Mechanical Properties.
The densities, moisture contents, and
tensile properties of the TOCN films prepared from the softwood
and hardwood celluloses are listed in Table 1. Because the
density of cellulose I crystals is 1.63 g cm-3,17 the measured
values of 1.45-1.46 g cm-3 indicate the presence of some
disordered regions in the TOCN films. The densities and
moisture contents of the TOCN films were very similar to those
of commercial cellophane film.
However, the tensile strengths
and Young’s moduli of the TOCN films were more than 200%
and about 100%, respectively, larger than for cellophane film.
The high crystallinity (ca. 75%) and the high aspect ratios of
the nanofibers likely resulted in such high and characteristic
strengths of the TOCN films. Interestingly, the tensile strengths
of TOCN films prepared from the softwood and hardwood
celluloses were not significantly different.