Civil Engineering Reference
In-Depth Information
More recently, Siqueira
et al.
[63] applied N-octadecyl isocyanate as a grat ing agent
for modifying the surface of two types of cellulose nanoi llers. In this study the rein-
forcing capacity of nanowhiskers and MFC in PCL matrix was compared. Substantial
dif erences were observed depending on the nature of the nanocellulosic i ller. h ese
dif erences were mainly attributed to the fact that, unlike the rod-like whiskers, MFC is
capable of forming an entangled network. In particular, grat ed MFC-reinforced PCL
composites possessed higher modulus and lower elongation at break at a given loading
level compared to cellulose whisker-reinforced nanocomposites.
9.2.2
Treatment of CNW: Improvement of Cellulose Nanoi bers/
Biodegradable Matrix Compatibility
h e hydrophilic surface of the cellulose-based nanoreinforcements leads to poor inter-
action between matrix and the i ller [29]. Furthermore, the chemical compatibility is
very important in controlling the dispersion and the adhesion among them. h erefore,
it is common to see weak i ller-matrix interactions when hydrophilic whiskers were
added to hydrophobic matrices [4]. h e miscibility of cellulose nanoi llers with hydro-
phobic matrices can be improved by various surface modii cations, for example, esteri-
i cation and acylation. h e increment in the i ller/matrix compatibility produces the
enhancement of mechanical and thermal properties but also enhances the barrier
properties [30] .
Espino-Pérez
et al.
[64] have proposed a novel,
in-situ
grat ing method for cellulose
nanowhiskers (CNW) with the aim of producing a modii ed surface with enhanced
compatibility with polylatic acid (PLA) by using n-octadecyl isocyanate (CNW-ICN).
h ey have demonstrated that the grat ing induced compatibility, which provided CNW-
ICN with a nucleating ef ect on PLA, but also some thermal degradation under severe
conditions. h e increased CNW-ICN/PLA compatibility produced higher mechani-
cal properties at low CNW-ICN concentrations and higher thermal resistance of PLA,
whereas the oxygen permeability was not af ected and the water vapor permeability was
lower than the one of the comparable CNW/PLA bionanocomposites. h ey have con-
cluded that the surface grat ing of CNW with a long-chain aliphatic molecule was suc-
cessful in providing compatibilized structures, providing an easy method for designing
functional, fully-organic and biodegradable bionanocomposites based on polylactic
acid.
9.2.3
Processing of Cellulose-Based Bionanocomposites
h e polarity of cellulose whiskers makes it dii cult to disperse them in nonpolar envi-
ronments [31] . h is behavior makes the processing of cellulose-based bionanocompos-
ites very dii cult because several biodegradable polymers are mainly hydrophobic. On
the other hand, a higher degree of i ller dispersion in the polymer matrix is expected
in polar medium.
Usually, two main techniques are used to prepare cellulose-based bionanocompos-
ites [65], known as solvent casting and melt processing.
