Wettability Of Fibers Research Articles

Plastic deformation of the microfibrils in wet polyacrylonitrile fibers induced by the stretching field

AbstractThe plastic deformation of the microfibrils governs the formation and development of orientation, crystallization, and structural defects in polyacrylonitrile (PAN) fibers due to the flow‐fiber coupling effect during stretching process. In this study, we investigated the morphological changes of microfibrils in PAN fibers during wet‐fiber stretching using ultrathin section technology and electron microscopy observation. Their plastic deformation mechanism was also revealed. An interconnected network was formed and separated by the pore/voids during coagulation process. Stretching forces facilitated the plastic deformation of microfibrils, resulted in their elongation and orientation. Moreover, the inter‐fibril distance reduced and pore/void shape and dimensions were changed. The distinct response of microfibril elements under stretching force resulted in skin‐core structures within the fiber. Tensile strength increased from 27 to 382 MPa, while elongation at break decreased from 225% to 28%. Aligned microfibrils exhibited high tensile strength, whereas unoriented microfibrillar networks showed relatively high elongation properties. Additionally, we proposed a relationship between microfibril morphology changes and fiber mechanical properties.

A fast and effective way to measure the inner pore size distributions of wetted cotton fibers and their pretreatment performance using time-domain nuclear magnetic resonance

This study reports the findings from using time-domain nuclear magnetic resonance (TD-NMR) to analyze the pore structures of cotton fibers. Cotton fibers, which swell and soften in water, present challenges for conventional pore measurement techniques. TD-NMR overcomes these by measuring the transverse relaxation time (T2) of water protons within the fibers, indicative of internal pore sizes. We established a T2-to-pore size conversion equation using mixed cellulose ester membranes. This enabled differentiation between strongly bound, loosely bound, and free water within the fibers, and detailed the water distribution. A method for measuring the pore size distribution of wet cotton fiber was developed using TD-NMR. We then examined how various pretreatments affect the fibers' internal pores by comparing their pore size distribution and porosity. Specifically, caustic mercerization primarily enlarges the porosity and size of larger pores, while liquid ammonia treatment increases porosity but reduces the size of smaller pores. This research confirms TD-NMR's utility in assessing cotton fabrics' wet processing performance.

A Water-Soluble Thermoplastic Polyamide Acid Sizing Agents for Enhancing Interfacial Properties of Carbon Fibre Reinforced Polyimide Composites.

Carbon-fiber-reinforced polyimide (PI) resin composites have gained significant attention in the field of continuous-fiber-reinforced polymers, in which the interfacial bonding between carbon fiber and matrix resin has been an important research direction. This study designed and prepared a water-soluble thermoplastic polyamide acid sizing agent to improve the wettability of carbon fiber, enhance the van der Waals forces between carbon fiber and resin and strengthen the chemical bonding between the sizing agent and the alkyne-capped polyimide resin by introducing alkyne-containing functional groups into the sizing agent. This study found that the addition of a sizing layer effectively bridged the large modulus difference between the fiber and resin regions, resulting in the formation of an interfacial layer approximately 85 nm thick. This layer facilitated the transfer of stress from the matrix to the reinforced carbon fiber, leading to a significant improvement in the interfacial properties of the composites. Adjusting the concentration of the sizing agent showed that composites treated with 3% had the best interfacial properties. The interfacial shear strength increased from 82.08 MPa to 108.62 MPa (32.33%) compared to unsized carbon fiber. This research is significant for developing sizing agents suitable for carbon-fiber-reinforced polyimide composites.

