Formation and morphology of "shish-like" fibril crystals of aliphatic polyesters from the sheared melt

Shinichi Yamazaki, Manabu Itoh, Takuya Oka, Kunio Kimura

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

We found the formation of "shish-like" fibril crystals of aliphatic polyesters such as poly(l-lactic acid) (PLLA), poly(ε-caprolactone) (PCL), poly(12-hydroxydodecanoic acid) (PHDA) and poly(16-hydroxyhexadecanoic acid) (PHHA) from the sheared melt with shear rate over(γ, ̇) = 5 s-1 observed by polarizing optical microscope (POM). The melting temperature Tms of obtained fibril crystals of PLLA and PCL were higher than those of spherulites and were close to the equilibrium melting temperature Tm0. The small angle X-ray scattering (SAXS) patterns from the bulk sample including fibril crystals, small amount of unoriented small crystals and amorphous showed no peaks arose from the existence of long periods in fibril crystals. These are the evidence that the observed fibril crystals consist of assemblies of a lot of extended chain crystals (ECCs). We observed the morphology of moderately extracted single strand of fibril crystals at the magnification of POM by means of scanning electron microscope. We found that macroscopic fibril crystals of PLLA with diameter d = 10 μm consist of the bundle structure of microscopic fibril crystals with d = 2 μm. From POM observation of the formation of fibril crystals of PLLA and PCL, we showed phase diagrams of molecular weight M and crystallization temperature Tc for the formation of fibril crystals. From these phase diagrams, we evaluated a critical M and Tc for the formation of fibril crystals. Moreover, from the sequential melting and crystallization experiments, it was implied that the entanglement and transesterification play an important role on the formation of fibril crystals of aliphatic polyesters.

Original languageEnglish
Pages (from-to)58-68
Number of pages11
JournalEuropean Polymer Journal
Volume46
Issue number1
DOIs
Publication statusPublished - Jan 2010

Fingerprint

Polyesters
polyesters
Crystals
crystals
lactic acid
Lactic acid
optical microscopes
Lactic Acid
Microscopes
melting
Crystallization
Phase diagrams
Melting point
phase diagrams
crystallization
spherulites
acids
Acids
Transesterification
magnification

Keywords

  • Aliphatic polyester
  • Crystallization
  • Fibril crystal
  • Poly(l-lactic acid)
  • Shear flow
  • Shish-kebab

ASJC Scopus subject areas

  • Polymers and Plastics
  • Physics and Astronomy(all)
  • Organic Chemistry

Cite this

Formation and morphology of "shish-like" fibril crystals of aliphatic polyesters from the sheared melt. / Yamazaki, Shinichi; Itoh, Manabu; Oka, Takuya; Kimura, Kunio.

In: European Polymer Journal, Vol. 46, No. 1, 01.2010, p. 58-68.

Research output: Contribution to journalArticle

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