Effect of Heating Rate on Lamellar Thickening of Polyethylene Terephthalate

Abstract

The effect of heating rate before isothermal annealing on the lamellar thickening of polyethylene terephthalate (PET) was investigated using differential scanning calorimeter (DSC) and transmission electron microscopy (TEM). Transmission electron microscopy showed that thickened lamellae were formed when PET was annealed near its melting temperature. After annealing, two melting peaks arose in which the higher melting point (T _m2) and corresponding fusion enthalpy (ΔH _m2) corresponded to the thickened lamellae. A low heating rate before annealing, especially in the high-temperature region above 241°C, favored the lamellar thickening of PET. We suggest the way it facilitated the lamellar thickening process was due to its reduction of the activation barrier for the α_c-relaxation.

Keywords:

• annealing
• heating rate
• lamellar thickening
• polyethylene terephthalate

Acknowledgments

The authors are grateful to the Shanghai Shuguang Project (08SG28) Program for New Century Excellent Talents in University (NCET–09–0348), National Science Foundation of China (50703011), Shanghai Rising-Star Program (08QA1402200), Program for Changjiang Scholars, and Innovative Research Team in University and the 111 Project (B08021).