Abstract: In order to research the drying process of polylactic acid (PLA) chip, the differential scanning calorimetry (DSC) was applied to measure the glass transition temperature (Tg), the melting point (Tm) and the amorphous structure of polylactic acid chip. The effects of drying time and drying temperature on properties of chip were researched. Addition, the stage drying was analyzed. Results show that longer drying time and higher drying temperature, lead to lower moisture content, but more hardened chips and lower viscosity average molecular weight. And results also show that in initial stage, relatively low temperature was applied to remove mostly water of PLA chip, then higher temperature was used to remove small amount of associated water in chip. Finally, the result indicates the optimum three-stage drying process as follows: 80℃, 4h; 100℃, 4h; 110℃, 20h, which led to low moisture content, and avoid much hardened chips and decrease of viscosity average molecular weight.

Key words: polylactic acid , drying process , moisture content , viscosity average molecular weight