Percolation networks and transient rheology of polylactide composites containing graphite nanosheets with various thicknesses

The polylactide (PLA) composites with various layered graphite particles were prepared by the approach of solution mixing for the viscoelasticity study. Four kinds of particles with various layered structures, including natural graphite flakes, and graphite nanosheets with the thickness of similar to 25 nm and similar to 5 nm, as well as graphene were used as the filler, aiming at establishing the relationship between viscoelasticity of composites and filler structure and networks. The results reveal that transient rheological response of PLA composites shows evident sheet thickness dependence, and the stress overshoot behavior is closely related to the percolation network density during startup and reverse flow. But the strain-scaling characteristic of overshoots is independent of thickness of nanosheets and their networks. The linear dynamic rheology (molten state) and creep measurements (solid state) as well as thermal analyses were then performed to further explore the difference in dispersion and distribution among those layered graphite fillers. (C) 2015 Elsevier Ltd. All rights reserved.