Designing an End Effector and a Thickness Adaptive Compression Molding Process for Wet Fiber Placement

Designing an End Effector and a Thickness Adaptive Compression Molding Process for Wet Fiber Placement

Semi-theoretical compression model of wet fiber web for the prediction of airflow rate in vacuum dewatering process of papermaking

This study expands the investigation of a mathematical method for predicting the airflow rate during the vacuum dewatering process of papermaking based on our previous research. By integrating poroelastic theory and initial saturation thickness, based on experimental data with a range of 20–60 kPa pressure difference and 20-200 g · m − 2 basis weight, a mathematical method with a semi-theoretical model for compression characteristics of the wet fiber web, the poroelastic porosity model (PEPM), was developed to support and expand on our previously established empirical model for porosity variations in wet fiber web, the variable porosity model (VPM). The accuracy of the mathematical method with the PEPM in predicting the airflow mass flux passing through the wet fiber web was validated using experimental data with a range of 0–60 kPa pressure difference and 20-200 g · m − 2 basis weight. The mean relative errors with the PEPM within the pressure difference range of 0-20 kPa and 0-60 kPa were 7.68% and 8.80%, respectively, compared to 17.44% and 11.67% for those with the VPM, demonstrating the improved applicability and generalization of the mathematical method, particularly in the zone of low pressure difference exceeding the range of the modeling experimental data. The PEPM effectively revealed the strain hardening behavior during the compression process and the diminishing returns of energy in the vacuum dewatering process with an increasing pressure difference. The developed mathematical method with the PEPM for the compression characteristics of the wet fiber web provides an effective and accurate way to predict the airflow rate during the vacuum dewatering process of papermaking.

Influence of duoplasmatron ion source plasma treatment on multi-axial knitted structure reinforced glass fiber composites

The present study investigates the impact of glow discharge cold plasma-induced duoplasmatron ion source on the mechanical properties of multi-axial knitted structure reinforced glass fiber composites. Analysis of failure location and mode in bending tests was conducted using the acoustic emission method. The results reveal that the tensile and bending strength of the multi-axial structure reinforced glass fiber composites treated with oxygen/nitrogen plasma had increased by 21.84% and 37.28%, respectively. In contrast, when treated with oxygen/argon plasma, the corresponding enhancements were 17.47% and 24.16%, respectively. These results indicate that oxygen/nitrogen plasma treatment yields superior mechanical properties to oxygen/argon treatment. The accumulated acoustic emission energy in the multi-axial structure reinforced glass fiber composites subjected to oxygen/nitrogen and oxygen/argon treatments was 25.49% and 62.39% lower than untreated samples, respectively. The failure mode observed in the untreated composites was matrix cracking, whereas the composites treated with dual plasma exhibited interface debonding. The dual plasma modification enhanced fiber wettability and surface roughness, facilitating increased contact area between the fiber and matrix and promoting the overall bonding performance between the two components. Taken together, our findings suggest that duoplasmatron ion source treatment enhanced the interface bonding and mechanical properties of the multi-axial structure reinforced glass fiber composites.

Preparation and good antibacterial properties of self-assembled P(AA-AM)/CA/GA fiber membrane by electrospinning

To reduce mortality rate caused by life-threatening bacterial infections, advanced antibacterial materials have attracted widespread attention from researchers worldwide. In this study, the antibacterial P(AA-AM)/CA/GA nanofiber membranes with pH-responsive properties were successfully prepared by facile electrospinning technology. A series of characterizations of the obtained nanofiber membranes showed the addition of P(AA-AM) improves the surface wettability of the as-spun fibers in comparison to those of CA and CA/GA nanofiber membranes. High-temperature treatment was found to enhance the mechanical properties of the P(AA-AM)/CA/GA membranes due to the crosslinking reactions. The prepared P(AA-AM)/CA/GA nanofiber membrane exhibits a pH-responsive effect which is evident by the change in GA’s release rate in solutions with different pH values. The cellulose acetate (CA) spinning nanofiber structure formed by P(AA-AM) coated GA also extended the release process of GA and improved the antibacterial timeliness of nanofiber membranes. The antibacterial experiments on E. coli and S. aureus showed that the electrospun nanofiber membranes containing GA had potent antibacterial properties, which were further enhanced by increasing the GA content in the P(AA-AM)/CA/GA blends. This study provides an insight into the design and preparation of pH-sensitive antibacterial materials using facile electrospinning technology.

