of PDLLA were improved 58% (from 3.8 to 6.0 GPa) and
210% (from 25 to 78 MPa), respectively. The high aspect ratio
of the CNFs and their strong web structures contributed greatly
to the large strength improvement. A similar filtration process
has been used by Nakagaito et al. and Larsson et al. to fabricate
cellulose nanocomposites using commercially available PLA
fiber and latex, respectively.
22,23
The composite sheets (300μm
thick) and films obtained by hot-pressing are tested for their
tensile properties. Thicker samples prepared in the present
work enabled us to conduct three-point bending test,
eliminating the need for gripping the brittle PLA for the
tensile test. The linear increase in the flexural properties
measured agrees with the tensile property improvements
observed by the above two groups at the same range of CNF
loadings. Figure 4 shows that the strain at break of PDLLA was