Agriculture Reference
In-Depth Information
barrier thus fulfilling requirements for food and pharmaceuticals so-called green packaging.
Although it is still at the beginning, application of bio-nanocomposites with cellulose fibers in
the field of optoelectronic is also promising [64].
There are reports describing isolation of cellulose nanofibers from sugar beet shreds and
their usage in fabrication of nanocomposites. In the case of cellulose filled nanocomposites a
large mechanical reinforcement effect was observed which could be explained by the
formation of a rigid nanofibril network linked by strong hydrogen bonds [65]. Leitner et al.
[66] reported cellulose isolation from sugar beet chips and their further processing by high-
pressure homogenizer. Cellulose sheets obtained by casting and slow evaporation of water
showed higher strength and stiffness when homogenized cellulose was used compared to
unhomogenized one. These cellulose sheets showed significantly better mechanical
performance than Kraft paper tested for reference. Furthermore, the addition of cellulose
nanofibrils to a polyvinyl alcohol and a phenol-formaldehyde matrix, respectively,
demonstrated excellent reinforcement properties.
Cellulose nanofibers were successfully prepared from de-pectinated sugar beet shreds
using chemical (alkali and bleaching) treatments and high-pressure homogenization [67].
Chemical composition, morphological features, crystallinity and thermal degradation
characteristics of the resultant cellulose nanofibers were characterized. The application of
high-pressure homogenizer disrupted sugar beet shreds cell wall and helped in the release of
the cellulose nanofibers while their crystallinity index was increased due to the dissolution of
amorphous fraction. The cellulose nanofibers had improved thermal stability because of what
they can be preferably used as a biocompatible material which can be applied at high
temperatures.
Suitability of sugar beet cellulose microfibrils for obtaining composite materials with
latex of poly-(styrene-
co
-butyl acrylate) was also studied [68]. The mechanical performances
of these materials were analyzed as a function of the hydrolysis level of the cellulose fibers. It
was shown that the mechanical properties of fibrillated cellulose reinforced nanocomposites
can be adjusted by varying the strength of the acid hydrolysis step. Furthermore, the influence
of hemicellulose present in aqueous suspension of cellulose nanofibers was discussed. The
properties of the aqueous suspensions of homogenized cellulose fibrils obtained by mild
chemical treatment from sugar beet shreds and consequent high-pressure homogenization was
also investigated in correlation with their susceptibility toward specific acid and basic
reagents [69]. It was interesting that suspension characteristics were dependent on the
presence of hemicellulose and pectin on the surface of cellulose fibrils.
In another study dealing with cellulose nanofibers from sugar beet shreds, mechanical
behavior of films cast from cellulose microfibrils was investigated [70]. Depending on their
purification level, individualization state, and moisture content, differences in mechanical
characteristics were observed. It was found that non-removed pectins acted as a binder
between the cellulose microfibrils thus influencing mechanical behavior of obtaining
materials.
It is not only that pectin can influence features of nanocompostes fabricated from
cellulose fibers obtained from sugar beet shreds, as it was reviewed above, but also can be
introduced itself as a bio-nanofiber into polymer matrix. An interesting approach was made to
isolate pectin form sugar beet shreds by electrospinning and blend it with polyethylene oxide
to obtain less toxic and biodegradable nanocomposites with desired properties regarding
mechanical characteristics [71].
