Surface Treatment Of Carbon Fibers Research Articles

RETRACTED: Effect of surface treatment of carbon fibers on the mechanical and frictional properties of polyetheretherketone/polytetrafluoroethylene composites: Experimentation and finite element analysis

Polytetrafluoroethylene has many excellent properties and a wide range of applications, but its poor wear resistance, hardness, and creep resistance have severely limited the use of the polytetrafluoroethylene composites. In this work, the surface of carbon fibers was treated with silane coupling agent acetone solution, and then sintering technology was used to prepare carbon fibers/polyetheretherketone (PEEK)/ polytetrafluoroethylene composites. The mechanical and frictional wear properties of the composites were analyzed using an electronic tensile tester, a Shore hardness tester, and a frictional wear tester, and scanning electron microscopy was applied to analyze the surface morphology of the composites after wear. The experimental results shown that the addition of carbon fibers could significantly improve the mechanical properties of the composites, reduce the radial shrinkage, and increase the Shore hardness of the composites. Under the same experimental conditions, the carbon fibers (20 wt.%) /polyetheretherketone/polytetrafluoroethylene composites has the best wear resistance, with a friction coefficient of 0.196 and the wear rate of 2.41 × 10−6 mm3/N·m. In the theoretical simulation, the thermal conductivity of polytetrafluoroethylene composites was predicted using ANSYS software, with the changes in the temperature and friction force in the friction process. The theoretical simulation results matched with the experimental values, which proved the accuracy of the theoretical simulations.

Polyetheretherketone Composites with Appreted Carbon Fibers

The paper investigates the processes of carbon fiber surface treatment and their influence on the properties of polyetheretherketone composites. It has been shown that preliminary thermal activation of carbon fiber followed by treatment with a dressing agent - polyhydroxyether makes it possible to create polyetheretherketone composite carbon-filled materials with an increased level of physical and mechanical properties.

Investigating interfacial adhesion and open-hole compressive (OHC) strength correlations for CFRPs via variations in sizing and oxidative surface treatment

Increasing interfacial shear strength (IFSS) has been observed to improve fracture toughness within carbon fiber/epoxy laminates. However, a direct correlation between IFSS of carbon fiber surface treatments and open-hole compressive (OHC) strength has never been established. Here the effects of systematically altering electrochemical oxidation surface treatments (0, 2 and 3.4 Amps) and sizing deposition levels (Unsized, 1:15 and 1:20 dilution epoxy:water, respectively) to observe the correlation, if any, between microscale IFSS and laminate OHC strength. Increases in OHC strength of up to 30.2% relative to untreated and unsized fibers were observed and attributed to the surface treatments for sized fibers. No changes in OHC strength were observed when the surface treatment was altered for unsized fibers, suggesting a major role of the sizing in governing OHC strength. This is supported by OHC strength increases of up to 49.4% attributed to increased sizing deposition level.

Effect of sizing agent on interfacial properties of carbon fiber-reinforced PMMA composite

The surface treatment of carbon fibers (CFs) was carried out using a self-synthesized sizing agent. The effects of sizing agent on the surface of CFs and the interface properties of CF/polymethyl methacrylate (PMMA) composites were mainly studied. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and static contact angle were used to compare and study the CFs before and after the surface treatment, including surface morphology, surface chemical element composition, and wettability of the surface. The influence of sizing agent on the mechanical properties of CF/PMMA resin composite interface was investigated. The results show that after sizing treatment, the CF surface O/C value increased by 35.1% and the contact angles of CF and resin decreased by 16.2%. The interfacial shear strength and interlayer shear strength increased by 12.6%.

Synthesis of Polyaniline Under Electrolytic Plasma on Carbon Fiber Fabric

AbstractPolyaniline is synthetized on carbon fiber through electrolytic plasma applied in an acid monomer solution, without an oxidant. Pulsed‐plasma carbon fiber surface treatment is performed with two 1.0 kV pulses for 1 µs with an 200 µs off period. Different treatment times and ultrasound presence, to create microbubbles that can help plasma formation, are tested. The ultrasonic bath is not effective to produce higher quantities of polymer. Furthermore, the film formed on the carbon fiber is chemically characterized through treatment in a basic solution followed by immersion in NMP, and through FT‐IR and XPS. The presence of nitrogen in the carbon fiber surface and the characteristic FT‐IR bands of delocalized electrons indicate that the electrolytic plasma treatment is efficient to synthesize polyaniline in its conducting form. Electrochemical activity is accessed by cyclic voltammetry, indicating the formation of electrodes with good reversibility and stability, thereby suitable for supercapacitor applications.

