Wettability Of Fibers Research Articles

Repair of road surfaces using cold wet fiber containing asphalt concrete mixtures

During the construction of experimental sections of road surfaces in v. Ust-Kurdyum of the Saratov district of the Saratov region has been established the efficiency of production and application of cold fiber-containing dispersed-reinforced asphalt concrete mixtures with dispersed bitumen. A method for accelerating the formation of the structure of cold fiber-containing asphalt concrete by heat treatment of its surface is studied. Dispersed bitumen after drying the water film has good adhesion to concrete, asphalt concrete and other materials. The asphalt concrete formed as a result of curing on the basis of dispersed bitumen is high-strength, chemical-resistant, hydrophobic and environmentally friendly, corresponding to the existing regulatory requirements for asphalt concrete. For the production of asphalt mixtures, mass-produced equipment is suitable using materials commonly used in hot asphalt concrete: crushed stone, sand, mineral powder and bitumen. Operations on drying and heating of crushed stone and sand are excluded from the technological process. Asphalt concrete mix does not stick to the surface of rubberized rollers of vibratory rollers, which allows compacting mixtures with a high content of mineral powder at any time. There are fewer cracks on the surface of the compacted layer than when using a smooth-rolling roller. The technology is recommended for extended use on roads and streets of localities, and highways with low traffic intensity.

Electrospun PCL/PGS Composite Fibers Incorporating Bioactive Glass Particles for Soft Tissue Engineering Applications.

Poly(glycerol-sebacate) (PGS) and poly(epsilon caprolactone) (PCL) have been widely investigated for biomedical applications in combination with the electrospinning process. Among others, one advantage of this blend is its suitability to be processed with benign solvents for electrospinning. In this work, the suitability of PGS/PCL polymers for the fabrication of composite fibers incorporating bioactive glass (BG) particles was investigated. Composite electrospun fibers containing silicate or borosilicate glass particles (13-93 and 13-93BS, respectively) were obtained and characterized. Neat PCL and PCL composite electrospun fibers were used as control to investigate the possible effect of the presence of PGS and the influence of the bioactive glass particles. In fact, with the addition of PGS an increase in the average fiber diameter was observed, while in all the composite fibers, the presence of BG particles induced an increase in the fiber diameter distribution, without changing significantly the average fiber diameter. Results confirmed that the blended fibers are hydrophilic, while the addition of BG particles does not affect fiber wettability. Degradation test and acellular bioactivity test highlight the release of the BG particles from all composite fibers, relevant for all applications related to therapeutic ion release, i.e., wound healing. Because of weak interface between the incorporated BG particles and the polymeric fibers, mechanical properties were not improved in the composite fibers. Promising results were obtained from preliminary biological tests for potential use of the developed mats for soft tissue engineering applications.

Effect of Power Ultrasonic on the Expansion of Fiber Strands

The present study investigates the effect of power ultrasonic on the expansion of fiber strands. A potential application of such expansion is in the production process known as closed injection pultrusion. The fiber strand in the pultrusion injection chamber is in compacted form, and so, any expansion of the fiber strand resulting from power ultrasonic should lead to improved fiber wetting. To investigate this, a wetted fiber strand was clamped on two sides and sonicated in the middle from below. The potential expansion of the fiber strand was visually determined through an observation window. The study concluded that power ultrasonic has a minimal to virtually negligible effect on the expansion of both glass and carbon fiber. The degree of expansion remains within a range of 3% maximum, with a standard deviation in the respective midpoint tests of up to 60% for glass fiber and over 100% for carbon fiber. This shows that the fibers are limited in their freedom of movement, and so no expansion can be achieved using power ultrasonic. A further increase in amplitude does not lead to any further expansion but to the destruction of the fibers.

Investigation of the Influence of PLA Molecular and Supramolecular Structure on the Kinetics of Thermal-Supported Hydrolytic Degradation of Wet Spinning Fibres.

