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Further study on double‐melting endotherms of isotactic polypropylene
Author(s) -
Zhu Xinyuan,
Yan Deyue,
Tan Susheng,
Wang Tao,
Yan Donghang,
Zhou Enle
Publication year - 2000
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(20000705)77:1<163::aid-app22>3.0.co;2-l
Subject(s) - endotherm , tacticity , lamellar structure , crystallization , materials science , differential scanning calorimetry , recrystallization (geology) , isothermal process , crystallography , melting point , diffraction , thermodynamics , composite material , chemistry , polymerization , polymer , optics , paleontology , physics , biology
The origins of the single‐ and double‐melting endotherms of isotactic polypropylene crystallized at different temperatures were studied carefully by differential scanning calorimetry, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering. The experimental data show that spontaneous crystallization occurs when the crystallization temperature is lower than 117°C; thus the lamellae formed are imperfect. At a lower heating rate, the recrystallization or reorganization of these imperfect lamellae leads to double endotherms. On the other hand, when the crystallization temperature is higher than 136°C, two major kinds of lamellae with different thickness are developed during the isothermal process, which also results in the double‐melting endotherms. In the intermediate temperature range the lamellae formed are perfect, and there is only a single peak in the distribution of lamellar thickness. This explains the origin of the single‐melting endotherm. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 163–170, 2000