Civil Engineering Reference
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this study, a novel method to compound BC and PLA based on thermally induced
phase separation yielding a dry pre-extrusion nanocomposite was also developed. In
another study, the ef ect of crosslinking the layered BC structure with glyoxal and the
grat ing with maleic anhydride on the physical properties of PLA-based nanocompos-
ites was reported [164]. An entirely biobased carbohydrate derived polylactide copo-
lymer was also ef ectively used to produce BC/PLA nanocomposites with improved
mechanical properties [165]. Addition of only 5 wt% of this copolymer to a composite
with 5 wt% of BC resulted in relative improvements of the Young modulus (4%) and
tensile strength (17%), when compared to the uni lled PLA or BC/PLA nanocompos-
ites. h e surface modii cation of BC with poly(lactide-grat -
-methacryloxypropyltri-
methoxysilane) was also studied as a way to increase the compatibility between BC and
PLA and thereby the properties of the composites [166].
In a dif erent fashion, the same research team reported a very fascinating green
approach for the surface modii cation of cellulose i bers based on the
in situ
attach-
ment of BC nanoi brils onto plant (hemp and sisal) i bers [167-169]. h ese nano-mod-
ii ed natural i bers were then incorporated into PLA (as well as into cellulose acetate
butyrate), and an improved interaction between the modii ed i bers and the polymer
matrices and overall mechanical performance was observed. h ese improvements were
attributed to the roughness of the i ber surface and the presence of hydroxyl groups
attached to the i bers surface, as well as to the intrinsic reinforcement ability of nanocel-
lulose. At erwards, this idea was deeply rei ned resulting in innovative hairy BC coated
sisal i bers produced by a simple slurry dipping process, in which BC nanoi bers were
oriented perpendicular to the surface of the i bers (Figure 2.19) [170]. h ese “hairy”
i bers were also used to prepare hierarchical sisal i bers-reinforced BC/PLA nanocom-
posites with improved tensile, l exural and visco-elastic properties. Similar hierarchical
nanocomposites were prepared by infusing robust nonwoven sisal preforms manufac-
tured using a papermaking process and BC as binder for the sisal i bers, with acrylated
epoxidized soybean oil [38]. By developing such kind of hierarchical nanostructured
biobased nanocomposites it is predictable to match and advance upon non-renewable
conventional polymer materials in several important biomedical and technological
i elds [172]. However, the potential high water sensitivity of these composites, arising
from the decidedly hydrophilic nature of both BC and plant i bers, could be a weakness
in several applications.
Polyhydroxyalkanoates (PHAs) are a family of intracellular biopolyesters synthesized
by bacteria as intracellular carbon and energy storage granules. Poly(3-hydroxybutyrate)
h
BC coated
ibre
matrix
ibre
BC
Figure 2.19
Schematic representation of the dif erent hierarchical nanocomposites (from let to right,
conventional plant i bers-reinforced nanocomposites, BC coated i ber-reinforced nanocomposites and
BC coated i bers-reinforced hierarchical nanocomposites). Reproduced with permission from [170].