In this study, differences in the kinetics of the thermal-supported hydrolytic degradation of polylactide (PLA) wet spinning fibres due to material variance in the initial molecular and supramolecular structure were analysed. The investigation was carried out at the microstructural and molecular levels by using readily available methods such as scanning electron microscopy, mass erosion measurement and estimation of intrinsic viscosity. The results show a varying degree of influence of the initial structure on the degradation rate of the studied PLA fibres. The experiment shows that hydrolytic degradation at a temperature close to the cold crystallization temperature is, on a macroscopic level, definitely more rapid for the amorphous material, while on a molecular scale it is similar to a semi-crystalline material. Furthermore, for the adopted degradation temperature of 90 °C, a marginal influence of the pH of the degradation medium on the degradation kinetics was also demonstrated.

The impact of hydrothermal carbonization on the surface functionalities of wet waste materials for water treatment applications

Hydrothermal carbonization (HTC) is an energy-efficient thermochemical process for converting wet waste products into value added materials for water treatment. Understanding how HTC influences the physicochemical properties of the resultant materials is critical in optimizing the process for water treatment, where surface functionality and surface area play a major role. In this study, we have examined the HTC of four wet waste streams, sewage sludge, biosludge, fiber sludge, and horse manure at three different temperatures (180 °C, 220 °C, and 260 °C). The physicochemical properties of these materials were examined via FTIR, SEM and BET with their adsorption capacity were assessed using methylene blue. The yield of solid material after hydrothermal carbonization (hydrochar) decreased with increasing temperature for all samples, with the largest impact on horse manure and fiber sludge. These materials also lost the highest degree of oxygen, while HTC had minimal impact on biosludge and sewage sludge. The differences here were due to the varying compositions of each waste material, FTIR identified resonances related to cellulose in horse manure and fiber sludge, which were not detected in biosludge and sewage sludge. Adsorption capacities varied between 9.0 and 68 mg g−1 with biosludge HTC at 220 °C adsorbing the highest amount. Adsorption also dropped drastically at the highest temperature (260 °C), indicating a correlation between adsorption capacity and HTC conditions. This was attributed to the loss of oxygen functional groups, which can contribute to adsorption. These results suggest that adsorption properties can be tailored both by selection of HTC temperature and feedstock.

Improving the Tensile Properties of Wet Spun Silk Fibers Using Rapid Bayesian Algorithm.

Wet spinning of silkworm silk has the potential to overcome the limitations of the natural spinning process, producing fibers with exceptional mechanical properties. However, the complexity of the extraction and spinning processes have meant that this potential has so far not been realized. The choice of silk processing parameters, including fiber degumming, dissolving, and concentration, are critical in producing a sufficiently viscous dope, while avoiding silk's natural tendency to gel via self-assembly. This study utilized recently developed rapid Bayesian optimization to explore the impact of these variables on dope viscosity. By following the dope preparation conditions recommended by the algorithm, a 13% (w/v) silk dope was produced with a viscosity of 0.46 Pa·s, approximately five times higher than the dope obtained using traditional experimental design. The tensile strength, modulus, and toughness of fibers spun from this dope also improved by a factor of 2.20×, 2.16×, and 2.75×, respectively. These results represent the outcome of just five sets of experimental trials focusing on just dope preparation. Given the number of parameters in the spinning and post spinning processes, the use of Bayesian optimization represents an exciting opportunity to explore the multivariate wet spinning process to unlock the potential to produce wet spun fibers with truly exceptional mechanical properties.

