TY - JOUR
T1 - Ring-banded spherulites in poly(pentamethylene terephthalate)
T2 - A model of waving and spiraling lamellae
AU - Wu, Pi Ling
AU - Woo, Eamor
AU - Liu, Hung Ling
PY - 2004/12/1
Y1 - 2004/12/1
N2 - A new aryl polyester, poly(pentamethylene terephthalate) (PPT) with five methylene groups in the repeat unit, was synthesized. Its multiple-melting behavior and crystal structure were analyzed with differential scanning calorimetry and wideangle X-ray diffraction. In addition, the spherulitic/lamellar morphology of melt-crystallized PPT was investigated. Typical Maltese-cross spherulites (with no rings) were seen in melt-crystallized PPT at low temperatures (70-90°C), but ring patterns were seen in PPT crystallized only at temperatures ranging from 100 to 115°C, whereas rings disappeared with crystallization above 120°C. The mechanisms of the rings in PPT were explained with several coordinated directional changes (wavy changes, twisting changes, and combinations) in the lamellae during growth. Scanning electron microscopy, in combination with atomic force microscopy, further proved that the ringed spherulites originated from the aggregation of sufficient numbers of edge-on lamellar crystals; the radial-growth edge-on/flat-on lamellae could be twisted and/or waved to form realistic band patterns. A postulated model properly described a possible origin of the ring bands through combined mechanisms of waving (zigzagging) and twisting (spiraling) of the lamellae during crystallization. Superimposed twisting and/or wavy models during crystallization were examined as examples.
AB - A new aryl polyester, poly(pentamethylene terephthalate) (PPT) with five methylene groups in the repeat unit, was synthesized. Its multiple-melting behavior and crystal structure were analyzed with differential scanning calorimetry and wideangle X-ray diffraction. In addition, the spherulitic/lamellar morphology of melt-crystallized PPT was investigated. Typical Maltese-cross spherulites (with no rings) were seen in melt-crystallized PPT at low temperatures (70-90°C), but ring patterns were seen in PPT crystallized only at temperatures ranging from 100 to 115°C, whereas rings disappeared with crystallization above 120°C. The mechanisms of the rings in PPT were explained with several coordinated directional changes (wavy changes, twisting changes, and combinations) in the lamellae during growth. Scanning electron microscopy, in combination with atomic force microscopy, further proved that the ringed spherulites originated from the aggregation of sufficient numbers of edge-on lamellar crystals; the radial-growth edge-on/flat-on lamellae could be twisted and/or waved to form realistic band patterns. A postulated model properly described a possible origin of the ring bands through combined mechanisms of waving (zigzagging) and twisting (spiraling) of the lamellae during crystallization. Superimposed twisting and/or wavy models during crystallization were examined as examples.
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U2 - 10.1002/polb.20246
DO - 10.1002/polb.20246
M3 - Article
AN - SCOPUS:10044240327
VL - 42
SP - 4421
EP - 4432
JO - Journal of Polymer Science, Part B: Polymer Physics
JF - Journal of Polymer Science, Part B: Polymer Physics
SN - 0887-6266
IS - 23
ER -