Fibers, Volume 10, Issue 5 (May 2022) – 9 articles

We report on the synthesis of titanium dioxide by titanium carbide for the preparation of hybrid material reinforced with polyaniline (PANI@TiO₂–TiC) using the in situ polymerization technique. The effectiveness of the samples on the thermal, optical and electrochemical properties was investigated. The XRD, XPS, FTIR, SEM and TEM results confirm the successful synthesis of the PANI, PANI@TiC and PANI@TiO₂–TiC samples. Through this, a good connection, an excellent relationship between the structures and the properties of the synthesized hybrid materials were obtained. Moreover, the electrical conductivity and optical bandgap were also tested. Remarkably good electrochemical characteristics were identified by cyclic voltammetry. Moreover, the galvanostatic charge–discharge (GCD) of the supercapacitor was remarkably high. Cyclic stability showed good retention after 1500 cycles at 1.5 A·g⁻¹. Full article

The production of long flax fiber for the subsequent production of textile yarn is accompanied by the formation of a significant amount of waste—noils, which is a mechanical mixture of long and short flax fibers and shives. Comparative studies of the structure and chemical composition of the fibrous fraction of noils and shives were carried out using IR spectroscopy. The solubility of shives and flax noils in N-methylmorpholine-N-oxide (NMMO) was studied, a comparative analysis of the rheological behavior of solutions of flax and wood cellulose was carried out and the optimal temperature–concentration conditions for obtaining flax fibers from noils were determined. It was shown for the first time that using the method of solid-phase activation of the cellulose-solvent system makes it possible to obtain fibers in a short period of time (no more than 10 min). The structure of both the raw material and the resulting fibers was studied by X-ray diffraction analysis. The thermal properties of a new type of cellulose fibers was evaluated. The complex of the conducted studies allows us to consider flax fibers from noils along with flax fibers from long-staple flax, as a real alternative to fibers from wood pulp. Full article

Renders should have an adequate resistance to impacts, since they must protect the substrate. The use of fibres may enhance the energy absorbed when the mortars are submitted to an impact load, which contributes to postpone the first crack, and control its propagation and width. In this study, the impact strength was measured by a falling mass from different heights. The cracking pattern and the impact energy for the appearance of the first crack and until failure were evaluated. An artificial accelerated ageing test was also performed, and the impact resistance was analysed before and after ageing. In order to analyse the effects of recycled fibres, wool, coir, flax and textile-acrylic waste fibres were used as reinforcement in cement and cement-lime mortars. The results indicated that the fibres’ addition significantly improved the impact energy of the rendering mortars in comparison with the reference mortars. Concerning the crack patterns, the recycled fibres prevented the opening or the growth of the cracks, before and after ageing. This effect is mainly due to the fibre’s bridge mechanism, due to crossing the open cracks and hindering their propagation. The fibres’ type, length and volume fraction have influenced the mortars’ performance in terms of impact resistance. Textile-acrylic fibres waste presented the best performance by comparison with the natural fibres used. Full article

Natural-fiber-reinforced composites are seen as a good alternative to traditional synthetic-fiber composites. However, to successfully implement these materials in engineering applications, along with these materials demonstrating satisfactory load-bearing capacity, it is necessary to provide engineers with effective material properties, as well as calculation methods that take into account the distinctive features of natural fibers. This study investigated the effective elastic properties and strength of materials composed of unidirectional sisal fibers within a thermosetting polymer matrix, containing 20%, 40% and 60% fiber-volume fraction. Experiments with axial and off-axis loads in conjunction with finite-element modeling were utilized to determine the effective mechanical response of the composites. Analytical and numerical models were considered, using both isotropic- and anisotropic-fiber approaches. It is shown that only by taking into account the sisal-fiber anisotropy can the experimental results of the off-axis experiments be reproduced. The influence of sisal-fiber transverse modulus on the overall mechanical response is a function of the sisal-fiber volume fraction. It has been shown that the longitudinal specific strength of sisal-fiber-reinforced composites is comparable to classical aluminum alloys or steel. Thus, this environmentally friendly composite can be considered as an alternative in some engineering applications, such as reinforcement in concrete composites. Full article

The article at hand is envisaged to enumerate significant technological parameters for the successful impregnation of carbon fiber rovings having 50,000 (50 K) filaments, each within a fine-grained, cementitious suspension. Parameters such as the number of rollers as well as the influence of roller deflection and rotation have been investigated and discussed with regard to the quality of the related impregnation and mechanical properties resulting therefrom. Morphological analysis disclosed distinct differences in the fiber matrix distribution, which are particularly reflected in the flexural performance of the mineral-impregnated carbon fibers (MCFs) produced. Moreover, with the best fiber matrix distribution, uniaxial tensile tests on MCFs demonstrated superior tensile strengths, moduli of elasticity, and elongations at rupture. Full article

