The glassy transition of the polyethylene terephthalate (PET) sampleswhich have been subjected to solvent induced crystallization (SINC) was investigated bymodulated differential scanning calorimetry (MDSC) and density measurement. The dif-ferential of heat capacity signal

d Cp/dT from MDSC

was used to monitor the SINCprocess. It reveals that the Tg temperature shifts to higher value with the advancement ofSINC. When the toluene-immersing time was longer (168h)

the detection of T_g becomemore difficult

because some smaller peaks emerged at the lower temperatures and these are explained as the movement of small segments in the amorphous region.These observed results are due to the morphology and structure introduced by the SINC process.