Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbon fiber and poly(trimethylene terephthalate)

Abstract

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

References

[1] Ho R M, Ke K Z, Chen M. Crystal structure and banded spherulite of poly(trimethylene terephthalate). Macromolecules, 2000, 33: 7529-7535

[2] Yun J H, Kuboyama K, Chiba T, Ougizawa T. Crystallization temperature dependence of interference color and morphology in poly(trimethylene terephthalate) spherulite. Polymer, 2006, 47: 4831-4838

[3] Chuah H H. Orientation and structure development in poly(trimethylene terephthalate) tensile drawing. Macromolecules, 2001, 34: 6985-6993

[4] Run M T, Yao C G, Wang Y J, Gao J G. Isothermal crystallization kinetics and melting behaviors of nanocomposites of poly(trimethylene terephthalate) filled with nano-CaCO₃. J Appl Polym Sci, 2007, 106: 1557-1567

[5] Wang B J, Li C Y, Jennnifer H, Cheng S Z D, Geil P H, Grebowicz J, Ho R M. Poly(trimethylene terephthalate) crystal structure and morphology in different Length scales. Polymer, 2001, 42: 7171-7180

[6] Chuang W T, Hong P D, Chuah H H. Effects of crystallization behavior on morphological change in poly(trimethylene terephthalate) spherulites. Polymer, 2004, 45(7): 2413-2425

[7] Liu Z J, Chen K Q, Yan D Y. Crystallization, morphology, and dynamic mechanical properties of poly(trimethylene terephthalate)/clay nanocomposites. Euro Polym J, 2003, 39: 2359-2366

[8] Chen J, Yang D C. Phase behavior and rhythmically grown ring-banded spherulites in blends of liquid crystalline poly(aryl ether ketone) and poly(aryl ether ether ketone). Macromolecules, 2005, 38: 3371-3379

[9] Keith H D, Padden F J. Ringed spherulites in polyethylene. J Polym Sci1958, 31: 415

[10] Schultz J M, Kinloch D R. Transverse screw dislocations: A source of twist in crystalline polymer ribbons. Polymer, 1969, 10: 271-278

[11] Bassett D C, Hodge A M. On lamellar organization in banded spherulites of polyethylene. Polymer, 1978, 19: 469-472

[12] Keller A., Windle A. H. The origin of banded textures induced by shear—a suggested scheme and a relevant rheological effect. J Non-Newtonian Fluid Mechanics, 1996, 67: 241-268

[13] Keith H D, Padden F J. Twisting orientation and the role of transient states in polymer crystallization. Polymer, 1984, 25: 28-42

[14] Keith H D, Padden F J. Banding in polyethylene and other spherulite. Macromolecules, 1996, 29: 7776

[15] Keith H D. Banding in spherulites: two recurring topics. Polymer2001, 42: 09987-09993.

[16] Patel D, Bassett D C. On the formation of S-profiled lamellae in polyethylene and the genesis of banded spherulites. Polymer, 2002, 43: 3795-3802

[17] Lot B, Cheng S Z D. A critical assessment of unbalanced surface stresses as the mechanical origin of twisting and scrolling of polymer crystals. Polymer, 2005, 46: 577-610

[18] Bassett D C. A critical assessment of unbalanced surface stresses: some complementary considerations. Polymer, 2006, 47: 3263-3266

[19] Lot B, Cheng S Z D. Comments on:'a critical assessment of unbalanced surface stresses: some complementary considerations’ by DC Bassett. Polymer, 2006, 46: 3267-3270

[20] Chen E J H, Hsiao B S. The effects of transcrystalline interphase in advanced polymer composites. Polym Eng Sci, 1992, 32: 280-287

[21] Li T Q, Zhang M Q, Zhang K, Zeng H M. Long-range effects of carbon fiber on crystallization of semicrystalline thermoplastics. Polymer, 2000, 41: 161-168

[22] Chi W, Liu C R. Transcrystallization of polypropylene on carbon fibers. Polymer, 1999, 40: 289-298

[23] SarıN, Sinmazçlik T. Erosive wear behaviour of carbon fibre/polyetherimide composites under low particle speed. Mater and Design, 2007, 28: 351-355

[24] Kaynak C, Orgun O, Tincer T. Matrix and interface modification of short carbon fiber-reinforced epoxy.βPolym Test 2005, 24: 455-462

[25] Run M T, Song H Z, Yao C G, Wang Y J. Crystal Morphology and Nonisothermal Crystallization Kinetics of Short Carbon Fiber/Poly(trimethylene terephthalate) Composites. J Appl Polym Sci, 2007, 106: 868-877

[26] Suryasarathi B, Arup R B, Pravin V K. Fractionated crystallization in PA6/ABS blends: Influence of a reactive compatibilizer and multiwall carbon nanotubes. Polymer, 2007, 48: 356-362

[27] Wang Z G, Wang X H, Yu D H, Jiang B Z. The formation of ring-banded spherulites of poly(ϵ-caprolactone) in its miscible mixtures with poly(styrene-co-acrylonitrile). Polymer, 1997, 38: 5897-5901

[28] Huang Y P, Luo X L, Ma D Z. Ringed spherulite morphology and compatibility in the binary blends of poly(ϵ-caprolactone) with ethyl cellulose. Eur Polym J, 2001, 37: 2153-2157

[29] Bauer H, Owen A J. Some structural and mechanical properties of bacterially produced poly-β-hydroxybutyrate-co-β-hydroxyvalerate. Colloid Polym Sci, 1988, 266: 241-247

[30] Martinez S J, Sanchez C M, Barham P J, Keller A. Thermal expansion and spherulite cracking in 3-hydroxybutyrate/3-hydroxyvalerate copolymers. J Mater Sci Lett, 1989, 8: 490-492

[31] Ding J D, Zhu J X, Yang Y L. Banded spherulites of poly (ethylene oxide) and the concentric cracks within a single spherulite. Chem Res Chin Uni, 1996, 17(3): 489-499

[32] Run M T, Hu X M, Gao J G. Morphology and thermal properties of the poly(lactic acid)/carboxylic polypropylene blends. Acta Polymerica Sinica, 2007, 12: 1121-1126

[33] Xu J, Guo B H, Chen G Q. Terraces on Banded Spherulites of Polyhydroxyalkanoates. J Polym Sci: Part B: Polym Phys, 2003, 41: 2128-2134

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg