writer：Defeng Wu, Liang Wu, Bin Xu, Ming Zhang.
keywords：polylactide; clay; nanocomposites; interclation; cold crystallization; degradation.
source：期刊
specific source：Polymer International
Issue time：2009年

Polymer International, 2009, 58(3), 430-436.

 ABSTRACT:

BACKGROUND: The aim of the work presented was to study the nano-structural evolution of the clay tactoids during the isothermal cold crystallization of the polylactide/clay nanocomposites (PLACNs). An interesting degradation behavior of the matrix PLA, however, was observed simultaneously with nano-structural evolution. Thus the possible mechanism of degradation and structural evolution was discussed in this paper.

RESULTS: The evolution of nano-structure and the degradation were studied online or offline using parallel plate rheometer, X-ray diffractometer (XRD), transmission electron microscope (TEM), differential scanning calorimeter (DSC), nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and thermogrametric analysis instrument (TGA). The results showed that the intercalation level of the clay tactoids further increased during cold crystallization, leading to a simultaneous degradation of the PLA matrix, which was further confirmed by the remarkable change of small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) flow behavior of the PLACNs before and after cold crystallization.

CONCLUSION: The increase of intercalation level of the tactoids is due to the diffuse in movement of the PLA chain segments during cold crystallization. In this case, the chain end scission occurs more easily especially on those PLA chains around the loose edge and defect site of the tactoids during crystallization, which results in a simultaneous degradation of the PLA matrix. Both the linear and nonlinear dynamic viscoelastic properties hence present remarkable change after cold crystallization.

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http://www3.interscience.wiley.com/journal/122221986/abstract