Starch Nanocomposite and Nanoparticles: Biomedical Applications - Modern Trends in Chemistry and Chemical Engineering - page 64

used in disposable items. Therefore, the interest in polymers from renewable resources
has recently gained exponential momentum and the use of biodegradable and renew-
able materials to replace conventional petroleum plastics for disposable applications
is becoming popular. Within the broad family of renewable polymers, starch is one
of the most attractive and promising sources for biodegradable plastics because of
the abundant supply, low cost, renewability, biodegradability, and ease of chemical
modifications. In recent years, plasticized starch (PS) has attracted considerable atten-
tion and has offered an interesting alternative for synthetic polymers where long-term
durability is not needed and rapid degradation is an advantage. However, compared
with conventional synthetic thermoplastics, biodegradable products based on starch,
unfortunately, still exhibit many disadvantages, such as water sensitivity, brittleness,
and poor mechanical properties. Various physical or chemical means have been used
to solve these problems, including blending with other synthetic polymers, the chemi-
cal modification, graft copolymerization, and incorporating fillers such as lignin, clay,
and multi walled carbon nanotubes.
More recently, there is an increased use of cellulose nanocrystals (CNs) as the
loading-bearing constituent in developing new and inexpensive biodegradable ma-
terials due to a high aspect ratio, a high bending strength of about 10 GPa, and a
high Young's modulus of approximately 150 GPa. The CNs from various sources
such as cotton, tunicate, algae, bacteria, ramie, and wood for preparation of high per-
formance composite materials have been investigated extensively. Both natural and
synthetic polymers were explored as the matrixes. Natural polymers such as poly(β-
hydroxyoctanoate) (PHO), soy protein, silk fi broin reinforced with cellulose whis-
kers were reported. Meanwhile, Poly-(styrene- co -butyl acrylate) (poly(S- co -BuA)),
poly(vinyl chloride) (PVC), polypropylene, waterborne polyurethane, were also used
as synthetic matrixes. The fl ax plant ( Linum usitatissimum ) is a member of the Lina-
ceae family, which is an important crop in many regions of the world. Fibers from fl ax
have been used for thousands of years to make different textile products because of
their excellent fi ber characteristics. Therefore, the search on short fi bers from fl ax as a
replacement for synthetic fi bers in many non-textile products, for example, in polymer
compounds, building materials, and absorbent materials, has attracted much attention
in the last decade.
However, incorporating fl ax cellulose nanocrystals (FCNs) in the starch-based
composite fi lms has not been reported in the literatures. In present work, it attempts
to prepare CNs from fl ax fi ber by acid hydrolysis with concentrated sulfuric acid, and
then use the resulting CNs to reinforce PS for preparation of nanocomposite fi lms with
improved performances.
The resulting fi lms were prepared by casting the mixture of aqueous suspensions
of CNs and PS in various weight ratios. The morphology, structure, and performance
of the resulting nanocomposite fi lms were investigated by scanning electron micros-
copy (SEM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry
(DSC), and measurement of the mechanical properties and water uptake.