The elastic properties of composites depend on energy storage mechanisms at the interphase, and the relaxation time of the dispersed phase is often longer than the relaxation time of the polymer chains of the individual components. The elastic moduli (G) of the neat PLA, PLA + PHB, and CNF composites at 180 ◦C as a function of frequency are shown in Fig. 4. PLA + PHB composites showed lower elastic modulus compared to neat PLA due to poor mechanical properties of PHB. It is apparent that the storage moduli of the CNF composites were larger relative to the PLA + PHB matrix especially for the highest CNF content because of the intrinsic rigidity of CNF. This behavior can be explained by
the fact that reinforced particles restrict deformation. The slopes of the elastic moduli curves decreased
with increasing amounts of CNF, and the decrease in the slopes
of elastic moduli for the composites compared to PLA + PHB can be
explained by the microstructural changes of the polymer matrix
because of the incorporation of CNF