Ultrafast Self-Propelled Directional Liquid Transport on the Pyramid-Structured Fibers with Concave Curved Surfaces

Self-propelled directional liquid transport (SDLT) has been observed on many natural substrates, serving as an efficient strategy to utilize surrounding liquids for a better habitat to the local environment. Drawing inspiration, various artificial materials capable of SDLT have been developed. However, the liquid transport velocity is normally very low (ca. 3-30 μm/s), which limits its practical applications. Herein, we developed novel pyramid-structured fibers with concave curved surfaces (P-concave curved-fiber, PCCF), which enable the ultrafast SDLT. Specifically, the liquid transport velocity can be up to ∼28.79 mm/s on a dry tri-PCCF, over 50 times faster than that on the surface of Sarracenia trichome (∼520 μm/s). The velocity is even faster on a wet fiber by two times (∼47.34 mm/s). Here, the Laplace pressure difference (FL) induced by the tapered structure determines the liquid transport direction. It is proposed that both the capillary rises imparted by the concave curved surfaces and the oriented microridges/valleys and the enhanced FL aroused by the reduced cross-sectional area accelerate the SDLT on surfaces of the PCCFs. Consequently, the PCCF takes a different liquid transport strategy with a convex-shaped advancing meniscus, differing from that on traditional conical fibers. Moreover, the as-developed PCCF is also applicable for underwater ultrafast SDLT of oil. We envision that the result will open a new perspective for fabricating a fibrous system for microfluidic and liquid manipulation.

Natural fiber reinforced inorganic foam composites from short hemp bast fibers obtained by mechanical decortation of unretted stems from the wastes of hemp cultivations

The wettability of hemp fibers, to be applied in fiber-reinforced foams, can be improved with several chemical treatments. In this paper, a innovative treatment with sodium ascorbate was evaluated. Untreated and treated fibers have been characterized using FTIR spectroscopy and TGA measurements. Furthermore, the feasibility of treated fibers was evaluated preparing diatomite-based fiber-reinforced foams. These materials were finally characterized by mechanical compressive strength and thermal properties (thermal conductivity). The fiber-reinforced foams have been produced using a diatomite natural source as a matrix. A suitable amount of Si powder and vegetable surfactant were used as chemical and physical foaming agents while a polysilicate solution was used as reactive crosslinker. The foams highlight low density, around 350 kg/m3, and low thermal conductivity (0.06 W/mK).

Fiber tortuosity and its effects on shock transfer characteristics of Ultra High Molecular Weight Polyethylene (UHMWPE) fibers embedded in a polyurethane composite structure

Low density, high strength, and flexibility of ultra-high molecular weight polyethylene (UHMWPE) fibers have made them a topic of intensive research in many fields. More specifically, UHMWPE has been extensively used in shock damping applications. However, little is known about the effects of fiber tortuosity and fiber wetting on the shock transfer characteristics of these fibers. Herein, focus is placed on studying the effects of tortuosity and fiber wetting on the shock transfer characteristics of UHMWPE fiber braid embedded in a polyurethane matrix. Shock transfer characteristics of these fibers are identified by generating a longitudinal shock on one end of the fiber, while simultaneously measuring the transferred force overtime on the other side of the fiber. From the experiments it is found that the force versus time response of these structures show an underdamped response. Analyzing the maximum force transfer and the rate of decay, it is seen that tortuosity has a significant effect on the shock transfer characteristics of these structures. Given the nature of these results, it is strongly believed that the presented work provides a creative strategy for designing, developing, and characterizing, new composite structures with improved impact attenuation characteristics.

