Discriminating the viscoelastic properties of cellulose textile fibers for recycling

The viscoelastic properties of cellulose fibers play an important role in chemical recycling of textiles. Here we discriminated the intrinsic viscosity of cotton roll towels and bed linens using near-infrared imaging spectroscopy and supervised pattern recognition. The classification results showed training and test set accuracies of 84–97% and indicated that the relevant spectral features were related to water, cellulose, and cellulose crystallinity. We hypothesized that the decreasing intrinsic viscosity of cotton was associated with changes in cellulose crystallinity and water adsorption, which was supported by additional X-ray and sorption measurements. These results are important as they indicate the potential to non-invasively estimate the degree of polymerization and the suitability of different cotton materials for chemical recycling. We propose that changes in the degree of polymerization and cellulose crystallinity could be used as an indicator of the chemical quality of cellulose fibers, which would have wider impacts for textile recycling.</p

High-quality cellulosic fibers engineered from cotton–elastane textile waste

Even small amounts of elastane in cotton−elastane blended textiles can prevent fiber-to-fiber recycling strategies in textile recycling. Herein, the selective separation of elastane from cotton blends was addressed by the aminolytic degradation of the synthetic component. Polar aprotic solvents were tested as elastane solvents, but side reactions impeded aminolysis with some of them. Aminolysis of elastane succeeded under mild conditions using dimethyl sulfoxide in combination with diethylenetriamine and 1,5-diazabicyclo[4.3.0]non-5-ene as a cleaving agent and catalyst, respectively. The analysis of the nitrogen content in the recovered cellulose fraction demonstrated that 2 h of reaction at 80 °C reduced the elastane content to values lower than 0.08%. The characterization of the recovered cellulose showed that the applied conditions did not affect the macromolecular properties of cellulose and maintained a cellulose I crystal structure. Degraded elastane products were recovered through precipitation with water. Finally, the cellulosic component was turned into new fibers by dry-jet wet spinning with excellent tensile propertiesUniversidade de VigoStrategic Research Council (Finlandia) | Ref. 327298Strategic Research Council (Finlandia) | Ref. 52615Agencia Estatal de Investigación | Ref. RYC2021-033826-IUniversidade de Vigo/CISU

Entwicklung hocheffizienter, γ\gamma-insensitiver Detektormaterialien und Bildplatten für Neutronen

Neutron image plates provide the means for two-dimensional, position-sensitive detection of neutrons. Commercially available neutron image plates consist of a mixture of a neutron converter and storage phosphor dispersed in an organic binder supported by a flexible sheet. The aim of this dissertation was to find a system of converter and storage phosphor which shows a high efficiency for the detection of neutrons while at the same time features a low $\gamma$sensitivity. Additionally, the technology to fabricate neutron image plates based on this system with a spatial resolution of $\le$ 1 mm$^{2}$ was to be developed. In order to reach this aim, first, the storage phsosphors had to be optimised. Investigations on BaFBr:Eu$^{2+}$ have shown that its sensitivity can be raised significantly by doping it with 1 mol% calcium. Additionally, the calcium doping increased the stimulability of the phosphor at the wavelength of 635 nm, which is important for practical applications. It was demonstrated that this increased stimulability is due to a calcium-induced formation of disturbed colour centres, i.e. F$_{A}$(Br$^{-}$, Ca$^{2+}$), whose stimulation maxima are shifted by about 80 nm towards longer wavelengths compared to undisturbed colour centres. Furthermore, the method of linearly modulated photostimulated luminescence (LM-PSL) was used for the first time on BaFBr:Eu$^{2+}$. With this method, which is using a linearly increasing intensity of the stimulatiog light, it was possible to determine the optical cross-sections of the centres responsible for the photostimulated luminescence (PSL). Additionally, the two storage phosphors KCIEu$^{2+}$ and KBr:Eu$^{2+}$ were investigated. It was found that the optimum activator concentration for highest photostimulated luminescence output is 0.05 mol% Eu$^{2+}$. Doping experiments analogous to BaFBr:Eu$^{2+}$ were performed on KCI:Eu$^{2+}$ for the purpose of shifting the stimulation maximum to a longer wavelength and a linear correlation between the maximum and the bromine content was found. However, although the stimulation maximum is shifting in a favourable direction, the doping of KCI:Eu$^{2+}$ with KBr is no feasible or practicable way for a optimisation of this storage phosphor, because the sensitivity of those KCI$_{1-x}$XBr$_{x}$:Eu$^{2+}$ mixed crystals is considerably lower than of KCI:Eu$^{2+}$. Using results from LM-PSL experiments it was possible to show that this reduced sensitivity is not caused by a diminished optical cross-section, i.e. a lower stimulability, but a decreased number of photostimulable centres. Hence, KCI:Eu$^{2+}$ without other dopants was used for all subsequent experiments