Natural fibers have recently been presented as a promising alternative for manufactured fibers. Date palm fibers showed interesting results when used as an inclusion in concrete and mortar. In this study, Sefri Date Palm Mesh Fibers (SDPMF) were used as an inclusion in mortars. Silica fume (SF) partially replaced the cement by 5%, 10%, 15%, and 20% by mass to improve the mechanical properties of SDPMF mortars. SDPMFs were collected from local farms. The fibers were then cleaned, dried, and cut to 50 mm, and added to mortars with 1%, 2%, and 3% by weight. Density, absorption, open porosity, workability, and compressive strength of mortars were investigated. A comparison with a previous study’s results for mortars containing Sefri Date Palm Leave Fibers (SDPLF) is presented. The results showed that the incorporation of SF as part of cement may lead to improving the properties of the mixtures containing SDPMF fibers. Full article

Reactive chemical modifications have been shown to impart decay resistance to wood. These modifications change hydroxyl availability, water uptake, surface energy, and the nanostructure of wood. Because fungal action occurs on the micro and nano scale, further investigation into the nanostructure may lead to better strategies to prevent fungal decay. The aim of this article is to introduce our findings using small angle neutron scattering (SANS) to probe the effects of chemical modifications on the nanostructure of wood fibers. Southern pine wood fiber samples were chemically modified to various weight percentage gains (WPG) using propylene oxide (PO), butylene oxide (BO), or acetic anhydride (AA). After modification, the samples were water leached for two weeks to remove any unreacted reagents, homopolymers or by-products and then the equilibrium moisture content (EMC) was determined. Laboratory soil-block-decay evaluations against the brown rot fungus Gloeophyllum trabeum were performed to determine weight loss and decay resistance of the modifications. To assist in understanding the mechanism behind fungal decay resistance, SANS was used to study samples that were fully immersed in deuterium oxide (D₂O). These measurements revealed that modifying the fibers led to differences in the swollen wood nanostructure compared to unmodified wood fibers. Moreover, the modifications led to differences in the nanoscale features observed in samples that were exposed to brown rot fungal attack compared to unmodified wood fibers and solid wood blocks modified with alkylene oxides. Full article

Recently, a novel corrosion-resistant construction material, Carbon Concrete Composite (C³), consisting of coated carbon fibers embedded in a concrete matrix, was introduced. However, thermal exposure during domestic fires may impact the release of organic pollutants and fibers during abrasive processing and/or demolition. Consequently, the objective of this study was to explore the emission characteristics of toxic compounds and harmful fibers during the dry-cutting after exposure to 25–600 °C (3 h, air). These parameters mimic the abrasive machining and dismantling after a domestic fire event. Mass spectrometry and chromatography served as analytical methodologies, and no organic pollutants for exposure temperatures ≥ 400 °C were found. In contrast, significant amounts of pyrolysis products from the organic fiber coating were released at lower temperatures. Studying the morphology of the released fibers by electron microscopy revealed a decrease in fiber diameter for temperatures exceeding 450 °C. At ≥550 °C, harmful fibers, according to the World Health Organization (WHO) definition, occurred (28–41 × 10³ WHO fibers/m³ at 550–600 °C). This leads to the conclusion that there is a demand for restraining and protection measures, such as the use of wet cutting processes, suction devices, particle filtering masks and protective clothing, to handle thermally stressed C³. Full article

Corrosion study of conventional reinforcement in concrete has been accorded wider importance in the last few decades based on the losses occurring in monitoring concrete structures. It is well known that the presence of chloride ions is one of the most significant factors contributing to the corrosion of reinforcing steel. Practically, it is observed that in the marine environment, the activating substances such as chlorides that penetrate the steel can counteract the passivity locally when the electrolyte is highly alkaline. The concrete cover is changed chemically when chloride ionspenetrate into the material, whereupon the pore solution is neutralized. Based on numerous studies, it is evident that steel fibers and glass fibers have less impact on cracked sections in a chloride environment and can oppose chloride infiltration. Glass fibers, when exposed to repeated freeze and thaw conditions, protect the passive layer. This review article highlights the corrosion behavior of reinforced concrete involving various factors such as cracking behavior, transportation, electric conductivity, resistivity, and diffusion of chloride ions in the presence of steel and glass fibers. Full article