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Fibers, Volume 10, Issue 11 (November 2022) – 9 articles

Cover Story (view full-size image): Vegetable fibres are a sustainable alternative to non-natural fibre-reinforced concrete (FRC). The main issues in regard to plant-based fibres are their properties’ variability and potential high biodegradability in the alkaline pH of concrete. Aiming to minimise the variability of flax and hemp fibres, this study evaluates a range of chemical surface treatments’ effects on the behaviour of fibres used for FRC. A treatment using NaOH 10% for 24 h enhanced the properties of hemp FRC and reduced the degradability in an alkaline solution. For flax fibres, a novel alternative stood out: a treatment using 1% of stearic acid in ethanol for 4 h increased the tensile by 101%, with a minor effect on the elastic modulus. FRC with the treated flax fibres reduced thermal conductivity as well as the elastic modulus, and increased residual tensile strength in addition to fracture energy. View this paper
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25 pages, 8237 KiB  
Article
Suitability of Surface-Treated Flax and Hemp Fibers for Concrete Reinforcement
by Ana Caroline da Costa Santos and Paul Archbold
Fibers 2022, 10(11), 101; https://doi.org/10.3390/fib10110101 - 17 Nov 2022
Cited by 5 | Viewed by 2711
Abstract
The use of vegetable fibres as a sustainable alternative to non-natural sources of fibres applied for concrete reinforcement has been studied for over three decades. The main issues about plant-based fibres pointed out by other authors are the variability in their properties and [...] Read more.
The use of vegetable fibres as a sustainable alternative to non-natural sources of fibres applied for concrete reinforcement has been studied for over three decades. The main issues about plant-based fibres pointed out by other authors are the variability in their properties and concerns about potential high biodegradability in the alkaline pH of the concrete matrix. Aiming to minimise the variability of flax and hemp fibres, this research compares a range of chemical surface treatments, analysing their effects on the behaviour of the fibres and the effects of their addition to concrete. Corroborating what has been found by other authors, the treatment using NaOH 10% for 24 h was able to enhance the properties of hemp fibre-reinforced concrete and reduce the degradability in alkaline solution. For flax fibres, a novel alternative stood out: treatment using 1% of stearic acid in ethanol for 4 h. Treatment using this solution increased the tensile by 101%, causing a minor effect on the elastic modulus. Concrete mixes reinforced with the treated flax fibres presented reduced thermal conductivity and elastic modulus and increased residual tensile strength and fracture energy. Full article
(This article belongs to the Special Issue Plant Fibers II)
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16 pages, 3541 KiB  
Article
Permeable Membranes PUR/TETA and PUR/TEPA for CO2 Capture Prepared with One-Step Electrospinning Technology
by Jakub Hoskovec, Pavla Čapková, Monika Vostiňáková, Petr Ryšánek, Pavel Kaule, Jonáš Tokarský, Oldřich Benada and Vratislav Blechta
Fibers 2022, 10(11), 100; https://doi.org/10.3390/fib10110100 - 16 Nov 2022
Cited by 2 | Viewed by 2296
Abstract
A simple one-step technology of wire electrospinning is presented for the manufacturing of air-permeable CO2-capturing membranes, easily transferable to industrial production lines. The design of the chemically-modified polyurethane nanofiber membranes for CO2 capture was based on a combination of molecular [...] Read more.
A simple one-step technology of wire electrospinning is presented for the manufacturing of air-permeable CO2-capturing membranes, easily transferable to industrial production lines. The design of the chemically-modified polyurethane nanofiber membranes for CO2 capture was based on a combination of molecular modeling and technological experiments using one-step electrospinning (i.e., a modifying agent dissolved directly in a spinning solution). Polyurethane (PUR Larithane), chemically modified by TETA/TEPA amines, was used in the present study for the membrane design. Special attention was paid to two key parameters significant for the design of the functional unit, i.e., the CO2 sorption capacity and air permeability which depended on the amine concentration. The optimal combination of these parameters was found for the PUR/TEPA membrane (5 wt.% of TEPA in spinning solution): the sorption capacity was 13.97 cm3/g with an air permeability of 0.020 m/s. Molecular modeling proved to be a valuable tool that helped to clarify, at the molecular level, the structure of chemically-modified nanofibrous membranes. Full article
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17 pages, 4187 KiB  
Article
Influence of Abaca Fiber Inclusion on the Unconfined Compressive Strength of Reconstituted Sandy Silts
by Jorge Albuja-Sánchez, Eduardo Alcívar, Daniela Escobar, Juan Montero, Guillermo Realpe, Andrés Muñoz and Mateo Peñaherrera-Aguirre
Fibers 2022, 10(11), 99; https://doi.org/10.3390/fib10110099 - 12 Nov 2022
Cited by 1 | Viewed by 2224
Abstract
The present investigation determines the influence of abaca (Musa textilis) fiber inclusion on the simple compressive strength of reconstituted sandy silt specimens. For this purpose, fibers of different lengths (5, 10 and 15 mm) and quantities (0.5, 1.0, 1.5 and 2.0% of soil [...] Read more.
