Civil Engineering Reference
In-Depth Information
as biofuels, composites and nanocomposites, and other value-added chemicals and
products [1]. Due to its wider availability, low density, low toxicity, high aspect ratio,
higher specii c strength and modulus and surface reactivity it is a fascinating material
for biomedical and industrial applications [2]. h is century of advanced research in
biocomposites could be called the “cellulosic century” because extensive research in the
i eld of renewable plant resources for products are being done. Due to increased aware-
ness, nonrenewable resources are becoming scarce and our unavoidable dependence
on renewable resources has risen. Generally, it has been reported that natural i bers are
renewable and sustainable, while only living plants are renewable and sustainable from
which the natural i bers are isolated, but not the i bers themselves. h e greatest chal-
lenge in natural i ber-reinforced polymer biocomposites is the large variation in their
properties and characteristics [3]. Although cellulose has three reactive hydroxyl (-OH)
groups, it is relatively inert with most of the solvents and not soluble due to extensive
intra- and intermolecular hydrogen bonding through hydroxyl (-OH) groups, which
limit its wide and potential applications as cellulose i bers [4-6]. However, functional-
ization of hydroxyl (-OH) groups and a decrease in size (at nanoscale) of cellulose i bers
supposedly may be used in dif erent potential applications.
h e production of nanoscale cellulose and its application in the i eld of composites
has captured great attention due to its biodegradability, renewability, high strength and
stif ness, combined with its low weight. h e main reason for reinforcement of nanoscale
cellulose in composite materials is for potential exploitation of the high-stif ness of
nanocelluloses [7-9]. Currently, these cellulosic nanoparticles have been extensively
studied for dif erent potential applications such as polymer nanocomposites, protective
coatings, barrier/separation membranes and i ltration systems, scaf olds for tissue engi-
neering, transparent i lms, antimicrobial i lms, pharmaceuticals, drug delivery, organic
solar cells, supercapacitors, substrates for l exible electronics, lithium-ion batteries, etc.
[10, 11] .
In this chapter, we will describe the production of cellulose nanocrystals (CNCs) by
acid hydrolysis process from dif erent cellulosic resources. Also, the drying process and
extensive characterization of CNCs to better understand the inherent and processing
properties of this nanomaterial with functionalization is discussed as potential nano-
reinforcement. New developments in potential industrial and biomedical areas are also
discussed.
15.2
Cellulose and Its Sources
Cellulose is the most abundant organic polymer (polysaccharide) worldwide and it is
renewable, biodegradable and known to be biocompatible. Anselm Payen (1838) was
the i rst to recognize the existence of cellulose as a common material of plant cell walls
[12]. In general, cellulose can be dei ned as a tough, i brous and water-insoluble material
which acts as an essential structural support for plant cell walls. Cellulose can be obtained
from higher plants, annual crops, marine animals, and to a lesser degree in fungi, algae,
bacteria, invertebrates, and even amoeba. h e structure of cellulose varies considerably
depending on the origin sources. However, regardless of the source, cellulose is com-
monly characterized as a polydispersed linear polymer having regio-enantioselective