Non-isothermal crystallization behavior of PP/EVA/basalt/carbon fiber composites

The surface treatment of basalt and carbon fiber was carried out by sulfuric acid etching and coupling. Combined fiber was prepared by melt mixing. Polarizing optical microscope (POM) and differential scanning calorimetry (DSC) were employed to investigate the effect of combined fiber on crystallization behavior. To be specific, POM indicated that the addition of combined fiber reduced the crystal size. DSC observations illustrated that the combined fiber accelerated the crystallization rate and increased the crystallization temperature from 112-122 °C to 122-133 °C. It means that combined fiber can make the composites crystallize rapidly at high temperature in production. Modified Avrami models were used to evaluate the influence of combined fiber on the non-isothermal crystallization kinetics of PP. The presence of combined fiber reduced the Avrami exponent (n) from 2.16-3.13 to 1.54-2.49. The results showed that the combined fiber acted as heterogeneous nucleation agent, which changed crystal nucleation mechanism and growth mode.

Effect of moisture content and carbon fiber surface treatments on the interfacial shear strength of a thermoplastic-modified epoxy resin composites

The effect of moisture absorption on the fiber-matrix interfacial shear strength (IFSS) between a polysulfone-modified epoxy matrix and silane surface-treated carbon fiber using a factorial experimental design was studied. Also, two conditions of relative humidity, 25%, and 95%, and likewise six combinations of interfacial adhesion level between the IM7 carbon fiber and the epoxy resin (diglycidyl ether of bisphenol A), modified with polysulfone (PSF) (8.75 wt.%), were studied. The results show that IFSS of the composites increased with both the carbon fiber surface treatments and the epoxy resin modification with PSF. Again, it was found the moisture content had a substantially detrimental effect on the IFSS. However, both the silane treatment and the (PSF) modification of the epoxy resin enhanced the composite's resistance to moisture attack. The ANOVA results showed that the three variables, matrix modification, fiber's surface treatment, and moisture content, were statistically significant. Furthermore, interactions fiber surface treatment–moisture content and fiber surface treatment–epoxy matrix were statistically significant and the interaction between fiber surface treatment and moisture content is as crucial as the polysulfone epoxy modification. It was also found that the silane-treated carbon fibers play a major role in preventing moisture attack to the composite.

Electron microscopy study of surface-treated carbon fiber for interface modification in composites

Relatively poor adhesion of carbon fibers with matrix leads to various serious concerns in high performance composites. Interface debonding during loading is the most vulnerable among them particularly when polymer matrix is used. This paper presents the results of electron microscopy investigation of four different techniques that are beneficial for improving interfacial bonding. These techniques were based on modifying the fiber surface by way of both; coating a film on the fiber and ablating a layer from it. The former employed growth of nanostructures of carbon and zinc oxide by thermal catalytic chemical vapor deposition and magnetron sputtering respectively and depositing a layer of pyrolytic carbon by CVD while the latter involved ablation of an outer layer of fiber using femtosecond laser treatment. Both the approaches relied on introducing mechanical anchoring on the fiber surface by micro roughening anticipating an improved fiber- matrix interfacial bonding. Carbon fiber surface prior and post treatment was investigated microscopically using FESEM and TEM. CNTs growth formed network like structure around the fiber, while PyC coating showed continuous layer around the fiber. HRTEM images of ZnO nanostructures; both nanowires and nanowalls possessed crystalline structure revealed by the presence of Moiré fringes formed due to overlapping of two crystals with different orientation. Laser treated fiber surface showed formation of LIPSS with average periodicity of 147 ± 10 nm.

