Fibers2014, 2(4), 295-307; doi:10.3390/fib2040295 - published 13 November 2014 Show/Hide Abstract
Abstract: Smart multi-walled carbon nanotube (MWCNT)-coated cellulose fibers with a unique sensing ability were manufactured by a simple dip coating process. The formation of electrically-conducting MWCNT networks on cellulose mono- and multi-filament fiber surfaces was confirmed by electrical resistance measurements and visualized by scanning electron microscopy. The interaction between MWCNT networks and cellulose fiber was investigated by Raman spectroscopy. The piezoresistivity of these fibers for strain sensing was investigated. The MWCNT-coated cellulose fibers exhibited a unique linear strain-dependent electrical resistance change up to 18% strain, with good reversibility and repeatability. In addition, the sensing behavior of these fibers to volatile molecules (including vapors of methanol, ethanol, acetone, chloroform and tetrahydrofuran) was investigated. The results revealed a rapid response, high sensitivity and good reproducibility for these chemical vapors. Besides, they showed good selectivity to different vapors. It is suggested that the intrinsic physical and chemical features of cellulose fiber, well-formed MWCNT networks and favorable MWCNT-cellulose interaction caused the unique and excellent sensing ability of the MWCNT-coated cellulose fibers, which have the potential to be used as smart materials.
Fibers2014, 2(4), 285-294; doi:10.3390/fib2040285 - published 27 October 2014 Show/Hide Abstract
Abstract: Cellulose deposition in developing cotton fibers has been studied previously with analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), High-performance liquid chromatography (HPLC) and Thermogravimetric analysis (TGA). Recent technological developments in instrumentation have made Raman microscopy emerge as an extraordinary analytical tool in biological and plant research. The advantage of using confocal Raman microscopy (CRM) resides in the lateral spatial resolution and in the fact that Raman spectroscopy provides not only chemical composition information, but also structural information. Cross-sections of cotton fibers harvested at different developmental stages were studied with CRM. The Raman bands assigned to cellulose were analyzed. The results of this study indicate that CRM can be used as a tool to study cellulose deposition in cotton fibers and could provide useful information on cellulose deposition during cotton fiber development.
Fibers2014, 2(4), 275-284; doi:10.3390/fib2040275 - published 21 October 2014 Show/Hide Abstract
Abstract: Hybrid sols of poly (vinyl alcohol) (PVA)/Silicon oxide-titanium oxide (SiO2-TiO2) were prepared with tetraethoxylsilane and tetrabutyl titanate as precursor using Sol-Gel method. PVA/SiO2-TiO2 hybrid fibers were prepared by drawing from the hybrid sols using dip-coating method and aging treatment. The spinnability of hybrid sols was investigated. Spinnable time (t) and spinnable length (l) of hybrid sols increased with either the PVA content or the molar ratio of SiO2 and TiO2. The hybrid fibers were characterized by Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), X-ray diffraction (XRD), Ultraviolet Visible Spectrometry (UV-Vis) and (Thermo-gravimetric Analysis) TGA. FT-IR results suggested that PVA was linked with (SiO2-TiO2) network by chemical bonds. SEM measurements indicated that when the fibers arrives the maximum spinning length, the diameter of the fibers was about 50 μm, and the whole system was homogeneous. XRD results revealed that the crystallinity of hybrid fibers was decreased distinctly. UV-Vis measurements confirmed that the shielding properties to Ultraviolet (UV) were greatly improved with titania filled in the hybrid fibers. TG measurements suggested that the hybrid fibers show better resistance to heat than pure PVA fibers.
Fibers2014, 2(4), 264-274; doi:10.3390/fib2040264 - published 29 September 2014 Show/Hide Abstract
Abstract: Cotton is and has been a large cash crop in the United States and abroad for many years. Part of the widespread interest and utility of this product is due to its attractive chemical and physical properties for use in textiles. The textile industry could benefit from the presentation of a quick, reliable method to classify U.S. from foreign cottons so that the appropriate tariffs can be levied for non-American cottons. In addition, there is some interest in avoiding cotton identity theft. Thus, an accurate and precise instrumental method would be of interest to correctly identify the country of origin of cotton. This study provides an analytical method to identify domestic and foreign cotton fibers using near-infrared (NIR) spectroscopy coupled with principal component analysis (PCA). Samples from American cottons were evaluated along with a representative amount of international samples. The results provide a proof of concept that indicates that PCA analysis can be used to separate the respective domestic and foreign cotton groups.
Fibers2014, 2(3), 255-263; doi:10.3390/fib2030255 - published 22 September 2014 Show/Hide Abstract
Abstract: A (1→3)-β-d-Glucan produced by Lactobacillus suebicus CUPV221 strain was investigated by tapping mode atomic force microscopy (TM-AFM), to compare its supramolecular structure and conformation with two commercial polysaccharides: curdlan and scleroglucan. It was found that the β-d-Glucan was a (1→3)(1→2)-β-d-Glucan and at room temperature formed three-dimensional networks by entanglements between strands, as does scleroglucan. However, (1→3)(1→2)-β-d-Glucan strands seemed to be more stiff than those of scleroglucan. It was also observed that curdlan samples deposited from 5 mM NaOH aqueous solution showed supermolecular assemblies, recognized in the literature as micelles, which are controlled by hydrophobic hydration. The (1→3)(1→2)-β-d-Glucan in alkaline aqueous solutions produced different supramolecular structures depending on pH, and at 0.4 M NaOH (pH 13.16), denaturation took place. After neutralizing the alkaline solution with HCl, the formation of short linear, circular, and hairpin structures was observed.
Fibers2014, 2(3), 242-254; doi:10.3390/fib2030242 - published 22 August 2014 Show/Hide Abstract
Abstract: The objective of this research was to evaluate the properties of the chemically retted kenaf bast fiber impregnated with the inorganic nanoparticles. High quality kenaf bast fibers were obtained from a chemical retting process. An in situ inorganic nanoparticle impregnation (INI) process was used to introduce the CaCO3 nanoparticles into the retted kenaf bast fibers. It was found that some of the lignin-based components in the retted fibers were further removed during the INI treatment. From the characterization results, the inorganic nanoparticles CaCO3, with different shapes and sizes, appeared at the surface of the impregnated fiber after treatment. Heterogeneous CaCO3 nanoparticle distribution was observed on the INI treated fibers. The CaCO3 contents were different at different locations along the impregnated fiber. The presence of CaCO3 inorganic nanoparticles at the fiber surface increased the root mean square (RMS) surface roughness by 5.8% and decreased the hydrophilic nature of the retted fibers, evidenced by a 59.4% decrease in adhesion force between the fiber and hydrophilic AFM tip. In addition, the impregnation of CaCO3 dramatically increased the Young’s modulus of the fiber by 344%.