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Effect of isotacticity distribution on crystallization kinetics of polypropylene
Author(s) -
Lu Hongbin,
Qiao Jinliang,
Yang Yuliang
Publication year - 2002
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.856
Subject(s) - tacticity , crystallization , materials science , differential scanning calorimetry , kinetics , polypropylene , isothermal process , microstructure , supercooling , polymer chemistry , activation energy , chemical engineering , molar mass distribution , thermodynamics , polymer , composite material , chemistry , polymerization , physics , quantum mechanics , engineering
The crystallization kinetics of isotactic polypropylene (iPP) depends not only on the undercooling but also on its microstructure characteristics. In this paper the effect of isotacticity distribution on the isothermal kinetics of iPPs in the crystallization regime III was examined by differential scanning calorimetry. The microstructure features of two commercial film grade iPPs were characterized with temperature rising elution fractionation and size exclusion chromatography. The results indicated that, although the overall isotacticities and molecular weights of two iPPs were similar, their isothermal crystallization kinetics displayed marked differences due to the disparity in isotacticity distributions. With increasing molecular weight of components containing crystallizable units, the isothermal crystallization rate exhibited a higher temperature dependence. When the isotactic defects in polypropylene chains increase with the molecular weight of components, both the fold surface free energy σ e and the work of chain folding q decreases, in spite of the higher molecular weight. © 2002 Society of Chemical Industry