Fiber Surface Wettability Research Articles

Surface modification of carbon fibres via plasma-activated water for mitigating burnout risk from direct plasma treatment

This study presents a novel plasma jet discharge device designed to indirectly treat carbon fibre materials with plasma-activated water. This innovative method effectively mitigates issues related to carbon fibre conduction and combustion, which are common challenges encountered when directly modifying fibres using a plasma jet. Specifically, the atmospheric composition is adjusted to modulate the active particles in the liquid phase. The experimental results demonstrate that this technique significantly increases the surface wettability of carbon fibres without damaging their structure. Under the conditions of argon/oxygen cascade discharge, oxygen-containing substances generate ionomers that activate the water, which in turn introduces oxygen-containing groups (e.g., C−O, C=O, O−C=O) onto the carbon fibre surface. These groups catalyse monomer polymerisation on the material surface, which increases the wettability of the carbon fibres, as evidenced by a significant reduction in the water contact angle from 80.12° to 55.31°. This in turn improves the bonding strength with epoxy resin and slightly increases the monofilament strength. Furthermore, composites produced by this method exhibit 21% higher interlaminar shear strength than the untreated sample and an increased O/C ratio of up to 24.55%. In summary, these findings provide a valuable theoretical basis for enhancing the surface properties of carbon fibre composites through plasma–liquid interactions and open new possibilities for high-performance carbon fibre–resin matrix composites.

A sulfonated hyperbranched bio-based waterborne polyurethane sizing coating for the enhancement of mechanical properties and surface wettability of carbon fibres

Wet-weaving and cluster braiding in industrial production processes generate irreversible defects and grooves in carbon fibre (CF) filaments, which reduce the service life and mechanical properties of the fibres. Additionally, the fibre surface covered with numerous inactive carbon-containing groups and presents chemical inertness, which limits the prospects of CF applications. Hence, the hyperbranched bio-based waterborne polyurethanes (SWPU) possessing the synergism of sulfamate and carboxylate complex hydrophilic units were adopted as sizing coatings to improve the flexural and tensile strengths of CF, as well as fibre surface roughness and wettability. The SWPU is designed on dihydroxymethylbutyric acid and sulfamates (A95) as per- and post-chain extenders, respectively, trimethylolpropane (TMP) as an intramolecular cross-linker, and plant-extracts castor oil (CO) replacing petroleum-based petrochemicals as the soft-segments. The construction of CO-TMP hyperbranched cross-linking networks and the strengthened hydrogen-bonding effects of the polar sulfamates positively affect the intermolecular interactions and configuration stability of SWPU sizing coatings. SWPU revealed favourable thermo-mechanical properties achieving a T5% decomposition temperature and toughness of 297.83 °C and 35.24 MJ/m3. The coating effects of the bio-based sizing agents not only repaired defects and improved surface roughness on CF, but the polar groups in SWPU comprising SO3Na, carbamate and polyurea promoted the chemotactic activity and wettability of the fibres. The surface energy and tensile strength of the SWPU sized CF reached 43.75 mN/m and 5.68 GPa, respectively, which were 45.4 % and 30.7 % higher compared to original CF. The research contributes to the development and industrial production of high-performance, eco-friendly bio-based sizing coatings.

Numerical investigation of mesoscale multiphase mass transport mechanism in fibrous porous media

At present, the proton exchange membrane fuel cell (PEMFC) is one of the most promising new energy solutions. The structure and material properties of the gas diffusion layer (GDL) are important factors that restrict the efficient water management and structural stability of PEMFCs. The complex mesoscopic fibrous porous structure of the GDL results in complex multiphase flow dynamics problems that have highly nonlinear characteristics. It is difficult to describe the details of mesoscopic multiphase coupled transport dynamics and numerically solve problems in which there is a two-phase flow with a high-density ratio. To solve these problems, a mesoscopic multiphase coupled transport model based on a lattice Boltzmann method and volume-of-fluid (LBM-VOF) model is proposed. Moreover, we also discuss the mechanism of the interaction between the fibrous porous structure and internal multiphase flow. The results obtained illustrate that the proposed method can obtain dynamic details of the flow field for fibrous porous media. The surface wettability of fibres strongly influences both the distribution and stability of liquid water clusters within porous materials. Concurrently, the fibre diameter assumes a pivotal role in governing lateral water diffusion and exclusion efficiency. This work lays a foundation for efficient water and thermal management of PEMFCs.