THE INFLUENCE OF SURFACE DESTRUCTION ON THE HYDROPHILICITY AND ABILITY TO FORM CONNEC-TIONS OF THE CELLULOSE FIBERS

When using cellulose fibers to produce paper, the main role is played by the state of the surface of the fiber and its ability to adhesive-cohesive interaction. The main indicators characterizing the surface of the fiber are development and roughness, chemical heterogeneity, depending on the presence of various functional groups, as well as structural heterogeneity of the surface layers, leading to the formation of a stronger bond between the fibers. The surface modification of the fiber was carried out by partial acid hydrolysis. The study is aimed at optimizing hydrolysis, choosing methods for its control, obtaining physicochemical and physicomechanical characteristics of partially hydrolyzed cellulose, and increasing the ability to bind cellulose fiber. A method has been developed for producing modified cellulose with improved adhesion-cohesive properties by surface destruction of wet cellulose fibers during hydrolysis. The patterns of activation of the surface properties of cellulose fibers are obtained. The effect of partial acid hydrolysis on the development of the surface of the fiber in the absence of "wet" grinding with water shortage is shown. The effect of short chains and reducing carbonyl groups of cellulose macromolecules on the binding capacity of modified cellulose has been established. The optimal content of short chains of cellulose macromolecules, which is 12%. Such a content of short chains of modified fibers by acid hydrolysis was detected at a temperature of 363 K and an exposure time of 40 s; under these optimal conditions, the strength of the experimental castings increases by 70%.

On increasing wet-web strength with adhesive polymers

Fiber-fiber adhesion, called “bonding” in the old paper physics literature, is a critical component of the overall strength of dry paper. With freshly formed very wet pulp fiber webs, all evidence suggests there are no fiber-fiber crossings with significant adhesive joint strength. With water removal, a point will be reached where fiber-fiber adhesion starts to contribute to the overall wet-web strength. The literature reveals very few examples of polymers that increase fiber-fiber joint strength in freshly formed webs. Here, we summarize the literature and explain why it is so difficult to promote fiber-fiber wet adhesion with polymers. Nevertheless, ongoing research in areas as diverse as tissue engineering scaffolds and biomimetic adhe-sives gives clues to future developments. Advances in paper machine engineering have lessened the importance of wet-web strength. By contrast, a critical issue in many of the evolving nanocellulose technologies is the strength of objects first formed by aqueous processing, the green strength—the strength of wet bodies before drying. For exam-ple, 3-D printed nanocellulose objects and ultralow density cellulosic aerogels can be destroyed by capillary forces during drying. There is a need for adhesives that strengthen freshly formed, wet lignocellulosic joints.

Numerical simulation of mesoscopic bubble defect and optimization of process parameters in fiber wetting process of high voltage post insulator resin

Based on the method of fluid volume function, the two-phase flow model of mesoscopic resin and air between unit cell fiber bundles was established. The causes of mesoscopic bubble defects were discussed and the controllable process parameters were analyzed. A near-real mono-cell mesoscopic geometry model of strut insulator was constructed and meshed. The solution of the resin and air two-phase flow model was completed by adopting the finite volume method and using the Fluent software. The numerical simulation of the mesoscopic resin air two-phase flow and the air bubble defect was applied. The relationship between process parameters and air bubble defect was studied, and process parameters were optimized. Through the contrastive analysis of the capillary number, the correctness of the numerical simulation and parameter optimization was theoretically verified. Further, the effectiveness of the method in this paper was verified through the experiment.

A Qualitative Analysis of Different Types of Water Repellent Agent Used on Cotton Fabric

The existence of intermolecular attractive forces of polarity and hydrogen bond is imperative in providing strength, heat resistance and drycleaning resistance to cotton fabric. However, these forces enhance easy wetting of fiber by water offering little resistance to snow and rain for outerwear garments. This problem could be overcome by adding water repellent chemicals to the fabric either chemically or with mechanical coating which prevent penetration of water through the fabric without destroying comfort of the fabric. The aim of the work is to evaluate the effect of different types of water repellent agents used on cotton fabric and analyze different possible factors affecting the performance and quality of treated fabrics. For this purpose, three water repellent chemicals: Lurotex protector RP ECO is a product based on C6 technology, Rucostar EEE6 product consists of a hydrocarbon matrix and hyper-branched, star-shaped polymers(dendrimers) and Nuva TTC is a conventional fluorocarbon based water repellent chemicals were used in three different concentrations to find out an optimum chemical concentration. To judge the quality of the treated fabrics, spray test, air permeability test, strength test and abrasion resistance test were evaluated. The quality of treated fabrics for all three chemicals was very close to each other and if the process parameters is maintained successfully, desired results can be achieved.

