Mater-Bi and its composites at 25 wt% fiber content are presented
in Fig. 6. The effect of alkali treatment of Alfa fibers with two different
concentrations of NaOH solution (1% and 5% w/v) on the
mechanical properties of biocomposites is also enumerated in
Table 3. Incorporation of 1ATA fibers in which small amounts of
hemicellulose and lignin remain and of 5ATA fibers in which hemicellulose
and lignin were removed [31], has a positive effect on the
Young’s modulus and the tensile strength of the biocomposites. It
was found that the modulus of biocomposites with 1ATA and
5ATA increased to the tune of 2.7% and 8.3%, respectively, as compared
with MaterBi /UA biocomposites at 25 wt% fibers loading.
At the same way, a significant improvement in tensile strength
was also achieved with the incorporation of alkali treated Alfa
fibers in the biocomposite as compared with the untreated fibers
composite and at the same reinforcement content. This enhancement
is proportional with the concentration of the alkali treatment.
A similar trend was observed by Jandas et al. [42] for
biocomposites based on banana fibers and polylactic acid. The
authors showed that higher strength in biocomposites was
obtained with NaOH treatment of banana fiber as compared with
the untreated banana fiber composite. In fact, the alkali treatment
of natural fibers improved the cellulose level in the plant and also
increased the roughness of the fibers surface because of the partial
or the total removal of non-cellulosic materials like lignin, hemicelluloses
and wax [31,43,44]. This results in enhancement in the
adhesion and the load transfer at the Mater-Bi matrix-fiber interface
rising the maximum tensile strength and Young’s modulus
of the biocomposite. The good matrix–fiber adhesion is quite
expected in the case of composites prepared with biopolymer