The characteristics and properties of bacterial cellulose and dialdehyde celluloses from
bacterial cellulose were studied by XRD, TG-IR and adsorption capacity testing. The crystal cell
parameters of BC were calculated and approximated to that of monocline crystal cell model. The
XRD profiles showed that the crystallinity degree of BC was 66%, and that of the DACs (12%
aldehyde) was 56%. The optimal adsorption capacities of pure water on dried BC and DAC were 12
g/g and 3.1 g/g respectively, and that of iron ion on dried BC and DAC were 11 mg/g and 6.9 mg/g
respectively. And the optimal adsorption capacity of hexanediamine on DAC was 700 mg/g, and
that of n-phenylene diamine on DAC was 490 mg/g. The IR result showed that the adsorption of
hexanediamine on DAC was physical adsorption, not chemical reaction under the experimental
conditions.
This paper addresses the determination of aldehyde group (% of dialdehyde units) in dialdehyde cellulose (DACs) oxidized from bacterial cellulose (BC). With 4 determination methods, the oxidation degrees of DACs were studied: Automatic potential titration method through Schiff base reaction, Acid-base titration in Cannizzaro reaction, Metaperiodate consumption determination, and Measurement of amino nitrogen content in DAC derivatives. By comparing determination results of these methods, we found out the proper way suitable for this metaperiodate oxidation system of BC to measure the dialdehyde unit content of the DACs.
A series of dialdehyde cellulose samples with varied aldehyde content were prepared by oxidation of bacterial cellulose with sodium periodate. The X-ray diffractometry profile showed that the crystallinity degree of bacterial cellulose was 66%, but that of the dialdehyde cellulose (containing 12% aldehyde ) was 56%. Thermal decomposition of these dialdehyde cellulose samples and bacterial cellulose were studied by thermogravimetry. The decomposition of bacterial cellulose in nitrogen started at 230 and rapid weight loss occurred between 300-400. The introduction of dialdehyde group to bacterial cellulose resulted in significant shifts of decomposition to lower temperature range. The decomposition of dialdehyde cellulose (12% aldehyde ) started at 180 and rapid weight loss between 200-350. The temperature of rapidest weight loss shifted from 340 of bacterial cellulose to 290 of the dialdehyde cellulose(12% aldehyde).
Bacterial cellulose-poly (ethylene glycol) composites (BC-PEG) were biosynthesized by adding different molecular weight of poly (ethylene glycol) into Acetobacter xylimum culture medium. The obtained BC-PEG composites were characterized by scanning electron microscopy (SEM), thermogravimetry (TG), X-ray diffractometry (XRD) and tensile test. SEM images showed that the morphology of BC-PEG composites changed. TG results indicated their thermal stability also changed. XRD profiles suggested their crystalline morphology no much difference. But the tensile tests appeared that the adding of different molecular weight PEG modified the mechanical properties of BC-PEG composites.
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