Crystallization kinetics of poly(L-lactide)/carbonated hydroxyapatite nanocomposite microspheres

Wen You Zhou, Bin Duan, Min Wang, Wai Lam Cheung

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Abstract

Microspheres consisting of carbonated hydroxyapatite (CHAp) nanoparticles and poly(L-lactide) (PLLA) have been fabricated for use in the construction of osetoconductive bone tissue engineering scaffolds by selective laser sintering (SLS). In SLS, PLLA polymer melts and crystallizes. It is therefore necessary to study the crystallization kinetics of PLLA/CHAp nanocomposites. The effects of 10 wt% CHAp nanoparticles on the isothermal and nonisothermal crystallization behavior of PLLA matrix were studied, using neat PLLA for comparisons. The Avrami equation was successfully applied for the analysis of isothermal crystallization kinetics. Using the Lauritzen-Hoffman theory, the transition temperature from, crystallization Regime II to Regime III was found to be around 12O0C for both neat PLLA and PLLA/CHAp nanocomposite. The combined Avrami-Ozawa equation was used to analyze the nonisothermal crystallization process, and it was found that the Ozawa exponent was equal to the Avrami exponent for neat PLLA and PLLA/CHAp nanocomposite, respectively. The effective activation energy as a function of the relative crystallinity and temperature for neat PLLA and PLLA/CHAp nanocomposite under the nonisothermal crystallization condition was obtained by using the Friedman differential isoconversion method. The Lauritzen-Hoffman parameters were also determined from the nonisothermal crystallization data by using the Vyazovkin-Sbirrazzuoli equation. CHAp nanoparticles in the composite acted as an efficient nucleating agent, enhancing the nucleation rate but at the same time reducing the spherulite growth rate. This investigation has provided significant insights into the crystallization behavior of PLLA/CHAp nanocomposites, and the results obtained are very useful for making good quality PLLA/CHAp scaffolds through SLS.

Original languageEnglish (US)
Pages (from-to)4100-4115
Number of pages16
JournalJournal of Applied Polymer Science
Volume113
Issue number6
DOIs
StatePublished - Sep 15 2009

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Keywords

  • Biomaterials
  • Carbonated hydroxyapatite
  • Crystallization
  • Nanocomposites
  • Poly(L-lactide)

ASJC Scopus subject areas

  • Chemistry(all)
  • Surfaces, Coatings and Films
  • Polymers and Plastics
  • Materials Chemistry

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