Effect of plasma treatment on chemical composition, structure and sorption properties of lignocellulosic hemp fibers (Cannabis sativa L.)

Hemp fibers with different amount of hemicelluloses and lignin were subjected to atmospheric pressure dielectric barrier discharge under different conditions (40 W and 80 W power of discharge, const. time 120 s) in order to study influence of plasma treatment on their structure and sorption properties. Wettability of plasma treated samples, compared with precursors, increased due to the changes in hemp fiber surface chemistry confirmed by ATR FTIR spectroscopy and increased roughness as a consequence of intensive surface etching, observed by SEM. After plasma treatment, wettability was the highest for hemp fibers with lower content of hemicelluloses (increase up to 9 times), while wettability of raw hemp fibers and fibers with lower content of lignin increased about 5 and 2 times, respectively. This investigation shows that plasma can be successfully used for improvement of raw hemp fibers wettability, even to substitute the chemical treatment for some applications of hemp.

Electro-bending behavior of curved natural fiber laminated composites

Experiments are performed to understand the electro-bending behavior of conductive jute/epoxy curved composites for monitoring of damage under four-point bending. A well-connected electrical network in the laminated curved composite is obtained by wet flocking micro carbon fibers between laminates and dispersing carbon nanotubes (CNTs) within the matrix. By embedding only 0.1 wt% of CNTs into the composites, the effects of carbon fiber length and density on electro-bending behavior is studied. The normalized curved beam strength (curved beam strength/thickness) of composites marginally increased for a case of carbon fiber length of 350 µm and fiber density of 500 fibers/mm2 compared to composites with no carbon fibers, however for all other cases, it showed slight decrease. The electro-bending behavior of composites of carbon fiber length of 150 µm showed higher percentage resistance change both at crack initiation point as well as at failure of specimen compared to those of carbon fiber length of 350 µm. The longer fiber (350 µm) composites provided rich conductive network and formed new connections to compensate the increase in resistance due to damage growth.

Vinylester / glass fiber interface: Still a key component for designing new styrene-free SMC composite materials

Sheet molding compounds (SMC) allow to design high performance polymer-matrix composites increasingly used for structural applications in the automotive industry. SMC are usually based on an unsaturated polyester thermosetting resin diluted in styrene with chopped glass fibers and fillers. Due to international regulations linked with the potential risks of styrene, replacing such styrene-based reactive system compound is becoming more and more strategic in order to zero-VOC emission, while keeping similar (or displaying even better) mechanical properties and shrinkage control to conventional SMC-based composite materials. In this study, the same sized E-glass fiber was combined with two different vinylester matrices, a conventional styrene containing resin and a styrene free one. The second type fits more suitable for friendly environmentally purposes as it is based on a dimethacrylate diluent. The objective of this work is focused on interfacial adhesion in both systems as the fiber/matrix interface is a key parameter governing the mechanical properties of the final composite materials. A multiscale analysis was carried out from: i)the fiber scale by measuring the interfacial shear stress by using the microdebonding test; ii)the fibers bundle scale by studying the wettability of fibers by the uncured resin; iii)up to the mechanical characterization of unidirectional SMC composites by measuring the interlaminar shear strength (ILSS). As main results, it is demonstrated that the styrene-free composites have a suitable interfacial resistance compared to conventional systems whereas impregnation, i.e. specific fiber sizings which will be more soluble in the resin-dimethacrylate reactive system need to be designed.

