Detection of Tg by modulated differential scanning calorimetry

The glassy transition of the polyethylene terephthalate (PET) samples which have been subjected to solvent induced crystallization (SINC) was investigated by modulated differential scanning calorimetry (MDSC) and density measurement. The differential of heat capacity signal, d C-p/dT from MDSC, was used to monitor the SINC process. It reveals that the T-g temperature shifts to higher value with the advancement of SINC. When the toluene-immersing time was longer (168 h), the detection of T-g become more 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.