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Crystallization‐induced shrinkage, crystalline, and thermomechanical properties of in situ polymerized cyclic butylene terephthalate
Author(s) -
Harsch M.,
KargerKocsis J.,
Apostolov A. A.
Publication year - 2008
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/app.27798
Subject(s) - crystallinity , crystallization , materials science , shrinkage , differential scanning calorimetry , composite material , polymerization , isothermal process , polymer chemistry , polymer , chemical engineering , thermodynamics , physics , engineering
The polymerization and crystallization of cyclic butylene terephthalate oligomers (CBT) were followed by fiber Bragg grating (FBG) and normal force measurements under isothermal conditions at T = 170 and 190°C, respectively. It was found that the FBG and normal force sense only the crystallization‐induced shrinkage. The course of the FBG signal and the normal force as a function of time suggested that crystallization of the polymerized CBT (pCBT) occurs in two steps. The primary crystallization‐induced shrinkage is several hundreds by contrast to the secondary one showing several tens in ppm/min unit according to the FBG results. The two‐step crystallization was confirmed by normal force measurements. The crystallinity and crystalline structure of the pCBTs were studied by differential scanning calorimetry and wide‐angle X‐ray scattering. It was found that the crystallinity and the crystalline parameters slightly differ for the pCBTs formed at T = 170 and 190°C, respectively. The pCBT produced at T = 190°C had slightly higher crystallinity and more perfect crystals than the pCBT formed at T = 170°C. The reliability of the FBG sensing was checked by thermomechanical analysis (TMA). A fair agreement was established between the thermal contraction and thermal expansion measured by FBG and TMA, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008