The present investigation determines the influence of abaca (Musa textilis) fiber inclusion on the simple compressive strength of reconstituted sandy silt specimens. For this purpose, fibers of different lengths (5, 10 and 15 mm) and quantities (0.5, 1.0, 1.5 and 2.0% of soil dry weight) are added to produce the reconstituted specimens. Subsequently, the physical and mechanical behavior of soil–fiber mixtures were evaluated through compaction and unconfined compression tests. The experimental results showed that increases in fiber content or length, or both, led to a 1235.1% increase in maximum compression stress (compared to the fiber-free soil). Compression failure occurred at a greater axial strain when 10 and 15 mm fibers were added at 1% dosage or in percentages equal to or greater than 1.5% regardless of fiber length. A series of linear mixed models identified statistically significant effects of fiber length and percentage on the level of effort and on the unitary deformation. Full article
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8 pages, 1870 KiB  
Article
Ultrashort Pulse Retrieval from Experimental Spectra Transformed in Chalcogenide and Silica Fibers
by Elena A. Anashkina, Arseny A. Sorokin and Alexey V. Andrianov
Fibers 2022, 10(11), 98; https://doi.org/10.3390/fib10110098 - 11 Nov 2022
Cited by 2 | Viewed by 1405
Abstract
The characterization of ultrashort optical pulses is a highly requested task. The most popular commercially available hardware/software systems are based on interferometric measurements and second-harmonic generation, leading to some ambiguities and limitations. Here we experimentally test the non-interferometric method of pulse retrieval from [...] Read more.
The characterization of ultrashort optical pulses is a highly requested task. The most popular commercially available hardware/software systems are based on interferometric measurements and second-harmonic generation, leading to some ambiguities and limitations. Here we experimentally test the non-interferometric method of pulse retrieval from three spectra: the fundamental spectrum and two spectra that transformed in an element with Kerr nonlinearity and accumulated different nonlinear phases (different Β-integrals). This method has no ambiguities related to time direction, and allows simple hardware/software implementation. We test a novel simple algorithm for experimental data processing based on the search for a polynomial-approximated spectral phase. Two experimental cases are considered. In the first one, we retrieved 160 fs pulses using a chalcogenide arsenic sulfide glass fiber as a nonlinear Kerr element. In the second case, we retrieved 670 fs pulses with a complex spectrum using a piece of silica-based fiber. The results are confirmed by independent measurements using a standard SHG-FROG technique (Second-Harmonic Generation Frequency-Resolved Optical Gating). Full article
(This article belongs to the Special Issue Fiber Laser Sources II)
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22 pages, 6564 KiB  
Technical Note
Analysis of Adhesive Distribution over Particles According to Their Size and Potential Savings from Particle Surface Determination
by Jan T. Benthien, Jördis Sieburg-Rockel, Nick Engehausen, Gerald Koch and Jan Lüdtke
Fibers 2022, 10(11), 97; https://doi.org/10.3390/fib10110097 - 11 Nov 2022
Cited by 3 | Viewed by 2192
Abstract
Wood and its processing into particles are, combined, the largest cost factor in the production of particleboard, followed by the cost of adhesive. Thus, reducing their cost is a goal of process optimization. This study investigated whether possible savings could be identified and [...] Read more.
