32 research outputs found
Biodegradable starch-based composites: effect of micro and nanoreinforcements on composite properties
Thermoplastic starch (TPS) matrix was reinforced with various kenaf bast cellulose nanofiber loadings (0–10 wt%). Thin films were prepared by casting and evaporating the mixture of aqueous suspension of nanofibers (NFs), starch, and glycerol which underwent gelatinization process at the same time. Moreover, raw fibers (RFs) reinforced TPS films were prepared with the same contents and conditions. The effects of filler type and loading on different characteristics of prepared materials were studied using transmission and scanning electron microscopies, X-ray diffractometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and moisture absorption analysis. Obtained results showed a homogeneous dispersion of NFs within the TPS matrix and strong association between the filler and matrix. Moreover, addition of nanoreinforcements decreased the moisture sensitivity of the TPS film significantly. About 20 % decrease in moisture content at equilibrium was observed with addition of 10 wt% NFs while this value was only 5.7 % for the respective RFs reinforced film
Recent advances and perspectives on starch nanocomposites for packaging applications
Starch nanocomposites are popular and abundant materials in packaging sectors. The aim of this work is to review some of the most popular starch nanocomposite systems that have been used nowadays. Due to a wide range of applicable reinforcements, nanocomposite systems are investigated based on nanofiller type such as nanoclays, polysaccharides and carbonaceous nanofillers. Furthermore, the structures of starch and material preparation methods for their nanocomposites are also mentioned in this review. It is clearly presented that mechanical, thermal and barrier properties of plasticised starch can be improved with well-dispersed nanofillers in starch nanocomposites
Sphaerotilus natans Isolated from Activated Sludge and Its Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
Sphaerotilus natans is a sheathed bacterium existing in the activated sludge of wastewater treatment plants. It is one of the filamentous bacteria causing the bulking and foaming difficulties of activated sludge. Isolating the strain and culturing it in an axenic environment could not only provide the metabolic knowledge of the strains that would be useful in the development of wastewater treatment methods, but also could enable us to gain an understanding of the mechanism by which poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (poly[3-HB-co-3-HV]) is produced by this strain. This article reports the screening and isolation of the strain from the activated sludge using the Nile blue staining method together with Fourier transform infrared analysis. We investigated the ability of the selected strain to produce poly(3-HB-co-3-HV) cop01ymer using glucose and peptone, or by adding valeric acid or sodium propionate as precursor. Proper precursor feeding could dramatically enhance its 3HV content in the copolymer P(3HB-co-3HV). By controlling the different feeding times in fed-batch fermentation, different desired copolymers were obtained with 15, 40, and 70% 3HV mole fraction of the copolymer. Polymer properties were analyzed by gas chromatography, differential scanning calorimetry, thermo-gravimetry, and nuclear magnetic resonance analysis.Department of Applied Biology and Chemical Technolog
Biocomposites from polyhydroxybutyrate and bio-fillers by solvent casting method
Biocomposites from polyhydroxybutyrate (PHB) and some bio-fillers such
as lignin (L), alpha cellulose (AC) and cellulose nanofibrils (CNFs)
were prepared to investigate the effect of the bio-fillers on the
properties of PHB by a solvent casting method. The thermal properties by
thermogravimetry analysis (TGA-DTG and DTA) and differential scanning
calorimetry (DSC) were determined; morphological characterization by
scanning electron microscopy (SEM) and structural analysis by X-ray
diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) of
the biocomposites were performed. TGA curves showed that the highest
values for T-10\%, T-50\% of the biocomposites were 278.2(degrees)C for
PHB+2\%AC and 291.7(degrees)C for PHB+2\%CNFs; however, the best value
for T-75\% was obtained as 381.5(degrees)C for PHB+2\%L. According to
DTG curves, the best results were found for PHB+0.5\%L and
PHB+0.5\%CNFs. DTA showed an increase in temperature of maximum
degradation with loading of lignin and CNFs. The addition of bio-fillers
increases T-c and T-m for both first cooling/heating and second
cooling/heating. T-c and T-m values for first cooling/healing were found
to be lower as compared with second cooling/healing. Furthermore, the
addition of bio-fillers acts as a nucleating agent in PHB and SEM
pictures showed the porous structure in all biocomposites. SEM images
revealed uniform distribution of the reinforcing particles in the
polymer at low loadings (0.5 wt\%), while higher loadings (2 wt\%) of L
and CNFs contributed to easy aggregation within the PHB matrix. In XRD
studies, PHB in the range 5-55 degrees shows 6 main peaks. XRD patterns
of the PHB biocomposites revealed 3 main peaks at 13.57(degrees),
16.87(degrees) and 22.1 degrees, and the other peaks disappeared in the
patterns. The largest and lowest values of X-c were found for PHB+2\%AC
and PHB+2\%CNFs, respectively