The effect of sizing and surface oxidation on the surface properties and tensile behaviour of recycled carbon fibre: An end-of-life perspective

Carbon fibre is not widely recycled due to the inconsistent tensile properties of the recycled carbon fibre (rCF). It is unclear whether the surface treatments for virgin carbon fibre (vCF) have an impact on the quality of rCF. This paper presents an experimental investigation into the effect of epoxy sizing and electrochemical oxidation for vCF on the tensile and surface properties of rCF recycled by pyrolysis. Carbon fibre with sizing, or surface oxidation, or both, experience a reduction in tensile strength by 44.6%, 43.7% and 50.1%, respectively, during the recycling process, compared to 19.8% for un-treated fibre. Surface-treated carbon fibres exhibit more surface defects (ID/IG from 1.6 to 2.7 from Raman spectroscopy) and a smaller average crystallite size (from 7.6 nm to 6.2 nm from X-ray diffraction) after recycling. The results indicate that the interactions between the sizing agent and surface functional groups contribute to the down-cycling of carbon fibre.

Comparative Physical–Mechanical Properties Assessment of Tailored Surface-Treated Carbon Fibres

Carbon Fibres (CFs) are widely used in textile-reinforced composites for the construction of lightweight, durable structures. Since their inert surface does not allow effective bonding with the matrix material, the surface treatment of fibres is suggested to improve the adhesion between the two. In the present study, different surface modifications are compared in terms of the mechanical enhancement that they can offer to the fibres. Two main advanced technologies have been investigated; namely, plasma treatment and electrochemical treatment. Specifically, active screen plasma and low-pressure plasma were compared. Regarding the electrochemical modification, electrochemical oxidation and electropolymerisation of monomer solutions of acrylic and methacrylic acids, acrylonitrile and N-vinyl pyrrolidine were tested for HTA-40 CFs. In order to assess the effects of the surface treatments, the morphology, the physicochemical properties, as well as the mechanical integrity of the fibres were investigated. The CF surface and polymeric matrix interphase adhesion in composites were also analysed. The improvement of the carbon fibre’s physical–mechanical properties was evident for the case of the active screen plasma treatment and the electrochemical oxidation.

Molecular Structure Design of Sizing Agent and Its Influence on the Mechanical Properties of CF Reinforced Composite

In this article, phosphate modified epoxy resin (PAEK) and polyethylene oxide (PEO) were used as the main monomers to fabricate a composite sizing agent (TPP) for carbon fiber (CF) surface treatment. The effects of TPP sizing on the surface morphology, activity and wettability of CF were studied by FE-SEM, XPS and contact angle. In addition, friction coefficients, fuzz amount and the mechanical properties of CF filaments, as well as the interlaminar shear strength (ILSS) of CF composites were analyzed. The results indicate that the defects of CF surface were completely repaired by TPP molecules, the content of active groups increased by 24.8 % and the contact angle and the spreading time of EP on CF surface reached respective minimum values of 43.5 ° and 15 s, meanwhile, the friction coefficient and the fuzz amount of the treated CF surface are reduced in the sizing quantity range of 3.0–4.0 mg/g. Thus, there were 36.1 % and 24.3 % enhancement in the breaking strength and elongation of CF filament. In addition, the ILSS of composite prepared with TPP treated CFs was increased from 12.81 to 28.55 MPa.

Examining conductivity, current density, and sizings applied to carbon fibers during manufacture and their effect on fiber-to-matrix adhesion in epoxy polymers

This study provides a comprehensive study of carbon fiber surface treatment conditions for epoxy resins. A set of 27 fibers, derived from DowAska precursor, with alterations to manufacturing conditions only occurring at the electrochemical oxidation and sizing bath. Electrolyte (NH4HCO3) conductivity was varied between 8, 16 and 24 μS/cm while oxidative current density was varied between 0.5, 1.0 and 1.5 A/m2. Subsequent to oxidation, fibers were coated with either epoxy, polyamide or polyurethane compatible sizing. This study is the first to consider electrolyte conductivity, oxidative current density and sizing variables simultaneously and links them to interfacial shear strength (IFSS). Extensive chemical, physical and mechanical characterization was conducted to quantify the changes to fiber properties as a result of treatment variation. Results reveal that varying combinations of electrolyte and applied current density not only vary the degree of oxidation on the fiber, but the types of surface chemistry installed (e.g. ratio of COH, CO, and COOH). Somewhat counter-intuitively, at high conductivities and current densities the degree of oxidized carbon species on the fiber surface is decreased. Indeed, this study shows combinations of surface treatment variables which could be used to promote the formation of surface bound functional groups in preference (e.g. phenolic groups in preference to COOH) to enhance interfacial bonding for a given resin. Determination of fiber roughness for all samples showed no statistical difference between samples, suggesting that mechanical interlocking effects do not play a role in the variations in interfacial adhesion observed herein.