Wood and its processing into particles are, combined, the largest cost factor in the production of particleboard, followed by the cost of adhesive. Thus, reducing their cost is a goal of process optimization. This study investigated whether possible savings could be identified and quantified by determining the particle surface using automated three-dimensional laser-scanning technology (3D Particleview, Fagus-Grecon). The focus was on saving adhesive by sieving out adhesive-consuming fines. It was shown that, currently, with the actual prices for wood (89 €/t), particle preparation (37 €/t), and adhesive (570 €/t), the resulting additional costs for particles are overcompensated by the savings for adhesive with high adhesive content (e.g., 19%). The assumption of uniform distribution of adhesive on the total surface of all particles was checked for correctness using digital reflected light microscopy (VHX-5000, Keyence). Since urea-formaldehyde (UF) adhesive commonly used in particleboard production can only be detected with increased effort, phenol-formaldehyde (PF) adhesive was applied for the tests. Ultraviolet microspectrophotometry (UMSP) was used to rule out excessive penetration of the adhesive into the wooden tissue of the particles. The examination of the distribution of the adhesive over the surface showed that smaller particle sizes tended to be more heavily coated with adhesive. This means that the calculated savings still underestimate the real-life potential or that potential savings exist even with lower adhesive prices or higher prices for wood. Full article
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12 pages, 1533 KiB  
Article
Coconut-Fiber Composite Concrete: Assessment of Mechanical Performance and Environmental Benefits
by Emilio Vélez, Ricardo Rodríguez, Nicolay Bernardo Yanchapanta Gómez, Edgar David Mora, Luis Hernández, Jorge Albuja-Sánchez and María Inés Calvo
Fibers 2022, 10(11), 96; https://doi.org/10.3390/fib10110096 - 9 Nov 2022
Cited by 5 | Viewed by 4017
Abstract
The purpose of this qualification work is to study the physical and mechanical behavior of concrete with the addition of 0.5% and 1% coconut fiber, which has been subjected to two chemical treatments to reduce its degradation. The coconut fibers were extracted from [...] Read more.
The purpose of this qualification work is to study the physical and mechanical behavior of concrete with the addition of 0.5% and 1% coconut fiber, which has been subjected to two chemical treatments to reduce its degradation. The coconut fibers were extracted from the raw material and cut into pieces 4 cm long. Subsequently, the fibers were subjected to two chemical treatments. The first involved immersing the fibers in 4% sodium hydroxide (NaOH) solution, and the second treatment involved coating them with gum arabic and silica fume. A total of 50 samples of fibers were collected in their natural and post-treated state to be tested. The dosage was prepared for design strengths of 210 and 240 kg/cm2 (20.59 and 23.54 MPa), so that the percentages of 0.5% and 1% volume of coconut fiber, for the two treatments selected, replaced the respective volume of coarse aggregates. The cylinders with 1% addition of fibers had the best performance for the design strength of 20.59 MPa, including the cylinders without fibers. Those with 0.5% addition of fibers presented better performance for the 23.54 MPa dosage, although this was lower than the cylinders without fibers. In all cases, the cylinders with NaOH-treated fibers outperformed their counterparts with fibers treated with gum arabic and silica fume. Finally, a CO2 balance was determined, and an environmental gain up to 14 kg in CO2 emissions was established for each cubic meter of composite concrete. Full article
(This article belongs to the Special Issue Natural Fiber Competitiveness and Sustainability)
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15 pages, 5624 KiB  
Article
Preparation of Side-By-Side Bicomponent Fibers Using Bio Polyol Based Thermoplastic Polyurethane (TPU) and TPU/Polylactic Acid Blends
by Jiyeon Oh, Young Kwang Kim, Sung-Ho Hwang, Hyun-Chul Kim, Jae-Hun Jung, Cho-Hyun Jeon, Jongwon Kim and Sang Kyoo Lim
Fibers 2022, 10(11), 95; https://doi.org/10.3390/fib10110095 - 9 Nov 2022
Cited by 7 | Viewed by 2751
Abstract
In this study, side-by-side bicomponent fibers were prepared by melt spinning using bio-based thermoplastic polyurethane (TPU) and TPU/polylactic acid (PLA) blends. The morphology, thermal and mechanical properties of the fibers were investigated. To this end, the synthesis of TPU using biomass-based polyols and [...] Read more.
