Civil Engineering Reference
In-Depth Information
capacity, tensile strength and Young's modulus, which can be successfully exploited in
the development of innovative nanostructured composite materials. Dif erent synthesis
and characterization aspects of the bacterial cellulose are discussed in Chapters 2 and
4. Chapter 3 discusses the synthesis and chemistry of cellulose whiskers, nanoi bril-
lated cellulose and the synthesis of nanocomposites using polyurethane as the polymer
matrix. Chapter 4 comprehensively discusses the structure, properties and methods
of characterization along with the growth conditions for bacterial cellulose. Dif erent
modii cation strategies to alter the properties of bacterial cellulose for certain specii c
applications are also discussed in this chapter. h ese modii cation strategies include
both physical and chemical modii cations. Chapter 6 focuses on the synthesis of mul-
tifunctional ternary polymer nanocomposites using cellulosic nano-reinforcement
with an emphasis on nanocrystalline cellulose (NCC), microi brillated cellulose nano-
i bers (MFC) and bacterial cellulose (BC). Chapter 8 of the topic comprehensively dis-
cusses the nanocellulose-based liquid crystalline composite systems in detail. h e main
emphasis of this chapter is on nanocrystalline cellulose, microcrystalline cellulose,
composites, i lms and electrospun i bers. Chapter 11 describes in detail the isolation
of nanocellulose from numerous sources and its utilization for fabrication methods,
its characterization, drying processes and modii cation. h e chapter also discusses the
application of nanoscale cellulosic materials in polymer nanocomposites. Chapter 13
is focused on the cellulose whiskers procured from kenaf i bers. Dif erent thermal and
dynamic mechanical properties of the nanocomposites are also discussed in this chap-
ter. Chapter 4 focuses on the processes in cellulose derivative structures. h e main steps
that are generally involved in the preparation of cellulose nanocrystals and microi bril-
lated celluloses are shown in reference [49].
Figure 1.4
shows the transmission electron micrographs (TEM) of microcrystalline
cellulose obtained from dilute suspensions of cotton, sugar beet pulp, and tunicin (the
cellulose extracted from tunicate) whiskers [48].
Microcrystalline cellulose has been found to be insoluble in common solvents gen-
erally used in the preparation of nanocomposites. h e MCC has been found to form
colloidal suspensions when suspended in water (Figure 1.5). Dif erent parameters of
MCC such as dimensions of the dispersed particles, surface charge and their size poly-
dispersity control the stability of these suspensions [48].
Nanocrystalline cellulose (NCCs) are general referred to as rigid rod-like crystals
having a diameter in the range of 10-20 nm and lengths of a few hundred nanometers
[47]. Figure 1.6 depicts the location and extraction of nanocrystalline cellulose [50]
Figure 1.7 shows the TEM images of some of the nanocrystalline cellulose obtained
using sulfuric acid hydrolysis. Nanocellulose contains an abundance of hydroxyl groups
susceptible to various chemical reactions. h e nanocellulosic materials such as nanoi -
bers are also processed to produce the micro/nanocrystal using several pretreatments.
Some of the common treatments include the removal of the amorphous regions at the
interface of microcrystalline domains in these i bers by acid treatment [46]. For a num-
ber of applications nanocellulose is modii ed using dif erent techniques. Some of the
commonly used techniques include carboxylation, esterii cation, silylation, cationiza-
tion, and polymer grat ing [47, 53].
A summary of the dif erent chemical modii cation techniques used to alter the sur-
face characteristics of nanocellulose can be found in reference [47].