Sizing effects on the interfacial shear strength of a carbon fibre reinforced two-component thermoplastic polymer

Here carbon fibre surface treatment conditions (current, bath conductivity, and sizing) gave a comprehensive set of 27 unique carbon fibre samples. Examination of the interfacial shear strength (IFSS) in a two-component polymethyl methacrylate resin via the V-notch shear test. Epoxy-sized fibres show a strong dependence on surface treatments and were widely variable (25.6 ± 0.72 to 38.5 ± 2.69 MPa). We suggest the epoxy sizing is soluble in the methylmethacrylate monomer and is removed from the surface before complete polymerisation. Adhesion in epoxy-sized fibres seemed linked to the ratio of oxygen and nitrogen on the fibre surface (determined by XPS). Polyamide-sized fibres possessed a smaller data variation (37.3 ± 3.34 to 33.4 ± 3.18 MPa), suggesting the polyamide-sizing masks the underlying surface chemistry of the fibre induced by the variations in surface treatment. A hybrid of these two outcomes was observed with the polyurethane sized fibres (36.1 ± 2.19 to 28.8 ± 2.82 MPa), suggesting a mixture of effects observed above.

Electrochemical Surface Treatment of Discontinuous Carbon Fibers.

We developed an operationally simple electrolytic design for the surface treatment of short carbon fibers. Using X-ray photoelectron spectroscopy (XPS), we demonstrated that the electrochemical surface treatment of discontinuous fibers is highly reproducible, uniform, and tunable. Specifically, total amounts of surface oxygen and nitrogen contents (0 to 17 atomic %) as well as surface oxygen-to-nitrogen ratio (1:0 to 1:2) vary significantly over the ranges of each processing parameter: applied voltage (1.5-21 V), location of carbon fiber (i.e., anode, cathode, or mixed mode), initial temperature (3-70.5 °C), and ammonium bicarbonate concentration (0.005-0.75 M). Optimized processing conditions afforded carbon fibers that have similar surface compositions (86.3 ± 1.1 at. % C, 8.9 ± 0.8 at. % O, 4.7 ± 0.6 at. % N) as those of commercially available continuous fibers. In addition, these fibers retain their mechanical properties (tensile strength and tensile modulus) and exhibit no detectable surface damage based on single fiber tensile tests and scanning electron microscopy (SEM). We also performed a number of control experiments to develop a proposed mechanism for the surface functionalization of the carbon fiber. These mechanistic studies demonstrated that water splitting contributes significantly to the oxidation of carbon fibers and that other species in the chemical equilibria of ammonium bicarbonate (and not just its individual ions) play a significant role in functionalizing carbon fiber surfaces.

Ceramization of Carborane-POSS and Coating on Carbon Fiber via Precursor Infiltration-Pyrolysis (PIP) Method

A novel carborane-POSS pre-polymer has been synthesized and characterized as precursor for ceramic and applied on the surface treatment of carbon fiber by precursor infiltration and pyrolysis (PIP) method. The ceramization transformation process was investigated by using TGA, DSC, Py-GC/MS, etc. Ceramic yield after heating up to 1000 °C in nitrogen was 74.3 % and the produced ceramics exhibit excellent thermal and thermo-oxidative stability. Mechanical measurement revealed that the coated carbon fiber maintained 81.22 % of its original tensile strength, and was stable under high temperature in flowing air up to 600 °C.