Influence of seawater immersion on acrylic adhesive properties and bond strength on wet composites

This paper describes a study on an acrylic based adhesive developed for marine repair applications. The adhesive alone was aged for over 12 months and tensile samples were tested periodically to characterize the influence of seawater aging at 40 °C. The adhesive alone plasticizes in seawater, losing around 40 % of both modulus and strength after 12 months, but these are largely recovered after drying. In parallel, adhesively bonded glass and carbon fibre composite assemblies were tested after similar aging times. Both retain over 80 % of unaged apparent shear strength after 12 months in natural seawater at 40 °C. Adhesive bonding of wet composite substrates, which had been immersed in seawater for up to 12 months before bonding, was also evaluated to determine residual bond strength. The break strengths of assemblies of wet glass fibre composites were not affected by substrate immersion for up to 12 months before bonding, while strengths of carbon fibre composite assemblies dropped to around 50 % after prolonged substrate immersion. Reasons for this difference are discussed. The results suggest that this adhesive shows good durability and should be considered for marine repair applications.

Droplet Morphology-Based Wettability Tuning and Design of Fog Harvesting Mesh to Minimize Mesh-Clogging.

Fog harvesting relies on intercepting atmospheric or industrial fog by placing a porous obstacle, for example, a mesh and collecting the deposited water. In the face of global water scarcity, such fog harvesting has emerged as a viable alternative source of potable water. Typical fog harvesting meshes suffer from poor collection efficiency due to aerodynamic bypassing of the oncoming fog stream and poor collection of the deposited water from the mesh. One pestering challenge in this context is the frequent clogging up of mesh pores by the deposited fog water, which not only yields low drainage efficiency but also generates high aerodynamic resistance to the oncoming fog stream, thereby negatively impacting the fog collection efficiency. Minimizing the clogging is possible by rendering the mesh fibers superhydrophobic, but that entails other detrimental effects like premature dripping and flow-induced re-entrainment of water droplets into the fog stream from the mesh fiber. Herein, we improvise on traditional interweaved metal mesh designs by defining critical parameters, viz., mesh pitch, shade coefficient, and fiber wettability, and deducing their optimal values from numerically and experimentally observed morphology of collected fog water droplets under various operating scenarios. We extend our investigations over a varying range of mesh-wettability, including superhydrophilic and hydrophobic fibers, and go on to find optimal shade coefficients which would theoretically render clog-proof fog harvesting meshes. The aerodynamic, deposition, and overall collection efficiencies are characterized. Hydrophobic meshes with square pores, having fiber diameters smaller than the capillary length scale of water, and an optimal shade coefficient are found to be the most effective design of such clog-proof meshes.

Investigation of the Relationship between the Energy Characteristics of Phases (Reinforcing Fibers and Binder) and Wettability of Filler in Hybrid Polymer Composite

The study of issues related to the development of a scientifically substantiated method of obtaining hybrid polymer composites (containing more than one type of reinforcing continuous fiber) in order to improve the stiffness characteristics of the material is an urgent task of building materials science, allowing to expand the field of effective application of polymer composites for structural purposes. Wetting of reinforcing fibers with binders during the fabrication of composites largely determines the occurrence of adhesive bonding. In this study it is revealed that wettability correlates with energy characteristics of phases (reinforcing fibers and binder); dispersion parameters of free surface energy of carbon and glass fibers without oiling composition and apprette, parameters of free surface energy of fibers with oiling compositions and apprettes are determined; wetting of fibers by epoxy resins with determination of their surface tension, parameters of free surface energies at the boundary with air is studied; the question of the separation of fibers from air is investigated.

Experimental Study on the Effect of Steel Reinforcement Ration on the Cracking Behaviour of FRP-Strengthened RC Elements

This paper examines the cracking behaviour of reinforced concrete beams strengthened by externally bonded fiber-reinforced polymer. The crack opening of RC structures is a key parameter for the durability of concrete structures. It is of vital importance for designers to be able to make correct estimations of the crack opening values of strengthened structures. FRP strengthening affects the cracking behaviour of RC beams with different steel percentages. Beams have been tested under four-point bending mechanical tests until failure with three steel ratios and two layers of externally bonded wet carbon fibers (CFRP). In order to measure the crack opening during loading, Digital Image Correlation is used to obtain the crack opening along the beam during load functioning. The results allow for a comparison of the RC beams with and without FRP and enhance the effect of FRP on crack opening. The crack width was compared with the theoretical values obtained based on the relation proposed by Eurocode 2 (EC2). The comparison enhanced the need to propose a modified relation. Subsequently, an empirical model was established as a modification of EC2, considering the presence of a CFRP system. The corresponding results were compared and discussed to validate the model. For the same level of loads, the crack opening can be reduced by 20 to 50% depending on the level of steel ratio.

