ISOTHERMAL CRYSTALLIZATION AND SUBSEQUENT MELTING BEHAVIOR OF POLY(ETHYLENE TEREPHTHALATE)/SILICA NANOCOMPOSITES

Abstract

The crystallization process of nanocomposites was investigated by differential scanning calorimetry (DSC) and analyzed by the Avrami method. It was found that the crystallization of pure poly(ethylene terephthalate) (PET) is fitted for thermal nucleation and three-dimensional spherical growth in the whole process, while the crystallization of PET/silica nanocomposites exhibits two stages: the first stage corresponds to athermal nucleation and three-dimensional spherical growth, and the second one corresponds to recrystallization caused by the earlier spherulite impingement. The crystallization rate increases markedly and the activation energies decrease greatly with adding silica nanoparticles. The subsequent melting behavior of the crystallized samples shows that the melting point (T_m) of nanocomposites is higher than that of pure PET, which might result from two reasons: (1) some hindrance to the PET chains caused by the nanoparticles at the beginning of the melting process; and (2) more perfect crystals being formed due to the higher crystallization temperature and lower activation energy of PET/silica nanocomposites.

Keywords:

• Crystallization
• Crystallization rate
• Differential scanning calorimetry
• Melting behavior
• Nanocomposites
• Poly(ethylene terephthalate)

Acknowledgments

Financial support from the “863” Project of the Ministry of Science and Technology (No. 2003AA333110), the Nature Science Foundation of China (No. 19974052, 51072048, and 10274085), the Nature Science Foundation of Anhui Province, China (No. 01044906), and the Foundation of Anhui Province is gratefully acknowledged.