Civil Engineering Reference
In-Depth Information
Grat ing of synthetic polymers onto cellulose and cellulose derivatives is a useful
method to improve the qualities of both materials and to expand the range of their
applications. Cellulose acetate grat ing (initiated by free-radical, ionic processes or by
gamma-irradiation) aims at the introduction of some branches of synthetic polymers
into the main chain, to confer specii c additional properties to the substrate itself with-
out destroying its intrinsic characteristics. h us, literature presents [138]:
•
grat ing of ethylene-co-maleic anhydride and styrene-co-maleic anhy-
dride copolymers onto cellulose acetate and methyl cellulose;
•
grat ing of N-vinyl carbazole on cellulose acetate i lms by a simultaneous
Co/60-gamma irradiation grat ing technique;
•
the extent of grat ing conversion and phase homogeneity in a cellulose
acetate/poly(styrene-co-maleic anhydride) grat ing reaction system; and
•
the grat ing reaction between cellulose acetate and acrylic monomers,
which adds new traits to cellulose acetate. Hydrophobic methyl acrylate
and methyl methacrylate can help improve the dimensional stability of
cellulose acetate.
In another recent review, homogeneous and heterogeneous grat ing of cellulose and
cellulose derivatives by several dif erent methods, including ring-opening polymer-
ization, is reported [139]. By grat ing the cellulose derivative substrates, they become
easily dispersible in the polymer matrices and may be used as reinforcing elements
to improve the mechanical and/or barrier properties of biocomposites. h us, interest-
ing features can be achieved, anticipated to be utilized for various applications such as
encapsulation and release of drugs. Moreover, it is known that grat ed cellulose deriva-
tives, such as hydroxypropyl cellulose, hydroxyethyl cellulose, ethyl cellulose, etc., can
achieve good mechanical properties if possessing a good biocompatibility, which is
especially useful in applications as materials for surgical repair. In aqueous solutions,
the grat ed i bers commonly self-assemble into micelles which may lead to their future
application as solubilizing agents for hydrophobic drugs. h us, the capacity of polymer-
grat ed cellulose derivatives to encapsulate volatile molecules for slow release in ethanol
has been investigated as a possible application in the perfume industry.
Mechanical properties are important for the practical use of blend i bers. Usually,
the poor compatibility of the component polymers may result in extremely low tenac-
ity of the blend i bers. Literature reports [140] that the tenacity of cellulose/chitosan
blend i lms increased up to a 20% chitosan content, which was explained by the occur-
rence of specii c interactions between cellulose and chitosan molecules. Improvement
of tenacity and of the initial modulus of blend i bers may therefore be attributed to the
presence of the interactions between cellulose and chitosan molecules in the i bers.
Also, the cellulose and polyacrylonitrile (PAN) molecules form miscible blend pairs in
the dimethylacetamide-LiCl solvent system, their miscibility being due to the specii c
interactions between a hydroxyl group of cellulose and a nitrile group of PAN.
Other studies provide a basic structure-property relationship analysis for ethylcel-
lulose/chitosan blends applications in the i lm and i ber industry [141] by means of
Fourier transition infrared spectra, wide-angle X-ray dif raction, dif erential scanning
calorimetry, scanning electronic microscopy, polarizing light microscopy. h us,