Belt electrode tetanus muscle stimulation reduces denervation-induced atrophy of rat multiple skeletal muscle groups

Belt electrode-skeletal muscle electrical stimulation (B-SES) involves the use of belt-shaped electrodes to contract multiple muscle groups simultaneously. Twitch contractions have been demonstrated to protect against denervation-induced muscle atrophy in rats, possibly through mitochondrial biosynthesis. This study examined whether inducing tetanus contractions with B-SES suppresses muscle atrophy and identified the underlying molecular mechanisms. We evaluated the effects of acute (60 Hz, 5 min) and chronic (60 Hz, 5 min, every alternate day for one week) B-SES on the tibialis anterior (TA) and gastrocnemius (GAS) muscles in Sprague–Dawley rats using belt electrodes attached to both ankle joints. After acute stimulation, a significant decrease in the glycogen content was observed in the left and right TA and GAS, suggesting that B-SES causes simultaneous contractions in multiple muscle groups. B-SES enhanced p70S6K phosphorylation, an indicator of the mechanistic target of rapamycin complex 1 activity. During chronic stimulations, rats were divided into control (CONT), denervation-induced atrophy (DEN), and DEN + electrically stimulated with B-SES (DEN + ES) groups. After seven days of treatment, the wet weight (n = 8–11 for each group) and muscle fiber cross-sectional area (CSA, n = 6 for each group) of the TA and GAS muscles were reduced in the DEN and DEN + ES groups compared with that in the CON group. The DEN + ES group showed significantly higher muscle weight and CSA than those in the DEN group. Although RNA-seq and pathway analysis suggested that mitochondrial biogenesis is a critical event in this phenomenon, mitochondrial content showed no difference. In contrast, ribosomal RNA 28S and 18S (n = 6) levels in the DEN + ES group were higher than those in the DEN group, even though RNA-seq showed that the ribosome biogenesis pathway was reduced by electrical stimulation. The mRNA levels of the muscle proteolytic molecules atrogin-1 and MuRF1 were significantly higher in DEN than those in CONT. However, they were more suppressed in DEN + ES than those in DEN. In conclusion, tetanic electrical stimulation of both ankles using belt electrodes effectively reduced denervation-induced atrophy in multiple muscle groups. Furthermore, ribosomal biosynthesis plays a vital role in this phenomenon.

Enhancing biological properties with straightforward deposition of durable heparin/chitosan surface coatings on wettable poly(ε-caprolactone)/Tween-20 electrospun fibers

Poly(ε-caprolactone) (PCL) is a hydrophobic aliphatic polyester commonly used as a biomaterial due to its cytocompatibility and biodegradability. However, PCL-based materials are hydrophobic and susceptible to bacterial adhesion and proliferation. To address these disadvantages, this study proposes a direct and practical method for functionalizing the surface and enhancing the biological properties of electrospun PCL fibers using Tween-20 surfactant, followed by the deposition of polyelectrolyte multilayers (PEMs). Tween-20, a neutral and cytocompatible surfactant, was directly incorporated into the fibers without prior surface modifications. The surfactant significantly increased the wettability of the PCL fibers, resulting in water contact angles of 0 degrees, facilitating subsequent functionalization with heparin and chitosan PEMs (with 10, 20, and 30 layers). The materials were characterized through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), water contact angle and mechanical measurements, Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The PEMs remain stable on the fiber surfaces for up to 14 days in a buffer at 37°C. The samples supported high cell viability with no observed cytotoxicity toward human adipose-derived stem cells and no hemolytic activity toward human red blood cells. Antibacterial assays (live/dead and proliferation tests) demonstrated that the coated PCL fibers inhibited the proliferation of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). The PEM coatings significantly enhanced the antimicrobial activity, resulting in a high number of damaged and dead bacterial cells attached to the coated fibers. Therefore, the heparin/chitosan PEMs on Tween-20-modified PCL fibers can prevent bacterial infections while supporting viable mammalian cells.

