Civil Engineering Reference
In-Depth Information
alcohol reinforced by cellulose nanowhiskers and montmorillonite using
in-situ
polym-
erization without using any solvent or surfactants. h ey found that sulfonic acid resi-
dues at the CNW surface, which were let over from the acid hydrolysis treatment, acted
as catalysis for the polymerization reaction of furfuryl alcohol. h e use of biobased
thermosets clearly represents an area of signii cant interest, since further combination
of environmental friendly high performance materials with cellulosic nanostructures
can surely give the opportunity of creating new high performance hybrids.
6.4.2.1
CNR and Metallic Nanoparticles
h e previous paragraph underlined the possibility to use cellulose nanoreinforcements
as i llers in thermosetting matrices in order to improve those structural properties that
are useful for the i nal practical applications. However, in order to prepare polymer
materials with enhanced properties, mixtures of various nanoi llers have to be used
with polymer matrices. In the case of thermosetting matrices, few papers are avail-
able in the literature on the combined use of hybrid organic/inorganic reinforcements
in these specii c matrices. For polyurethane matrices, the synthesis and characteriza-
tion of silver nanoparticle polyurethane coated composites is reported [207], which is
prepared with the help of hydroxyethyl cellulose, showing how synthetic nanosilver
particles adsorbed onto polyurethane foam could exhibit a marked activity against cer-
tain species of water-borne bacteria. Considering the functional properties of cellulosic
nanoreinforcements and metallic nanoparticles, their future use as multifunctional
nanoi llers within polymer matrices is possible. Since the hydrophilic surface of cel-
lulosic nanostructures enables suitable blending with water-based polymer matrices
and waterborne polyurethane commonly used in various products, including coatings,
binders, adhesives, sealants, i bers, and foams, the improvement of WPU's mechani-
cal and antimicrobial properties is valuable. In Liu
et al.
[158] , nanocomposites com-
posed of carboxylated cellulose nanocrystals (CCN) and silver nanoparticles (AgNPs)
were prepared and introduced into WPU as nanoi llers. h e incorporation of the CCN/
AgNPs as bi-functional i llers in WPU improved polymer mechanical and antimicro-
bial properties. Regarding their specii c use in block copolymers, Tercjak
et al.
[208]
used cellulose nanocrystals (CNC) to prepare novel polymeric composites based on
a self-assembled poly (styrene-b-ethylene oxide) (PS-b-PEO) block copolymer with
and without Au nanoparticles synthesized using HAuCl
4
as a precursor. In this specii c
application, the block copolymer was used as a template in order to coni ne cellulose
nanocrystals in one of the blocks: this can open new i elds of applications of these novel
composites with interesting electrical properties. Galland
et al.
[209] i rstly function-
alized cellulose nanoi brils (NFC) with
in-situ
precipitated magnetic nanoparticles,
revealing how precipitation conditions can inl uence particle size distributions, which
in turn af ect the magnetic properties of the material (Figure 6.4A). Subsequently, a
method for impregnation of wet NFC network templates with a thermosetting epoxy
resin was developed, enabling the preparation of well-dispersed epoxy-NFC nanocom-
posites with high ductility and moisture durable mechanical properties. Furthermore,
cellulose i brils interact positively with the epoxy during curing (covalent bond for-
mation and accelerated curing). Potential large scale development of epoxy-NFC and
magnetic nanocomposites was further demonstrated with the manufacturing of 3D
shaped compression-moulded objects.
