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Abstract
Graphene (GN)-filled polylactic acid (PLA) nanocomposites were prepared through a solution blending method with GN weight percent ranging from 0.5 to 2 wt%. Rheological, melting and crystallization behaviors of the prepared PLA/GN nanocomposites were investigated by means of dynamic rheological measurements and differential scanning calorimetry (DSC). The shear viscosities of the PLA/GN nanocomposites decreased with increasing GN content, which was remarkably different from previous reports on the modifications using traditional nanofillers (e.g., clay, carbon nanotubes, etc.). The nonisothermal melt crystallization kinetic analysis suggested that GN served as a nucleating agent and could considerably promote the PLA’s crystallization through heterogeneous nucleation. Our findings suggested that at relatively low cooling rates (ϕ ≤ 10 °C/min) even a small amount of GN promoted the nucleation and considerably increased the crystallization rate. However, the crystallinity began to decrease at higher cooling rates (e.g., ϕ ≥ 20 °C/min), especially when the GN content was high (e.g., 2 wt%), possibly owing to the GN aggregation effect considering PLA is a slowly crystallizing polymer.
Acknowledgements
The authors gratefully thank the financial support of the National Natural Science Foundation of China (Nos. 51203002, 51273001) and the “211 Project” of Anhui University. The authors are also indebted to the kind supply of materials from the Collaborative Innovation Center for Petrochemical New Materials. Dr. L. Wang (Kyoto University) and Prof. P. Geil are both appreciated for their helpful advice for improvement of our work.