An effective surface modification of UHMWPE fiber for improving the interfacial adhesion of epoxy resin composites

AbstractUltra high molecular weight polyethylene (UHMWPE) fiber composite was reinforced by coating a functional layer on the surface of the UHMWPE fiber to improve interfacial adhesion between the fiber and the resin matrix. In this work, tannic acid (TA)‐Na+ composite modified UHMWPE fiber was used to improve moisture wettability and adhesion between the fiber and the resin. This approach had the advantages of being green, sustainable, lossless, low‐cost, and industrialized. The surface characteristics of UHMWPE fiber were investigated by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The results show that the TA coating can improve the surface roughness, wettability, and adhesion of UHMWPE fiber, thereby improving the interface properties between fiber and resin. The tensile strength of interfacial shear strength and macro‐composites of TA coating UHMWPE fiber increased by 43.3% and 28%, respectively.

Thermal treatment as an effective method of carbon/glass fibers surface modification for high-performance thermoplastic polymer matrix composites

Fiber reinforced high-performance thermoplastic polymer composites are one of the most promising materials in modern materials science. At the same time the challenges with high processing temperatures and melt viscosity, poor interfacial adhesion has slowed adoption of this materials. Most commonly used as reinforcements carbon and glass fibers are usually has an inert surface that prevent good wettability and formation of strong fiber–matrix interface. In this work, thermal treatment of carbon and glass fibers was used as a method of the fibers’ surface modification. A polyethersulfone (PES) based composites reinforced with initial and modified carbon and glass fibers were developed using solution impregnation method followed by compression molding technique. Mechanical and thermal behavior of the composites before and after the modification was studied. It was shown that thermal treatment of the fibers results in improved interfacial interaction as well as higher strength-elastic properties of the PES based composites.

Interface modification of carbon fiber reinforced epoxy composite by hydroxyl/carboxyl functionalized carbon nanotube

Carbon fiber reinforced epoxy (CE) composites are already in extensive use as structural materials in aerospace and marine applications owing to their inherent high specific strength. This study proposes to further improve their mechanical properties by incorporating Hydroxyl/Carboxyl functionalized carbon nanotube (CNT-OH/CNT-COOH) nanofiller onto the surface of carbon fiber. Mechanical properties of CE composites are a strong function of interfacial bond strength between carbon fiber and epoxy matrix. In this regard, improvement of the wettability of fibers by Electrophoretic deposition technique (EPD) is proposed to enhance the interfacial bond strength and hence the properties. CNT-OH/CNT-COOH nanofiller was incorporated onto carbon fibers via EPD technique, maintaining fixed concentration of nanofiller in the bath at constant current and deposition time. Uniform deposition of nanofiller onto the carbon fibers was confirmed by Field Emission Scanning Electron Microscopy (FESEM) studies. The nanofiller deposited carbon fibers were then used for the preparation of composites by hand layup technique. This laminate was subjected to 3-point bend test for estimation of flexural properties. It was reported that CNT-COOH-CE composite exhibited an increase of flexure strength by 10% and 7% when compared to unmodified CE and CNT-OH-CE composites respectively. To evaluate the effect on glass transition temperature (Tg), Differential scanning calorimetry (DSC) was used. Also, the mode of failure in these composites were examined by fractographic study.

Thermo-Stamping Process of Glass and Carbon-Fibre Reinforced Polymer Composites

In this work, manufacturing tools for thermoplastic (TP) composites have been developed. The chosen process involves the stacking alternately of oriented dry fabrics and TP films and does not use semi-products in order to reduce material costs. This study was specifically directed towards optimizing the impregnation of continuous glass and carbon fibres reinforcing two TP amorphous matrices, the polyphenylsulfone (PPSU) and polyetherimide (PEI), to obtain semi-finished products employed for aeronautical structures. The impregnation quality of inter and intra-yarns is analyzed and validated by optical and scanning micrographic observations conducted with an optical and a Scanning Electron Microscopies (SEM), respectively. The study showed that besides the process parameters and porosity distribution in the core of warp yarns, the impregnation quality depends on the surface properties of constituents. Desizing treatment has been carried out to improve the wettability of fibres by the TP matrices.