Effect of well-dispersed surface-modified silica nanoparticles on crystallization behavior of poly (lactic acid) under compressed carbon dioxide

Published Date

19 August 2016, Vol.98:100–109, doi:10.1016/j.polymer.2016.06.019

Title 

Effect of well-dispersed surface-modified silica nanoparticles on crystallization behavior of poly (lactic acid) under compressed carbon dioxide

• Author 

• K. Sarikhani ^a,b
• R. Nasseri ^a
• V. Lotocki ^c
• R.B. Thompson ^b,d
• C.B. Park ^e
• P. Chen ^a,b,,

• aDepartment of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
• bWaterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
• cDepartment of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
• dDepartment of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
• eMicrocellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, M5S 3G8, Canada

Received 23 February 2016. Revised 29 May 2016. Accepted 7 June 2016. Available online 9 June 2016.

Highlights

• •
  Amine-modified silica nanoparticles significantly improved crystallinity of PLA.
• •
  Hoffman-Lauritzen theory was modified to explain facilitation of crystallization.
• •
  Avrami theory predicted sporadic three-dimensional spherulites formation.
• •
  Isothermal calorimetry under compressed CO₂ showed an increase in the crystallization rate.
• •
  The crystallization mechanism of PLAs with lower Mw and D-content stayed unchanged.

Abstract

In this work, the crystallization behavior of poly (lactic acid) (PLA)/amine-modified silica nanocomposites at different loadings of amine-modified silica (1, 2, and 8 wt %) under isothermal, non-isothermal, and isothermal under compressed CO₂ is studied. A significant improvement in crystallization rate was observed after introduction of the nanoparticles. A modified Hoffman-Lauritzen nucleation theory was utilized to explain the facilitation and acceleration of the crystallization process of nanocomposites with introducing the surface energy of the nanoparticles and interfacial energy between polymer/nanoparticle into the rate equation. After incorporation of the nanoparticles, three-dimensional spherulites formed sporadically in the PLA matrix based on the prediction of the Avrami exponents of the nanocomposites. High-pressure DSC results also showed an increase in the crystallization rate at 15 bar compared with the atmospheric pressure condition. However, an increase in pressure up to 21 bar had no significant effect on the crystallization rate. The PLA nanocomposites with lower molecular weights and D-content also showed a significant increase in the crystallization rate but with no change in the crystallization mechanism.

Graphical abstract

Keywords

• Poly (lactic acid)
• Crystallization
• Silica

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• DOCX (204K)

• ∗ 
  Corresponding author. Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.

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