Factorial design approach to assess the effect of fiber–matrix adhesion on the IFSS and work of adhesion of carbon fiber/polysulfone-modified epoxy composites

A two-level full factorial design 22 with three replications was employed to assess the effect of the incorporation of PSF into the epoxy matrix and the surface treatment of carbon fibers on the work of adhesion (WA) and the interfacial shear strength (IFSS) of carbon fiber–epoxy composites. The IFSS was determined using the microbond (or microdrop) micromechanical test, and the work of adhesion was estimated using two different procedures: (1) using the Owens and Wendt method, and (2) from the Dupre–Young expression using the contact angle θ of a cured epoxy resin on a single carbon fiber and the surface energy of the cured epoxy resin. It was found that the treatment of the carbon fiber with the silane-coupling agent appreciably increases its polar component because of the nitric acid oxidation and the chemisorption of the silane-coupling agent onto the carbon fiber surface. Also, the O=S=O group present in the polysulfone chain resin fairly increases the polar component of the epoxy–PSF blend. The results show that the wetting of the silane-treated carbon fiber by the thermoplastic-modified epoxy resin is better, thus increasing the fiber–matrix adhesion. It was also found that there is a similarity between the trends of both, the IFSS and the WA results. Also, from the ANOVA results it was also seen that both the incorporation of the PSF to the epoxy matrix and the surface treatment of the carbon fibers and their interaction were statistically significant to the IFSS and the WA.

(Invited) Aqueous Amination of Carbon Fiber Surfaces for Improved Composite Properties

Meeting the global requirements for reduced CO2 emission and increased vehicle fuel economy requires new technology development within the transportation industry. Vehicle lightweighting is a particularly important approach because reducing primary vehicle weight can often enable secondary mass reductions. Broad adoption of composite materials in the automotive industry requires composite development – including resin, fiber, and fiber interphase – and the ability to manufacture components at relevant rates and costs. As part of a broad effort to develop low-cost carbon fiber-reinforced composites, research at Dow has demonstrated a low-cost aqueous route to electrochemically modify fiber surfaces with amine-based reactive molecules. These functionalized fibers can then provide advantages in material handling and interphase development that enable lower-cost lightweighting solutions. While electrochemical surface treatment of carbon fibers is a mature field, this presentation will provide a demonstrative example of an early stage industrial approach to using electrochemical methods, from small scale concept screening to early-pilot scale material testing.

A two-step carbon fiber surface treatment and its effect on the interfacial properties of CF/EP composites: The electrochemical oxidation followed by grafting of silane coupling agent

A two-step surface treatment was applied on the surfaces of polyacrylonitrile(PAN)-based carbon fibers (CFs) including the electrochemical oxidation process followed by grafting of silane coupling agent KH550. The evolution of the physiochemical structure of the fiber surface during the surface treatment was investigated using Infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and surface tension/dynamic contact angle measurements. The results showed that the CF surface exhibited a significant increase in the relative content of oxygen-containing functional groups after surface treatment while its crystal structure had little change after the grafting of KH550 agents. Effects of surface treatment on the mechanical properties of CFs and the interfacial properties, including the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy (CF/EP) composites were evaluated in detail. Both the electrochemical oxidation and the introduction of KH550 agents onto CF surfaces improved the IFSS and ILSS values of CF/EP composites by comparison with untreated fibers. In particular, the maximum interfacial properties of CF/EP composites were obtained by the electrochemical oxidation together with the grafting of KH550 agents onto CF surfaces.

Surface Treatment of Carbon Fibers by Oxy-Fluorination

In this paper, the oxy-fluorination process and the influence of different concentrations of fluorine and oxygen in the gas phase on the physicochemical properties of polyacrylonitrile(PAN)-based carbon fibers are described. The properties of the treated carbon structures are determined by zeta potential and tensiometry measurements. In addition, changes in surface composition and morphology are investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Adhesion properties are characterized by the single fiber pull-out (SFPO) test. Furthermore, changes in intrinsic properties are described by means of tensile and density measurements. After a primary desizing effect by oxy-fluorination, an increased number of oxygen-containing surface functional groups could be detected, which led to more debonding work in SFPOs with an epoxy-based matrix. It was also shown that the polar surface energy grows with rising fluorine concentration in the reaction gas mixture. In addition, a minor increase of ~10% in the maximum strength of PAN-based carbon fibers is detected by single fiber tensile measurements after oxy-fluorination with a fluorine content of 5% in the reaction mixture.

Thermal and mechanical properties of C/SiC composites fabricated by liquid silicon infiltration with nitric acid surface-treated carbon fibers

Thermal and mechanical properties of C/SiC composites fabricated by liquid silicon infiltration with nitric acid surface-treated carbon fibers