Abstract
This work examined how pre-melting temperature (Tmax) affects the isothermal melt crystallization kinetics, the resulting melting behavior and crystal structure of syndiotactic polystyrene (sPS) by using differential scanning calorimetry (DSC), polarized light microscopy (PLM) and the wide angle X-ray diffraction (WAXD) technique. Experimental results indicated that raising Tmax decreased the nucleation rate and the crystal growth rate of sPS. The Avrami equation was also used to analyze the overall crystallization kinetics. The Avrami exponent n and rate constant K were determined for different Tmax specimens at various crystallization temperatures (Tcs). Our results indicated that the nucleation type of sPS is Tmax and Tc dependent as well. Evaluation of the activation energy for the isothermal crystallization processes revealed that it increases from 375 kJmol-1 to 485 kJmol-1 with an increase of Tmax. From the melting behavior study, we believe that the Tmax and Tc-dependent multiple melting peaks are associated with different polymorphs as well as recrystallized crystals formed during heating scans. Moreover, the percentage content of α form in the crystals formed under different crystallization conditions was estimated through WAXD experiments.
Original language | English |
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Pages (from-to) | 881-889 |
Number of pages | 9 |
Journal | Polymer Engineering and Science |
Volume | 41 |
Issue number | 5 |
DOIs | |
State | Published - 05 2001 |