Aging effect on surface chemistry and sorption properties of atmospheric pressure plasma treated lignocellulosic jute fibers

Jute fibers are characterized by a heterogeneous chemical composition (cellulose and non-cellulosic components) and a complex layered structure with a hydrophobic surface outer layer responsible for their low wettability. In this work, after the removal of water-soluble components, raw jute fibers were subjected to atmospheric pressure dielectric barrier discharge (DBD) under different conditions (at 150 or 300 Hz) to tailor jute fiber surface structure and wettability. The research was focused on the aging effect during natural aging in a standard atmosphere investigated up to three weeks after DBD treatment. Alterations in the surface morphology of DBD-treated jute fibers were investigated by FE-SEM and AFM, while ATR-FTIR, XPS, and electrokinetic measurements were used to assess the changes in the jute fiber surface chemistry. Sorption properties were monitored through wetting time and capillary rise measurements. The sorption properties of DBD-treated jute fibers were improved (about 100 times lower wetting time and 15 % higher capillary rise height in comparison to untreated) due to the changes in surface chemistry (decreased lignin and hemicellulose content in parallel with cellulose oxidation) and morphology (about 4.6 times higher average roughness). The electrokinetic and sorption properties measurement confirmed the significance of aging effects in lignocellulosic fibers' functionalization using plasma.

Fully bio‐based thermoset composites from UV curable prepregs: Vegetable oil acrylate impregnated hemp nanopaper

AbstractModern thermoset composite matrices are primarily prepared from petroleum‐based plastics, while reinforcements commonly consist of non‐renewable and energy‐demanding glass and carbon fibers. Herein, a non‐chemically treated hemp fiber‐reinforced composite was prepared from bio‐based components: hemp nanopaper (NP) and acrylated epoxidized soybean oil (AESO) or acrylated rapeseed oil (ARO). A commercial‐grade AESO was selected as a reference and compared to ARO prepared in a one‐step synthesis. The impregnation process was examined in detail by studying the impact of surface wetting, temperature, and vacuum on the composite structure. ARO has excellent fiber surface wettability, showing initial contact angles between 46.5° and 48.2° on hemp NP. A more than 10‐fold difference in viscosity between AESO and ARO was observed. ARO composite with 50 wt% hemp loading achieved a Young's modulus of 1.3 GPa, a tensile strength of 26 MPa, and a storage modulus of 4.4 GPa (at 20°C). The results are supplemented by scanning electron microscope analysis of composite morphology via liquid nitrogen fracture and tensile failure analysis, that is, fractography. Dielectric spectroscopy analysis shows that composites have the potential to replace epoxy/paper composite insulators.

Improving Fiber-Matrix Compatibility by Surface Modification of Coconut Coir Fiber Using White Rot Fungi

Compatibility between elements in natural fiber based-composite always becomes a hot issue. The presence of lignin in natural fibers inhibits interlock with its matrix. This research investigates the degradation of lignin encapsulating coconut coir fiber using white-rot fungus (Pleurotus Ostreatus) and its effect on composite compatibility. The process of delignification was carried out by exposing coconut coir fibers in the media where the white-rot fungus was incubated and grown. The period of exposure was 10, 20, and 30 days, and the ratio of coconut coir fiber to white-rot fungi were 1:1, 1:1.5, and 1.5:1 (by weight). To find the effect of delignification, several tests were conducted namely lignin content, fiber surface morphology, wettability, and pull-out tensile test. The results show that there is a reduction in the lignin content of the fibers. The largest reduction is 27.11% for 30 days of exposure times with the ratio of 1:1.5. The surface morphology of the fibers is smoother due to the loss of lignin. In the wettability test, it is found a decrease in the contact angle between the fibers and the resin. In line with that, the pull-out tensile test reveals a double increase in the IFSS value reaching 115.54%. This significant improvement might be due to the interlocking ability contributed by surface modification of the fibers. Since this chemical-free treatment promotes good composite compatibility, it might be introduced as an environmentally friendly treatment in the production of natural fiber based-composites