In this study, side-by-side bicomponent fibers were prepared by melt spinning using bio-based thermoplastic polyurethane (TPU) and TPU/polylactic acid (PLA) blends. The morphology, thermal and mechanical properties of the fibers were investigated. To this end, the synthesis of TPU using biomass-based polyols and the preparation of TPU/PLA blends were preceded. Their morphological and structural characteristics were investigated. The synthesis of TPU was confirmed through Fourier transform infrared analysis, and as a result of gel permeation chromatograph analysis, a compound having a weight average molecular weight of 196,107 was synthesized. The TPU/PLA blends were blended in the ratio of 80/20, 60/40, 40/60, and 20/80 through a melt extruder. They formed a sea–island structure as a result of scanning electron microscope analysis, and an increase in the PLA content in the TPU matrix caused a decrease in the melt flow index. Finally, TPU/(TPU/PLA) side-by-side bicomponent fibers were prepared by utilizing the above two materials. These fibers exhibited tensile strengths of up to 3624 MPa, with improved biocarbon content of up to 71.5%. These results demonstrate the potential of TPU/(TPU/PLA) side-by-side bicomponent fibers for various applications. Full article
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13 pages, 1709 KiB  
Review
Invasive Alien Plant Species for Use in Paper and Packaging Materials
by Urška Vrabič-Brodnjak and Klemen Možina
Fibers 2022, 10(11), 94; https://doi.org/10.3390/fib10110094 - 31 Oct 2022
Cited by 10 | Viewed by 3940
Abstract
Invasive plant species can impede the establishment and growth of native plants and affect several ecosystem properties. These properties include soil cover, nutrient cycling, fire regimes, and hydrology. Controlling invasive plants is therefore a necessary, but usually expensive, step in restoring an ecosystem. [...] Read more.
Invasive plant species can impede the establishment and growth of native plants and affect several ecosystem properties. These properties include soil cover, nutrient cycling, fire regimes, and hydrology. Controlling invasive plants is therefore a necessary, but usually expensive, step in restoring an ecosystem. The sustainability of materials with an emphasis on the use of local resources plays an important role in the circular economy. The use of alternative fibers from invasive plants promotes local production in smaller paper mills that offer the protection of local species and the reduction of waste and invasive plants. A synthesis of the literature is needed to understand the various impacts of invasive plants and their practical control in the context of papermaking applications and to identify associated knowledge gaps. To improve our understanding of the practical application of invasive species in the paper industry, we reviewed the existing literature on invasive plant species in the area of fiber production, printability, coating solution production, dyes, and extracts, and collected information on the major invasive plant species in Europe and the methods used for various applications. Full article
(This article belongs to the Collection Review Papers of Fibers)
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24 pages, 22504 KiB  
Article
Numerical Study of the Performance of Existing Prestressed Cylindrical Concrete Pipes Strengthened with Reinforced Concrete or Carbon-Reinforced Fiber Polymer Jackets—Part B
by Konstantinos Katakalos, Lazaros Melidis, George Manos and Vassilios Soulis
Fibers 2022, 10(11), 93; https://doi.org/10.3390/fib10110093 - 28 Oct 2022
Cited by 1 | Viewed by 1660
Abstract
A popular water pipe system, used in many countries, is one formed by prestressed cylindrical concrete pipes (PCCP). This study used the results of an experimental investigation on ten (10) PCCP samples taken from an existing water pipeline. The objective was to investigate [...] Read more.
A popular water pipe system, used in many countries, is one formed by prestressed cylindrical concrete pipes (PCCP). This study used the results of an experimental investigation on ten (10) PCCP samples taken from an existing water pipeline. The objective was to investigate their bearing capacity under three-edge bending or internal hydraulic pressure loads to check the capability of specific retrofitting/strengthening schemes to upgrade this bearing capacity and thus enhance the operational period (Part A). In this part B study, the measured response of the PCCP pipes was made to validate a numerical approach aimed at numerically simulating the behavior of the original and retrofitted PCCP pipes under hydraulic internal pressure. From the obtained numerical results, it was seen that the assumed nonlinear mechanisms for the concrete volume and steel membrane were verified by comparing numerical predictions with measurements in terms of strain response of the steel membrane, damage patterns of the concrete volume, and the overall internal pressure versus radial expansion response. The numerical predictions of the bearing capacity contribution of the fully active prestress as well as the three specific jacketing schemes, including carbon fiber reinforced polymer (CFRP) or reinforced concrete (RC) jackets, were also verified from comparisons with the corresponding measured response. Full article
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