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Frontiers of Chemical Science and Engineering

Front Chem Eng Chin    2009, Vol. 3 Issue (3) : 255-264     DOI: 10.1007/s11705-009-0008-9
Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbon fiber and poly(trimethylene terephthalate)
Mingtao RUN1(), Hongzan SONG1, Yanping HAO2
1. College of Chemistry & Environmental Science, Hebei University, Baoding 071002, China; 2. College of Economics, Hebei University, Baoding 071002, China
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The spherulites of the short carbon fiber(SCF)/poly (trimethylene terephthalate) (PTT) composites formed in limited space at designed temperatures, and their melting behaviors were studied by the polarized optical microscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), respectively. The results suggest that SCF content, isothermal crystallization temperatures, and the film thicknesses influence the crystal morphology of the composites. The dimension of the spherulites is decreased with increasing SCF content, but whether banded or nonbanded spherulites will form in the composites is not dependent on SCF content. However, the crystal morphology of the composites depends strongly on the temperature. When the isothermal crystallization temperatures increase from 180°C to 230°C, the crystal morphology of SCF/PTT composites continuously changes in the following order: nonbanded → banded → nonbanded spherulites. Discontinuous circle lines form in the film when the film thickness increases from 30 to 60 μm. Basing on the SEM observation, it is found that these circle lines are cracks formed due to the constriction difference of the different parts of the spherulites. These cracks are formed when the film is cooled from the isothermal crystallization temperature to the room temperature at a slow cooling rate; while they will disappear gradually at different temperatures in the heating process. The crack will appear/disappear first around the center of the spherulite when the film was cooled/heated. The nontwisted or slightly twisted lamellas will reorganize to form highly twisted lamellas inducing apparent banded texture of the spherulites.

Keywords poly(trimethylene terephthalate)      short carbon fiber      banded spherulites      crack     
Corresponding Authors: RUN Mingtao,   
Issue Date: 05 September 2009
 Cite this article:   
Mingtao RUN,Hongzan SONG,Yanping HAO. Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbon fiber and poly(trimethylene terephthalate)[J]. Front Chem Eng Chin, 2009, 3(3): 255-264.
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Mingtao RUN
Hongzan SONG
Yanping HAO
Fig.1  POM micrographs of the different SCF/PTT composites crystallized from melt at 205°C for 7 h with film thickness of about 30 μm
Fig.2  POM micrographs of the composites (SCF 2%) crystallized from melt at a variety of temperatures for 7 h with film thickness of about 30 μm
Fig.3  POM and OM micrographs of different composites after isothermally crystallized from melt at 205°C for 7 h; the film thickness is about 60 μm
Fig.4  SEM and AFM micrographs of circle lines on the composite’s film surface with different magnifications. (a) SEM, 250x; (b) SEM, 10000x; (c) AFM, 10000x; (d) SEM, 5000x; (e) SEM, 2500x; (f) SEM, 10000x
Fig.5  POM micrographs of the changing process of the circle lines in spherulites film with thickness of about 60 μm at a heating rate of 5°C/min
Fig.6  POM micrographs of the changing spherulites with thickness of about 60 μm at a heating rate of 5°C/min
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