Correlation of crack patterns and ring bands in spherulites of low molecular weight poly(l-lactic acid)

Siti Nurkhamidah, Eamor M. Woo

研究成果: Article同行評審

33 引文 斯高帕斯(Scopus)

摘要

Only a single type of circular circumferential crack is conventionally reported for poly(l-lactic acid) (PLLA). In this study, PLLA samples were found to exhibit as many as four crack types of different directions and patterns, which cannot be feasibly explained simply by the directional difference in coefficients of thermal expansion. Depending on crystallization temperature (T c), PLLA crystallizes into ringless or ring-banded spherulites, whereas the crack patterns are dramatically different in these two types of spherulites. In ring-banded spherulites of PLLA crystallized at intermediate T c, two uniquely different crack types are present: (1) twin circumferential cracks coinciding with the dark-bright and bright-dark boundary and (2) radial short-segmental voids coinciding on the bright bands in spherulites. The radial short-segmental cracks on the bright band of ring-banded spherulites may be caused by PLLA crystals of radial direction with various twisting that contract laterally upon cooling. Only circumferential cracks are present in PLLA crystallized into ringless spherulites, where concentric continuous circumferential cracks are present in the ringless spherulites at low T c with finer lamellae, but discontinuous and irregular circumferential cracks are present in the ringless spherulites at high T c with coarse lamellae. Although all cracks are triggered by cooling from T c, all evidences indicate that the crack patterns and types are highly associated with the lamellar orientation, patterns, and coarseness in spherulites. [Figure not available: see fulltext.]

原文English
頁(從 - 到)275-288
頁數14
期刊Colloid and Polymer Science
290
發行號3
DOIs
出版狀態Published - 2012 2月

All Science Journal Classification (ASJC) codes

  • 物理與理論化學
  • 聚合物和塑料
  • 膠體和表面化學
  • 材料化學

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