Preparation of gallic acid-polydimethylsiloxane codeposited carbon fibers to improve interfacial properties of epoxy composites

A novel method, drawing inspiration from the chemistry principle observed in mussels, has been recently developed to augment the wettability and adherence of carbon fibers (CFs) within epoxy resin matrix. This technique entails the concurrent application of gallic acid and aminopropyl double terminated polydimethylsiloxane on CF surfaces via a direct method. Advanced analytical techniques like scanning electron microscopy, X-ray diffraction, infrared and Raman spectroscopy, along with X-ray photoelectron spectroscopy, confirmed the effective simultaneous deposition of these agents, possibly via Michael addition or Schiff base reactions. Incorporation of these treated fibers into epoxy composites resulted in notable performance enhancements. The composites with gallic acid and polydimethylsiloxane modified fibers exhibited up to 14%, 13%, and 27% improvements in interlaminar shear strength, flexural modulus, and flexural strength, respectively, compared to their counterpart with untreated fibers. These results indicate that combining gallic acid and polydimethylsiloxane on CFs is a potent approach to boost the interface qualities of CF-reinforced epoxy resin composites.

Valorization of waste paper sludge as a sustainable source for packaging applications

Paper sludge consists mainly of wet short cellulose fibers that are lost during papermaking and of residual chemicals used in the manufacturing process that remain dissolved in the water. Each ton of paper generates about 40–50 kg of dry sludge, of which 70% is primary sludge. Paper production, which exceeded 400 million tons globally in 2020, generates vast volumes of solid waste. Primary sludge is usually fiber-rich and hence suitable to be recycled back into the papermaking process. However, if the sludge is to be disposed of in landfills, sustainable practices must be developed in order to recover the fibers as they are valuable source for manufacturing high value-added products. This study investigates the valorization of paper sludge discarded by a filter paper manufacturer, with the purpose of producing cellulose acetate films for food packaging. The process involves recovering cellulose fibers from the sludge, purifying them and through acetylation reaction produce cellulose acetate films. FTIR spectra confirmed successful acetylation of fibers and also that acetyl groups reduced the hydrophilicity of cellulose—the contact angle was increased to over 80° from 50° in native cellulose. The films exhibited very good water barrier properties at both 50% and 90% relative humidity (RH).Graphical abstract

АДГЕЗИОННОЕ ВЗАИМОДЕЙСТВИЕ В ГИБРИДНОМ КОМПОЗИТЕ. СВЯЗЬ ЭНЕРГЕТИЧЕСКИХ ХАРАКТЕРИСТИК ФАЗ С ПРОЧНОСТЬЮ

Improvement of stiffness characteristics of polymer composites is conditioned by the development of hybrid composites (containing more than one type of reinforcing continuous fiber) with the provision of effective stress transfer from fibers to binder through the interface. The study of mechanisms of formation of adhesion interaction in hybrid polymer composite consists in purposeful change of energy characteristics of phases in order to achieve the optimal level of adhesion, affecting the strength of composites while providing technological and other factors, predicting their durability. In this work the relationship between the energy characteristics of phases and the strength of hybrid polymer composite was investigated. Microphotographs of wetting of fibers of different nature by liquids were obtained by the optical method, by which the edge angles of wetting were determined, tests were carried out to determine the bending strength of polymer composites. A method for predicting the flexural strength of hybrid polymer composites made by vacuum infusion method has been proposed and experimentally confirmed, which consists in linking the adhesive interaction of components, structural components and flexural strength by determining the change in their energy characteristics of the filler by wetting method.

