Civil Engineering Reference
In-Depth Information
interface characteristics through an optimization of dimensions and geometries of the
various i llers.
6.4.1
h
ermoplastic Matrices and CNR-Based Systems
Besides application in their pure form, it is possible to use cellulose nanoreinforce-
ments extracted from dif erent natural sources and in their dif erent forms in thermo-
plastic polymer-based composites. Cellulose nanocrystals, for example, have attracted
signii cant attention during the last decade as potential i llers in dif erent polymers.
Major studies have shown that NCC can be used as i llers in a nanocomposite approach
to improve mechanical, thermal and barrier properties [8, 27, 43, 136-139]. Cellulose
whiskers were presented in 1995 [140], while their application in the fully biobased
nanocomposite production is of interest in both biomedical and food-packaging i eld.
Fortunati
et al.
[141] have recently published a paper showing a “smart” packaging
material, based on innovative nanocomposites i lms prepared by the addition of cel-
lulose nanocrystals, with silver nanoparticles, in a matrix of polylactic acid, PLA. h is
i lm could generate an antibacterial ef ect against
Staphylococcus aereus
and
Escherichia
coli
other than improvement of mechanical properties opening perspective applica-
tions of these formulations as food-active packaging. More recently, the idea to prepare
and characterize “green” thermoresponsive hydrogels of poly (N-vinylcaprolactam),
PNVCL, with improved mechanical properties by using biocompatible materials such
as nanocrystalline cellulose, as i ller, and a frontal polymerization technique, was
investigated by Sanna
et al.
[142] and the inl uence of CNC on the swelling behavior,
morphology, rheological features of the obtained hydrogels, was deeply investigated.
Considering their safety and ei cacy, NCC has attracted increasing attention in bio-
medical applications. Toxicity tests conducted so far indicate that NCC is nontoxic to
cell [143], and does not give serious environmental concerns [144, 145]. Recently NCC
has demonstrated utility for l uorescence bioassay and bio-imaging applications [146,
147]. Moreover, Rescignano
et al.
[148] reported about the production of a new gen-
eration of hybrid bio-nanocomposites based on a poly (vinyl alcohol) (PVA) matrix
reinforced with a combination of cellulose nanocrystals and poly (D, L lactide-co-
glycolide) (PLGA) nanoparticles (NPs) loaded with bovine serum albumin l uores-
ceinisothiocynateconjugate (FITC-BSA). h e authors demonstrated that the studied
bio-nanocomposite i lms are suitable to vehiculate biopolymeric nanoparticles to adult
bone marrow mesenchymal stem cells successfully, representing a new tool for drug
delivery strategies. h e reinforcing ef ect of cellulose whiskers was also compared to the
inl uence of i brillated cellulose in poly (styrene-co-butyl acrylate) latex. It was shown
that both i llers led to an increase in tensile modulus and tensile strength. However, the
incorporation of nanoi brillated cellulose resulted in signii cantly higher values, due
to the entanglements between the i brils leading to a rigid network of cellulose i brils.
In addition, dynamic-mechanical analysis showed a higher thermal stability (higher
storage modulus) in the rubbery state of the polymer latex when reinforced with i bril-
lated cellulose, compared to whiskers [149]. However, the possibility to increase the
barrier properties of PLA i lm producing PLA nano-biocomposite systems reinforced
with unmodii ed and surfactant modii ed cellulose nanocrystals by solvent casting
methods, were recently demonstrated [150], underlining the positive ef ect of cellulose