Droplet Probe for Characterization of Advancing and Receding Contact Angles of Single Fibers

Characterizing the wetting properties of fibers is crucial for many research and industry applications, including textiles for water-oil separation and composite materials. Those fibers are often soft, typically tens of micrometers in diameter but millimeters in length, making manipulation and characterization difficult. Contact angles of single fibers are usually determined by droplet shape analysis or force-based Wilhelmy method. However, these methods are unable to accurately measure contact angles above 60∘ or ensure reliable control of the liquid-fiber interaction process, especially for soft fibers prone to bending. Consequently, reliable characterization of the advancing and receding contact angles of single fibers remains a challenge. Here we report a novel method for characterizing the advancing and receding contact angles of both soft and rigid single fibers using a millimeter-sized droplet probe affixed to a disk and a numerical model of the system. By analyzing side-view images, we extract key geometrical parameters of the disk-droplet-fiber system, which, when used in detailed simulations, allows estimating the contact angle of fibers ranging from 20∘ to 140∘ . We applied this method to characterize three distinct micro-fibers: a highly hydrophilic rigid borosilicate glass fiber, a mildly hydrophilic soft PET fiber, and a rigid hydrophobic tungsten wire coated with a commercial super-repellent coating.Peer reviewe

Carbon Fibers Based on Cellulose–Lignin Hybrid Filaments: Role of Dehydration Catalyst, Temperature, and Tension during Continuous Stabilization and Carbonization

Lignocellulose has served as precursor material for carbon fibers (CFs) before fossil-based polymers were discovered as superior feedstock. To date, CFs made from polyacrylonitrile have dominated the market. In search of low-cost carbon fibers for applications with medium strength requirements, cellulose and lignin, either as individual macromolecule or in combination, have re-gained interest as renewable raw material. In this study, cellulose with 30 wt% lignin was dry-jet wet-spun into a precursor filament for bio-based carbon fibers. The stabilization and carbonization conditions were first tested offline, using stationary ovens. Diammonium sulfate (DAS) and diammonium hydrogen phosphate were tested as catalysts to enhance the stabilization process. Stabilization is critical as the filaments’ strength properties drop in this phase before they rise again at higher temperatures. DAS was identified as a better option and used for subsequent trials on a continuous carbonization line. Carbon fibers with ca. 700 MPa tensile strength and 60–70 GPa tensile modulus were obtained at 1500 °C. Upon further carbonization at 1950 °C, moduli of >100 GPa were achieved

Development of cellulose films by means of the Ioncell® technology, as an alternative to commercial films

Open Access funding provided by Aalto University. The first stage of this research was founded by Stora Enso Oy, and then by Jenni and Antti Wihuri Foundation (Project Numbers 00210053 and 00220062). Publisher Copyright: © 2023, The Author(s).In recent years, the search for alternatives to petroleum derived products, such as plastic films, has become a priority due to the growing depletion of fossil reserves and the pollution of water resources by microplastics, microscopically small plastic particles which are harmful to ocean and aquatic life. Cellulose-based films, e.g., cellophane and cuprophane, have been on the market for almost a century. Despite being a more ecological option compared to plastic films, the manufacture of these cellulose films involves high production costs and the use of harmful chemicals. As an alternative, a sustainable and eco-friendly process based on the Lyocell-type Ioncell® technology is presented to produce cellulose films. Regenerated cellulose films are created by continuous extrusion via dry-jet wet spinning of an ionic liquid–cellulose solutions. The influence of the polymer concentration (8–13 wt%) and processing temperature (50–100 °C) on the properties of the films were studied by the determination of the thickness, mechanical properties, physical appearance, morphology, chemical composition, and hydrophobicity. The obtained films are thin (12–21 μm), transparent (transmittance = 91%) and of homogeneous structure. Moreover, they exhibit excellent mechanical properties: stress values up to 210 MPa and elongations up to 19% in machine (longitudinal) direction. These values clearly outperform commercial cellophane, which presents stress values of 125 MPa and elongations of 22%. The films presented herein hold great potential to become an eco-friendly and sustainable option to commercial films.Peer reviewe