As low-magnification images show (Figures2(a) and
2(c)), two fracture surfaces exhibit the same morphology:
the PU particles are randomly distributed within the PLA
polymer matrix without obvious agglomeration. However,
high-magnification images (Figures2(b)and2(d))showthat
their fracture surfaces are totally different. For the fracture of
the PLA/PU film, the surface of the individual PU particle
is relatively smooth. In comparison with the fracture of
the PLA/PU/GO (0.5%) film, the surface of the individual
PU particle is wrapped by layer-stacked GO sheets. Our
fabrication process is presented to explain the combination
of GO sheets and PUparticles in PLA polymer matrix.