid melt to a pre-depolymerization kettle; C. carrying out a chain scission reaction to break molecular chains in the polylactic acid melt and to decrease the number-average molecular weight of the polylactic acid melt to below 5000; D. conducting depolymerization reaction to yield a crude lactide; and E. purifying the crude lactide and crystallizing the purified lactide.

Abstract: A method for preparing lactide from recovered polylactic acid, the method including the following steps: A. pretreating the recovered polylactic acid; B. extruding the treated polylacitc acid from a twin screw extruder to yield a polylacitc acid melt, and introducing the polylacitc acid melt to a pre-depolymerization kettle; C. carrying out a chain scission reaction to break molecular chains in the polylactic acid melt and to decrease the number-average molecular weight of the polylactic acid melt to below 5000; D. conducting depolymerization reaction to yield a crude lactide; and E. purifying the crude lactide and crystallizing the purified lactide.