Latent active unit triggered crosslinking inside aramid fiber with improved transverse connection and composite properties

Weak transverse connection inside organic fiber limited its structural stability during processing and mechanical property in composite products. In this article, we utilized the latent activity of imidazole unit of aramid fiber, proved its spontaneous feasibility in open-ring reaction with epoxy-contained compound as anionic polymerization under suitable high temperature using in-situ Fourier Transform Infrared Spectroscopy (in-situ FTIR). Utilizing this in-situ polymerization inside fiber, crosslinked fiber linked between imidazole spots was obtained via simple penetrating bifunctional 1,3-Bis(Oxiran-2-Ylmethoxy)Benzene (RDGE) inside aramid fiber and heat annealing. Crosslinked fiber showed stable excellent mechanical strength, while the composite interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) respectively improved by 31.49% and 28.20% due to the suppressed axial peeling due to crosslinking enhanced transverse connection, and improved fiber surface wettability without any further surface modification. Besides, compressive strength of modified fiber reinforced composite also improved by 59.84%, while according to the digital images revealed the interfacial failure dominated compressive failure focused in the destroyed area, it was further founded that composite of aramid fiber with much lower bending stiffness than carbon fiber performed highly sensitive dependence with composite interfacial combination.

Fabrication of cellulose acetate/gelatin-eugenol core–shell structured nanofiber films for active packaging materials

In this study, novel active materials based on cellulose acetate (CA) and gelatin (Gel) for the release of eugenol (Eg) were developed by fabricating CA/Gel-Eg core–shell structured nanofiber films using the coaxial electrospinning technique. These electrospun nanofibers were coated with a CA shell, which has excellent water stability. Eg was encapsulated on the core part of the Gel. CA/Gel-Eg fiber morphology, structure, thermal, surface wettability, mechanical, encapsulation efficiency, release profile, and biological activity were evaluated. Results showed that the Eg-loaded nanofibers had uniform fiber morphologies and average fiber diameters ranging from 302.5 to 166.6 nm. Eg could be efficiently encapsulated in nanofibers and released for 120 h. Additionally, the CA/Gel-Eg core–shell structured nanofiber films displayed good Eg dose-dependent antibacterial activity. These findings could lead to a new strategy for developing electrospun fibers with a core–shell structure for active food packaging applications.

Liquid Repellence of Phobic Fiber Networks.

The wetting behavior of fiber networks, which are central to many research and industrial applications, can be difficult to predict accurately owing to their complex, heterogeneous structure. The cylindrical pore model, widely used to interpret and predict the forced wetting of hydrophobic porous materials, often does not yield correct results when working with fibrous networks like paper substrates and non-woven fabrics. This is because these materials exhibit variation in pore size, fiber length, and fiber diameter, as well as a reentrant pore geometry. Quantitative prediction of the critical wetting resistance of hydrophobized papers to arbitrary entrant liquids requires a more sophisticated analytical approach that considers this unique fibrous structure and the effect of stochastic variations within the pore matrix. In this work, we directly measure the critical breakthrough pressure for different porous substrates across various wetting entrant liquids. To isolate the effects of the structure and stochastics on critical wetting behavior of fibrous networks, we analyze additional materials strategically chosen for their subsets of structural features. Ultimately, we formulate a method that demonstrates physical reasonableness, numerical accuracy, and the ability to elucidate the effects of pore size, pore size distribution, fiber diameter, fiber diameter distribution, surface wettability, and liquid surface tension on critical breakthrough pressure of liquids through hydrophobic fibrous networks.

