Civil Engineering Reference
In-Depth Information
Figure 11.27
SEM image for CNC extracted from tunicate of poly(oxyethylene) composites: (a) uni lled
POE matrix and related composites i lled with (b) 3 wt% and
(c)
6 wt% tunicin [188].
composite is illustrated in Figure 11.27 [188]. As the SEM images show, some holes can
be seen which are attributed to entrapped air within the i lm during the water evapora-
tion step despite degassing of the suspension.
In addition, NFC can be utilized to reinforce thermoplastic polymers. For instance,
Nyström
et al.
[6] produced a nanocomposite from NFC isolated from wood and poly-
pyrrole. h ey demonstrated that it is possible to coat the individual NFC with poly-
pyrrole using
in-situ
chemical polymerization to obtain an electrically conducting
continuous high-surface-area nanocomposite. Johnson
et al.
[74] studied a new bio-
based nanocomposite using TEMPO-oxidized NFC through high-intensity ultrasoni-
cation in hydroxypropylcellulose (HPC) matrix. In bionanocomposites, the polymer
matrix also should be biodegradable. In this context, Poly(ε-caprolactone) (PCL) as
semicrystalline biopolymer with a glass transition temperature around −60°C and a
melting temperature around 60°C can be considered to manufacture bionanocompos-
ite. h erefore, NFC covalently grat ed with PCL via ring-opening polymerization of
ε-caprolactone was introduced by Lonnberg
et al.
[189] . h ey evaluated the ef ect of
PCL grat length and ring-opening polymerization on the mechanical properties of the
bionanocomposite in dif erent molecular weights of the grat s. Qu
et al.
[190] added
poly(ethylene glycol-1000) (PEG) as a compatibilizer to PLA in order to improve the
interfacial interaction between the hydrophobic PLA and the hydrophilic NFC. h eir
results illustrated that when the PEG was added to the blend of PLA and NFC, the com-
posites showed signii cant improvements in tensile strength and elongations.
11.7.2
h
ermoset Polymer-Nanocellulose Nanocomposites
h ermosetting composites can be cured with low or no heat, which can be advanta-
geous for limited thermal stability of nanocellulose. h ermosetting plastics are polymer
materials that irreversibly cure. h e curing may be done through heating, radiation or a
chemical reaction (e.g., a two-part epoxy). Once the curing is complete, the thermoset
cannot be melted into a liquid form. Several thermosets, including epoxy, formalde-
hydes and polyester, have been investigated for use with nanocellulose in nanocom-
posites. A high-strength elastomeric nanocomposite has successfully been prepared by
dispersing microcrystalline cellulose in a polyurethane matrix [176, 177]. h e SEM and
TEM micrographs show the use of CNC with water-bond polyurethane as a matrix in
Figures 11.28 [177] and 11.29 [176].
Epoxy-based nanocellulose composites have the potential for wide application due
to their high mechanical properties. Epoxy is a thermosetting copolymer, also known
