| abstract |
An expanded bead of a polylactic acid resin, having an exterior surface, a surface region including the entire exterior surface and having a weight of one-sixth to one-fourth the weight of the expanded bead, and a center region located inside the surface region and having a weight of one-fifth to one-third the weight of the expanded bead, wherein the expanded bead, the surface region and the center region, after having been subjected to a pretreatment including a heat treatment at 110° C. for 120 minutes followed by cooling at a cooling speed of 2° C./min, have endothermic calorific values of (Br:endo), (Brs:endo) and (Brc:endo), respectively, when measured by heat flux differential scanning calorimetry at a heating speed of 2° C./min in accordance with JIS K7122 (1987), and wherein (Br:endo) is greater than 25 J/g and (Brs:endo) is smaller than (Brc:endo) and is not smaller than 0 J/g. |