Enhanced interfacial properties of hierarchical MXene/CF composites via low content electrophoretic deposition

The weak fiber-matrix interface is a bottleneck hindering the development of carbon fiber composites . In this work, an optimized electrophoretic deposition (EPD) approach was explored to improve the interfacial properties by depositing uniformly two-dimensional MXene (Ti 3 C 2 T x ) nanoparticles onto the surface of carbon fibers (CF). The MXene-CF hybrids were then used to fabricate continuous carbon fiber reinforced polymer (CFRP) composites. The results manifested that the presence of MXene nanoparticles on the CF surfaces could significantly increase the fiber surface energy and wettability , as well as their surface roughness. As a result, a remarkable increase of the interfacial strength and flexural properties of CFRP has been observed. The functionalized MXene–CF–epoxy composites witnessed a prominent enhancement of interlaminar shear strength (ILSS), flexural strength and monofilament tensile strength compared to their unfunctionalized counterparts. The versatile EPD strategy proposed herein, constitutes a promising approach for CFRP modification that can lead to significantly improved performance. • A homogeneous MXene attachment to the CF surface was achieved via a novel EPD process. • The EPD technique was optimized to prevent oxidation and agglomeration of MXene nanoparticles. • Enhancements of 75%, 50.4%, and 32.7% in ILSS, flexural strength, and single fiber tensile strength were obtained. • The interfacial strengthening mechanism was ascribed to mechanical interlocking, local stiffening, and hydrogen bonding.

Reinforcement of nest‐like Zn layers on the surface of carbon fibers for rigid polyurethane composites

AbstractIn this paper, the nest‐like Zn layers on the surface of short carbon fibers (CFs) was obtained by electrodeposition technique to improve the mechanical properties of rigid polyurethane (RPU) composites. The scanning electron microscopy (SEM) showed that the desired nest‐like Zn crystals were successfully deposited on the surface of CFs. The X‐ray powder diffractometer (XRD) and contact angle instrument were used to analyze the crystal composition of the layers and the wettability of fiber surface. Compared with pristine short carbon fibers/rigid polyurethane (CFs‐RPU) composites, the tensile strength, bending strength, impact strength and interlaminar shear strength (ILSS) of nest‐like Zn layers decorated short carbon fibers/rigid polyurethane (NS‐CFs/RPU) composites were improved simultaneously. Dynamic mechanical test (DMA) results showed that the nest‐like Zn layers on the surface of CFs effectively improved the interfacial bonding strength between CFs and the RPU matrix. In addition, the cross‐section of NS‐CFs/RPU composites showed the metal layer combines well with the matrix. The above results indicated that the improvement of strength and toughness of NS‐CFs/RPU composites was attributed to the pinning effect of the nest‐like Zn layers on the surface of carbon fiber and the increased of crack propagation path.

Improved the surface properties of carbon fiber through hyperbranched polyaryletherketone sizing

AbstractA heat‐resistant soluble hyperbranched polyaryl ether ketone (HPAEK) is synthesized as the main resin of sizing agent and coated on the surface of carbon fiber (CF) with active group. As a result, the monofilament tensile strength of CF is increased by 12.00% and due to the improved fiber surface wettability and interface compatibility between CF and polyether ether ketone (PEEK), a 68.29% increase of interlaminar shear strength is achieved.

MXene modified carbon fiber composites with improved mechanical properties based on electrophoretic deposition

To improve the weak fiber-matrix interface of carbon fiber composites, two-dimensional transition metal carbides or nitrides of MXene (Ti3C2Tx) nanosheets were introduced onto the surfaces of carbon fiber (CF) through electrophoretic deposition (EPD) technology for the first time. The MXene deposited CF was further infiltrated with epoxy resin by vacuum-assisted resin infusion (VARI) to fabricate CFRP composites. Results indicated that the MXene nanoparticles deposited on the surfaces of CF could significantly enhance fiber surface energy and wettability as well as surface roughness, which in turn remarkably increased the interfacial strength and flexural properties of fiber-resin. The MXene/oxidised CF/epoxy composites showed a 53% improvement in interlaminar shear strength (ILSS), a 22.2% enhancement in flexuous strength, and a 29.2% increment in monofilament tensile strength than non-functionalised specimens. This simple and effective strategy provided a promising approach for effective CFRP modification and continuous industrial production.

