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Pre‐melting temperature effect on the isothermal melt crystallization and multiple melting behavior of syndiotactic polystyrene
Author(s) -
Chiu Fangchyou,
Shen Kuanyeu,
Tsai Stanley H. Y.,
Chen Chienming
Publication year - 2001
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10786
Subject(s) - materials science , crystallization , differential scanning calorimetry , nucleation , avrami equation , thermodynamics , activation energy , polystyrene , isothermal process , kinetics , tacticity , melting point , crystal (programming language) , crystallography , chemical engineering , crystallization of polymers , chemistry , composite material , polymer , polymerization , physics , quantum mechanics , computer science , programming language , engineering
This work examined how pre‐melting temperature (T max ) 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 T max 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 T max specimens at various crystallization temperatures (T c 's). Our results indicated that the nucleation type of sPS is T max and T c 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 T max . From the melting behavior study, we believe that the T max and T c ‐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.