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In Situ FTIR Spectroscopy Study on the Melting Process of Isotactic Poly(propylene)
Author(s) -
Zhu Xinyuan,
Yan Deyue
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20010401)202:7<1109::aid-macp1109>3.0.co;2-1
Subject(s) - tacticity , crystallization , fourier transform infrared spectroscopy , materials science , polymer chemistry , macromolecule , polymer , isothermal process , activation energy , infrared spectroscopy , melting temperature , spectroscopy , crystallography , chemical engineering , composite material , chemistry , polymerization , thermodynamics , organic chemistry , biochemistry , physics , quantum mechanics , engineering
The melting process of isotactic poly(propylene) (iPP) sample isothermally crystallized at 130°C for half an hour is carefully studied by means of variable‐temperature FTIR spectroscopy and DSC. Based on the IR intensity changes of regularity and conformational bands vs. temperature, it is found that the helical structure of macromolecular chains can be retained in the iPP melt after the polymer crystals are melted. When temperature is somewhat higher than 170.5°C, the macromolecules get sufficient energy from surroundings to overcome the energy barrier of helical structure, so the quantity of helical structure in iPP melt reduces dramatically. This conclusion is also confirmed by DSC studies on crystallization behavior of different iPP melts. The activation energy to destroy the helical structure of iPP melt is 60.1 kcal/mol determined by the Snyder method. After the major transition, some level of order still persists in the melt and it is gradually lost at higher temperatures.