Improving the Interfacial Adhesion of Carbon Fiber/Polyether Ether Ketone Composites by Polyimide Coating

AbstractPolyimide (PI) as a sizing agent for short carbon fiber (SCF) was explored, and a series of SCF‐reinforced polyether ether ketone (PEEK) composites with PI sizing concentrations varying from 0 to 2.0 wt % were fabricated using the extrusion and injection molding techniques. It was found that the PI sizing layer forms homogeneously and compact on the SCF surfaces, and when the PI sizing concentrations was 1.0 wt %, the tensile strength and flexural strength of the corresponding SCF/PEEK composite was significantly increased by 16.8 % and 8.2 % respectively in comparison with the untrelated case. Additionally, dynamic mechanical analysis (DMA) curves demonstrated that storage modulus of SCF/PEEK composites were enhanced with the increasing concentration of PI sizing, resulting the higher stiffness and the lower damping behavior of the composites. Further, the single fiber pull‐out testing was also measured, with the increased interfacial shear strength (IFSS) of CF/PEEK composites by 24.8 % from 70.6 to 88.1 MPa for the CF modified with 1.0 wt % PI sizing, which illustrated that PI sizing can improve fiber surface wettability and interfacial adhesion between CF and PEEK.

Surface wettability aging behavior of aramid fiber III after oxygen plasma treatment

Aramid Fiber III was modified by oxygen plasma treatment. The fiber surface wettability before and after different oxygen plasma treatment pressure, and surface wettability aging behavior were observed by Dynamic Contact Angles Analysis (DCAA), respectively. The results showed that aramid fiber surface wettability were increased after oxygen plasma treatment. The total surface free energy increased from 37.78 mJ/m2 for untreated sample to 69.63 mJ/m2 with 40 Pa plasma treated fiber. The fiber surface wettability decreased slowly with storage time in air. The fiber surface wettability decreased from 67.79 mJ/m2 for 20 Pa plasma-treated sample to 63.85 mJ/m2 after 30 days.

Effect of fiber surface modifications on the coalescence performance of polybutylene terephthalate filter media applied for the water removal from the diesel fuel

In this work the coalescence performance of the melt-blown structures applied for removal of emulsified water from the diesel fuel is studied. Fibrous polyester media (polybutylene terephthalate, PBT) were fabricated in-house using the melt-blow technique. Postproduction treatment towards the fiber modification involving hydrolysis of the surface with sodium hydroxide or exposure to a low temperature plasma was applied. Different properties of polymer surface were obtained for each modification method, which was verified by the capillary rise test with oil and water. The applied treatment had a significant impact on the coalescence performance comparing to the unmodified PBT structure. In contrary to numerous experimental studies the hydrophilic polyester media obtained by hydrolysis performed much worse than plasma treated filters. It was also shown that the combination of water wettable and non-wettable fibers respectively on the inlet and outlet can significantly improve the separation efficiency. However, in such case the pressure drop is significantly increased as the water captured and collected within the inlet layer is not effectively transported to the outlet. This confirmed that the wettability of fiber surface is not an independent parameter which affects the process. The filter material should be carefully selected with regards to both structural and surface properties of adjacent layers to form a reasonable saturation of the coalescence layer for the high efficiency and also enable the transport of collected liquid to the outlet. Both the structural and surface properties have a pronounced impact on the coalescence efficiency and detachment of droplets from the porous structure on the outlet.

Facile Strategy of Improving Interfacial Strength of Silicone Resin Composites Through Self-Polymerized Polydopamine Followed via the Sol-Gel Growing of Silica Nanoparticles onto Carbon Fiber.

