Gum Arabic (GA) collected from Acacia senegal trees was used with polyvinyl alcohol (PVA) to prepare of a series of biodegradable membranes doped and non-doped with potassium dichromate (K 2 Cr 2 O 7 ). Adding the K 2 Cr 2 O 7 to the GA/PVA blends slightly decreased their crystallinity index (CI) by about 2 %. Increasing the PVA concentration in the chromated GA/PVA blends was responsible for increasing the CI. Adding the K 2 Cr 2 O 7 to the pure GA solution modified its differential thermal behavior whereby the exothermic reactions occurred between 321°C and 433°C were disappeared. The K 2 Cr 2 O 7 increased the heat change drastically for all the bioplastic blends with the highest increase for the pure GA. Adding K 2 Cr 2 O 7 to the pure PVA increased the nanometric particle size (NPS) significantly. Increasing the PVA concentration in a blend had a greater effect than did the K 2 Cr 2 O 7 on the NPS. The buried bioplastic membranes in the control soil had different count and species of microbial communities. The numbers of bacteria and fungi in the initial soil sample were lower than those for chromated GA membranes and were greater than those for the chromated PVA. All bacterial and fungi species had growth ability and are expected to be detoxification tools of chromium ion-doped blends of GA and PVA leading to a green environment.
Cellulose nanocrystals (SCNCs) were synthesized from macerated fibers isolated from leaflets of date palm (Phoenix dactylifera L.). The resultant SCNCs were characterized by optical, scanning and transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). H 2 SO 4 -hydrolysis helped isolation of SCNCs with high crystallinity by removing the amorphous regions of the cellulosic microfibril. The SCNCs in an acidic solution were aggregated to form bigger architectures. The SCNCs exhibited a principle sharp peak around 2θ = 21.25° related to the cellulose-I structure. The crystallinity index of the SCNCs was found to be high (85.5%). The average crystallite size of the SCNCs was 2.7 nm. The FTIR results confirmed high purity of the SCNCs conforming to cellulose I. The TGA showed that about 59.13% of the SCNCs mass was lost up to 500°C. Based on the results, the leaflets are suitable precursor for SCNCs synthesis.
In this paper, crude flakes (CFs) of shellac were converted into purified, nonwoven, thermospun fibers (shellac floss) using two devices, namely, an electric thermospinner (ETS) and a microwave thermospinner (MTS). This conversion was achieved by the action of heating and the centrifugal forces that arose toward the outside of the spinner-head cavity. The dissolved MTS floss was bleached using hydrogen peroxide to produce the bleached MTS floss. The unbleached shellac (CFs, ETS floss, and MTS floss) and the bleached MTS floss were characterized physically and chemically. There was no deterioration in the floss properties due to the heating tools or bleaching process. For the unbleached shellac, although there were no statistical differences in properties among the three shellac types (CFs, ETS floss, and MTS floss), except for insolubility in hot alcohol, acid value, and moisture content, the MTS floss exhibited superior values compared with the other types for nearly all the properties studied. Bleaching the MTS floss produced the greatest color change among other studies, caused a high reduction in insoluble solid matter due to increasing the solubility of some of the solid constituents of shellac, and slightly decreased its Young’s modulus (E). The important dental applications were surveyed and it was suggested that the suitability was enhanced by using the bleached MTS floss, based on its superior whiteness, along with the unique properties detected.
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