The invention relates to a
polylactic acid foamed sheet and a preparation method thereof. The foaming ratio of the
polylactic acid foamed sheet is 20 to 30 times; the pore density is 10.2-13.4*10<9> pores for each cubic
centimeter; the
diameter of pores is 4 to 15 [mu]m, and the
thermal deformation temperature is 95 to 105 DEG C. According to the preparation method,
polylactic acid is taken as thematrix, a nucleating agent and a chain
extender are added to obtain a mixture; the mixture is extruded in a double screw extruder to obtain polylactic acid foamed modified resin; then the modified resin and optionally picked color master batch are added into the hopper of a foaming extruder composed of two
extrusion systems, which are serially connected; the mixture is melted and plasticized in the primary extruding
system, then a
foaming agent is added, then the mixture is mixed and cooled in the secondary extruding
system to obtain low temperature homogenous melt; the melt is extruded fromthe head of a controllable foaming
machine, and finally the foamed sheet is obtained after
sizing cooling, part spreading, and rolling. The provided polylactic acid foamed sheet has the advantages ofhigh foaming ratio, good foaming performance, good heatproof property, good pore structure, simple technology, and controllable cost.