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Blends of poly(lactic acid) (PLA) and poly(ethylene terephthalate glycol) (PETG) of various compositions were prepared by melt compounding and their compatibilities, physical properties, and isothermal crystallization behaviors were investigated. The calculated solubility parameters of PETG are similar to those of PLA. The interaction parameter between PLA and PETG was derived from the Flory-Huggins theory and predicted that PLA and PETG are miscible when PETG contents are below 22 wt%. In accordance with this result, the tan δ peak and glass transition temperatures of blends determined from dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) showed a single peak at PETG contents lower than 22 wt%. Tensile test results showed that the elongation at the break of blends increased with an increase in PETG content. DSC and isothermal crystallization results showed that PETG accelerates the crystallization rate of PLA at PETG contents lower than 22 wt%, indicating that PETG acts as a nucleation agent in the crystallization of PLA. Wide angle X-ray diffraction results (WAXD)showed that the crystalline structure of PLA is not affected by the incorporation of PETG.