In the present research, to enhance interfacial wettability and adhesion between carbon fibers (CFs) and matrix resin, hydrophilic silica nanoparticles (SiO2) were utilized to graft the surface of CFs. Polydopamine (PDA) as a “bio-glue” was architecturally built between SiO2 and CFs to obtain a strong adhesion strength and homogenous SiO2 distribution onto the surface of CFs. The facile modification strategy was designed by self-polymerization of dopamine followed by the hydrolysis of tetraethoxysilane (TEOS) onto carbon fibers. Surface microstructures and interfacial properties of CFs, before and after modification, were systematically investigated. The tight and homogeneous coverage of SiO2 layers onto the CF surface, with the assistance of a PDA layer by self-polymerization of dopamine, significantly enhanced fiber surface roughness and wettability, resulting in an obvious improvement of mechanical interlocking and interfacial interactions between CFs and matrix resin. The interlaminar shear strength (ILSS) and the interfacial shear strength (IFSS) of CF/PDA/SiO2 reinforced composites exhibited 57.28% and 41.84% enhancements compared with those of untreated composites. In addition, impact strength and the hydrothermal aging resistance of the resulting composites showed great improvements after modification. The possible reinforcing mechanisms during the modification process have been discussed. This novel strategy of developed SiO2-modified CFs has interesting potential for interfacial improvements for advanced polymer composites.

Non-woven composites intensification properties for air filters by plasma pre-treatment

The nonwovens use in the automotive industry has increased significantly. Nonwovens for air filters can be changed in a desired direction to have specific properties. The use of non-woven textiles in the automotive industry has the following advantages: it reduces the weight of the vehicle, increases comfort and provides improved insulation, fire retardancy and resistance to water, fuels, extreme temperatures and abrasion. The electrospinning process is one of the nanofibres, two-layer and multilayer composites with their participation obtaining methods. The low frequency plasma surface modification of needle-punched polyethilenthereftalat (PET) nonwoven fibres is good possibility to intensification the process and the rate of increase of the mass of nanolayer regarding to its’ hydrophobicity. The plasma physicochemical treatment type allows adhesion change and change of electro physical properties at the expense of new active centres formation that do not exist in the native fibre. In this study, different gases (Ar, O2 and air) and electrical conditions were employed. The surface changes of PET fibres were investigated by cation exchange capacity (CEC) determination and its influence on the mass nanofibres increase rate. Observation revealed the plasma treatment significantly change surface wettability of PET fibres. The effect of caused change on the electrospinning process is analysed.

Sodium bicarbonate treatment of coir fiber on wettability and shear strength of coir fiber-epoxy composite

This research presented the influence of treated coir fiber with sodium bicarbonate on wettability and interfacial shear strength (IFSS) of coir fiber-epoxy composite. Coir fibers were immersed in the solution of sodium bicarbonate with three different densities (8wt%, 10wt%, and 12wt %) for 24 hours and 120 hours. Epoxy resin was utilized as a matrix of composite. Wettability and IFSS of coir fiber-matrix adhesion were evaluated. Fiber wettability to the matrix was performed by measuring the droplet contact angle. In addition, the IFSS of coir fiber - epoxy matrix was investigated by pull out method. The surface morphology of interfacial bonding between fiber and matrix after pull out testing was evaluated by scanning electron microscopy (SEM). The results show that fiber surface wettability was influenced by sodium bicarbonate where the contact angle decrease after treatment. It suggests that good wetting of fiber and matrix. While the density of 12 wt% sodium bicarbonate for 120 hours possessed the highest interfacial shear strength of fiber-epoxy adhesion compared with other densities.

Grafting of active carbon nanotubes onto carbon fiber using one-pot aryl diazonium reaction for superior interfacial strength in silicone resin composites

Abstract A novel and effective method was proposed for grafting carbon nanotubes (CNTs) with amino groups onto the surface of carbon fibers (CFs) by using one-pot aryl diazonium reaction in mild, eco-friendly conditions. Based on the diazonium reaction, CNTs were grafted with phenyl amino groups, and then functionalized CNTs (CNT-NH2 ) were modified onto the fiber surface to enhance fiber surface roughness and wettability , which could potentially increase interfacial strength of composites. Homogeneous multi-scale structures with different concentrations of CNTs were achieved. Interfacial properties of hybrid composites were closely dependent on the grafting density. The resulting hierarchical reinforcements improved composites interfacial strength significantly by the enhanced mechanical interlocking and the formed chemical bonding at the interface.