АДГЕЗИОННОЕ ВЗАИМОДЕЙСТВИЕ В ГИБРИДНОМ КОМПОЗИТЕ. СВЯЗЬ ЭНЕРГЕТИЧЕСКИХ ХАРАКТЕРИСТИК ФАЗ С ПРОЧНОСТЬЮ

Improvement of stiffness characteristics of polymer composites is conditioned by the development of hybrid composites (containing more than one type of reinforcing continuous fiber) with the provision of effective stress transfer from fibers to binder through the interface. The study of mechanisms of formation of adhesion interaction in hybrid polymer composite consists in purposeful change of energy characteristics of phases in order to achieve the optimal level of adhesion, affecting the strength of composites while providing technological and other factors, predicting their durability. In this work the relationship between the energy characteristics of phases and the strength of hybrid polymer composite was investigated. Microphotographs of wetting of fibers of different nature by liquids were obtained by the optical method, by which the edge angles of wetting were determined, tests were carried out to determine the bending strength of polymer composites. A method for predicting the flexural strength of hybrid polymer composites made by vacuum infusion method has been proposed and experimentally confirmed, which consists in linking the adhesive interaction of components, structural components and flexural strength by determining the change in their energy characteristics of the filler by wetting method.

A novel design model for predicting the shear resistance of reinforced concrete beams strengthened with EBR-CFRP systems

Shear resistance prediction of reinforced concrete (RC) beams strengthened with externally bonded reinforcements (EBR) is a challenging task due to the complex nature of shear resisting mechanisms and their intricate interaction. Existing design models often overlook these dependencies, leading to significant variations in prediction accuracy. In this paper, a design model is proposed by integrating the most relevant shear resisting mechanisms based on the evidence demonstrated by a large database of experimental results from RC beams shear strengthened with wet layup carbon fibre reinforced (CFRP) sheets applied according to the EBR technique. The developed approach integrates the simplified modified compression field theory (SMCFT) with a regression-based model. A global sensitivity analysis was conducted according to which closed form equations were derived to obtain the tensile stress factor in cracked concrete and the inclination angle of the critical diagonal crack. A reliability analysis is carried out, and resistance reduction factors are achieved for different levels of reliability index. The database, composed of 284 RC beams shear strengthened with EBR-CFRP technique, is utilized to validate the proposed model, and compare its performance against some well-established existing design models. The results show that the proposed model, with an adequate framework for its use on design practice, outperforms the other considered models.

Efficiency of cotton and fiber wetting in cotton ginning plants

This article provides a comprehensive examination of humidification technologies and points within ginneries, with a specific focus on the moisture content of the produced fiber. Several key aspects are covered, ranging from the assessment of existing humidification technologies to the determination of moisture levels in the fiber across different ginneries. Additionally, the article delves into the changes in moisture content observed in various cotton components during technological processes, particularly in fiber bales utilized in production at the spinning factory "OSBORN TEXTILE," along with associated challenges. By examining these facets, the article provides valuable insights into the intricacies of managing moisture content in cotton processing, from ginneries to spinning factories. The findings contribute to a better understanding of the role of humidification technologies in maintaining optimal conditions for cotton fiber production and subsequent textile manufacturing processes. The identification of challenges and vices allows for targeted improvements and optimizations in the industry's practices.

Dilution-controlled deposition of mixtures of a synthetic polycation and a natural origin polyelectrolyte with anionic surfactants on negatively charged surfaces

The cosmetics industry is constantly seeking sustainable and environmentally friendly ingredients for hair care formulations to replace those traditionally derived from the petrochemical industry. In this context, the substitution of traditional cationic polyelectrolytes, such as poly(diallyldimethylammonium chloride, PDADMAC), by others of natural origin, such as chitosan, is a key challenge to achieve new formulations with a higher degree of naturality and more environmentally friendly without compromising product efficacy. This work investigates the effect of dilution on the phase separation of concentrated binary mixtures of two anionic surfactants (sodium laureth sulfate, SLES, and sodium dodecyl sulfate, SDS) with PDADMAC or chitosan. PDADMAC is a polycation of petrochemical origin, whereas chitosan is obtained from natural resources. Also, how this phase separation affects the formation of conditioning deposits on surfaces that mimic the charge and wettability of damaged hair fibers has been studied. The results show that for polymers of similar molecular weight, the substitution of PDADMAC by a highly charged chitosan is a promising alternative. The deposition is greatly enhanced for model wash formulations containing chitosan after minimal dilution. The results obtained here may pave the way to an important line of research toward improving the sustainability profile of hair care formulations without compromising consumer satisfaction.