Dwarf-green coconut fibers: A versatile natural renewable raw bioresource. Treatment, morphology, and physicochemical properties

Dwarf-green coconut fibers were modified by alkali treatment and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), as well as thermogravimetric (TGA), mechanical, and dielectric analyses. Changes in composition, structure, and morphology of the coconut fibers were observed after sodium hydroxide treatments due to the removal of lignin, hemicellulose, and other impurities. The XRD data were in agreement with the morphological analysis, where the crystallinity fraction increased with the concentration of alkali solution and fell off above 10%. The infrared spectrometry showed the partial dissolution of hemicellulose, lignin, and pectin, which was clearly identified by the band at 1736 cm-1. Thermogravimetric analysis showed a double degradation process for the untreated dwarf-green coconut fibers, while a single one was observed after the pretreatment. The tensile properties showed an increased elongation at break, modulus, and strength, and the dielectric results showed a decrease of all parameters (permittivity, dielectric loss, and conductivity), reflecting the reduced dipole and ion mobility associated with the loss of amorphous components

Investigation of AC-Measurements of Epoxy/Ferrite Composites

A pure ferrite and epoxy samples as well as the epoxy/ferrite composites with different 20 wt.%, 30 wt.%, 40 wt.%, and 50 wt.% weight ferrite contents have been prepared by the chemical co-precipitation method. AC-conductivity and dielectric properties such as the dielectric constant and dielectric loss of the prepared samples have been studied. The obtained results showed that the samples had a semiconductor behavior. The dielectric constant of the composites has been calculated theoretically using several models. For the composite sample that contains 20 wt.% of ferrites, these models give satisfactory compliance, while for the composite samples with a higher percentage of nanofillers, more than 30 wt.% theoretical results do not coincide with experimental data. The investigated polymer has very low conductivity, so this type of polymer can be useful for high-frequency applications, which can reduce the losses caused by eddy current. Thus, the prepared samples are promising materials for practical use as elements of microwave devices