A facile approach for extracting cellulose nanocrystals (CNCs) was presented through hydrochloric acid hydrolysis of cellulose raw materials under hydrothermal conditions. The influences of preparation parameters, such as reaction time, reaction temperature, and acid-to-cellulose raw material ratio, and different neutralization methods on the yield, microstructure and properties were studied. A high yield of up to 93.7%, crystallinity of 88.6%, and a maximum degradation temperature (T max ) of 363.9 C can be achieved by combining hydrochloric acid hydrolysis under hydrothermal conditions and neutralization with ammonia, compared with only 30.2%, 84.3% and 253.2 C for sulfuric acid hydrolysis, respectively. More importantly, good stability of aqueous CNC suspensions can also be obtained due to the existence of ammonium groups, which can easily be removed through simple heat treatment before using the CNCs.
Functionalized
cellulose nanocrystals (PHCNs) were synthesized by grafting poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
(PHBV) onto cellulose nanocrystals (CNCs). The resultant PHCNs with
high loading levels were uniformly dispersed into a PHBV matrix to
produce fully biodegradable nanocomposites, which showed superior
mechanical performance and thermal stability. Compared with those
of neat PHBV, the tensile strength, Young’s modulus, and elongation
at break of the nanocomposites with 20 wt % PHCNs were enhanced by
113%, 95%, and 17%, respectively. Meanwhile, the initial decomposition
temperature (T
0), temperature at 5% weight
loss (T
5%), maximum decomposition temperature
(T
max), and complete decomposition temperature
(T
f) increased by 29.6, 23.9, 34.7, and
37.0 °C, respectively. This improvement was primarily ascribed
to uniform dispersion of the PHCNs and to strong interfacial adhesion
between filler and matrix due to the chain entanglements, cocrystallization,
and hydrogen bonding interactions. Moreover, the nanocomposites showed
a wider melt-processing window than neat PHBV. Furthermore, the crystallinity
and hydrophilic properties of the nanocomposites could be modulated
through with the increase of the PHCN contents. In addition, the nanocomposites
were nontoxic to human MG-63 cells. Such high performance bionanocomposites
have great potential in expanding the utilization of CNCs from natural
resources and practical application as PHBV-based bioplastic and biomedical
materials.
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