New Nanocomposite Materials Based on Cellulose Fibers and Other Biopolymers - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 154

Chapter 14
New Nanocomposite materials Based on
Cellulose Fibers and other Biopolymers
Carmen S. R. Freire, Susana C. M. Fernandes, Armando J. D. Silvestre,
Alessandro Gandini, and Carlos Pascoal Neto
iNtroduCtioN
The use of natural (cellulose) fibers as reinforcing components in polymeric composite
materials has been extensively explored during the last few years (Belgacem, 2008),
mainly in response to the economic and environmental concerns associated with the
extensive exploitation of petroleum-derived products. The main advantages of natural
fibers, when compared with their synthetic or inorganic counterparts, are their biode-
gradability, high availability, diversity, abundance, renewability, low cost, low energy
consumption, low density, high specific strength and modulus (with fibers possessing
an adequate aspect ratio), high sound attenuation and comparatively easy processing
ability, due to their flexibility and non-abrasive nature (Bledzki, 1999; Pommet, 2008).
Additionally, cellulose-based composites are also very attractive materials because of
their good mechanical properties sustainability and environmental-friendly connota-
tion, and have been used in a wide range of applications, such as in building, engineer-
ing, and automobile industries, as well as for the processing of furniture, packaging
materials, recreation boats and toys, among others (Bledzki, 1998).
In addition to “conventional” vegetal cellulose fibers ( Figure 1A) , other forms of
cellulose have been assessed in the last few years. The use of micro and nano-cellulose
fibers, namely whiskers, obtained from a marine species (Samir, 2005), bacterial cel-
lulose produced by some bacterial strains (Pecoraro, 2008) as well as micro- or nano-
fibrillated cellulose prepared by mechanical, enzymatic or chemical treatments of the
vegetal fibers (Nakagaito, 2004), for the development of high performance composite
materials is attracting researchers from diverse fields (Dufresne, 2008; Lee, 2009), as
the addition of very modest amounts of nano fibers leads to new composite materi-
als with superior mechanical properties and new functionalities (Klemm, 2009) when
compared with their conventional cellulose fibers counterparts.
Nanofibrillated cellulose (NFC) (Figure 1B) can be obtained from conventional
cellulose fibers by different methods as mentioned before, in the form of aqueous
suspensions bear the appearance of highly viscous, shear-thinning transparent gels.
The fibrils have high aspect ratios and specific surface areas combined with remark-
able strength and flexibility. Depending on the disintegration process, their dimensions
vary, and fully delaminated NFC consists of long (in the micrometer range) nanofi-
brills (diameter =10-20 nm) (Dufresne, 2008; Nakagaito, 2004).