Influence of oxygen plasma treatment parameters on the properties of carbon fiber

This study is focused on the impact of oxygen plasma treatment on properties of carbon fibers and interfacial adhesion behavior between the carbon fibers and epoxy resin. The influences of the main parameters of plasma treatment process, including duration, power, and flow rate of oxygen gas were studied in detail using interlaminar shear strength (ILSS) of carbon fiber composites. The ILSS of composites made of carbon fibers treated by oxygen plasma for 1 min, at power of 125 W, and oxygen flow rate of 100 sccm presented a maximum increase of 28% compared to composites made of untreated carbon fibers. Furthermore, carbon fibers were characterized by scanning electron microscopy (SEM), tensile strength test, attenuated total reflectance Fourier transform infrared (ATR-FTIR), and Raman spectroscopy analyses. It was found that the concentration of reactive functional groups on the fiber surface was increased after the plasma modification, as well the surface roughness, which finally improved the interfacial adhesion between carbon fibers and epoxy resin. However, high power and long exposure times could partly damage the surface of carbon fibers and decrease the tensile strength of filaments and ILSS of treated fiber composites.     

Mechanical properties of carbon fiber composites modified with nano-SiO2 in the interphase

The performance of carbon fibers-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fibers/epoxy composites, nano-SiO₂ particles were introduced to the surface of carbon fibers by sizing treatment. Atomic force microscope (AFM) results showed that nano-SiO₂ particles had been introduced on the surface of carbon fibers and increase the surface roughness of carbon fibers. X-ray photoelectron spectroscopy (XPS) showed that nano-SiO₂ particles increased the content of oxygen-containing groups on carbon fibers surface. Single fiber pull-out test (IFSS) and short-beam bending test (ILSS) results showed that the IFSS and ILSS of carbon fibers/epoxy composites could obtain 30.8 and 10.6% improvement compared with the composites without nano-SiO₂, respectively, when the nano-SiO₂ content was 1 wt % in sizing agents. Impact test of carbon fibers/epoxy composites treated by nano-SiO₂ containing sizing showed higher absorption energy than that of carbon fibers/epoxy composites treated by sizing agent without nano-SiO₂. Scanning electron microscopy (SEM) of impact fracture surface showed that the interfacial adhesion between fibers and matrix was improved after nano-SiO₂-modified sizing treatment. Dynamic mechanical thermal analysis (DMTA) showed that the introduction of nano-SiO₂ to carbon fibers surface effectively improved the storage modulus of carbon fibers/epoxy.     

Jute fabric reinforced engineering thermoplastic sandwich composites. I. The effect of molding time

Jute fabric‐reinforced sandwich composites were fabricated using engineering thermoplastics. The jute fabrics were precoated with thermosetting resin to improve their thermal resistance before molding of the composites. Thermal gravimetric analysis (TGA) studies revealed that the resin coated fabrics decomposed at higher temperature than the uncoated jute. The onset of degradation of the coated fibers also falls between that of jute fibers and the thermoset resins. This indicates the presence of good interfacial bonding between jute fibers and both resins. Isothermal TGA studies revealed that jute could withstand brief exposure to higher temperature at 270 and 290°C. The sandwich composites were fabricated at 270°C by compression molding for 1.5 and 3 min in each case, and then characterized by flexural, tensile and morphological studies, i.e., SEM and optical microscopy. The uncoated jute fabric yielded composites of superior mechanical properties even with 3 mins molding at 270°C which is close to the degradation temperature of uncoated jute fibers. This is an indication that it is feasible to prepare jute fiber filled engineering polymer composites provided the exposure time at high temperature during processing does not exceed 3 mins as determined by TGA isothermal studies. SEM studies revealed strong fiber/matrix interfacial bonding between jute and the thermoset resins while the inferior mechanical properties of the resin coated sandwich composites could be attributed to the poor interfacial bonding between the already cured thermoset coating and the matrix based on optical microscopy of the polished cross‐sections. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of multi‐walled nanotubes on the interlaminar shear strength of glass fiber/acrylate composite fabricated by stepwise ultra‐violet light curing

The interlaminar shear strength (ILSS) of glass fiber/acrylate composite with stepwise ultraviolet (UV) light curing was enhanced by adding multi‐walled carbon nanotubes (MWCNTs) into the resin matrix. The maximum content of MWCNTs that can be used in the process was investigated. Differential scanning calorimetry (DSC) results indicated that prepreg with MWCNTs of more than 0.5% by weight was difficult to cure by UV light because of its poor UV light penetration ability. The ILSS was improved obviously due to the improved resin toughness, crack propagation resistance and interfacial adhesion between the resin and glass fibers according to SEM images. Experimental results suggested that the addition of MWCNTs is an effective method to improve the ILSS of UV stepwise curing composites. POLYM. COMPOS., 38:2113–2118, 2017. © 2015 Society of Plastics Engineers     

Temperature effect on interfacial bonding property of single‐carbon fiber/epoxy resin composite

The changes in interfacial fracture energy of three kinds of commercially sized carbon fiber (CF)/epoxy resin composites in the range from ambient temperature to 130°C were investigated using the single‐fiber fragmentation test to evaluate the heat resistance of the interphase. The effects of CF sizing on the interfacial bonding property were studied using desized CF/epoxy resin composites. Thermogravimetric analysis and differential scanning calorimetry of the combination of sizing and matrix were employed to investigate the role of sizing on the variations in the fiber/matrix interfacial property under elevated temperature. The interfacial fracture energy values of all the studied CF composites were found to decrease quickly during the initial stage of temperature rise and drop gradually at higher temperature. At elevated temperature, the desized CF composites had higher heat resistance than the corresponding sized fiber composites. The differences in the interfacial heat resistance among the three kinds of CF composites and the difference in the interfacial thermal stability between the sized and the desized fiber composites were related to different glass transition temperatures of the interphases. The interaction between sizing and the matrix and the chain motion of the crosslink structure of the interphase has been suggested to determine the interfacial heat resistance. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Improvement of Interfacial Adhesion of Glass Fiber/Epoxy Composite by Using Plasma Polymerized Glass Fibers

This study intends to produce plasma polymer thin films of γ-glycidoxypropyltrimethoxysilane (γ-GPS) on glass fibers in order to improve interfacial adhesion of glass fiber-reinforced epoxy composites. A low frequency (LF) plasma generator was used for the plasma polymerization of γ-GPS on the surface of glass fibers at different plasma powers and exposure times. X-ray photoelectron spectroscopy (XPS) and SEM analyses of plasma polymerized glass fibers were conducted to obtain some information about surface properties of glass fibers. Interlaminar shear strength (ILSS) values and interfacial shear strength (IFSS) of composites reinforced with plasma polymerized glass fiber were evaluated. The ILSS and IFSS values of non-plasma polymerized glass fiber-reinforced epoxy composite were increased 110 and 53%, respectively, after plasma polymerization of γ-GPS at a plasma power of 60 W for 30 min. The improvement of interfacial adhesion was also confirmed by SEM observations of fractured surface of the composites.     

Optimal performances of ultrasound treated kenaf fiber reinforced recycled polypropylene composites as demonstrated by response surface method

Kenaf fiber (KF) reinforced recycled polypropylene (RPP) composites were produced by melt cast method. To improve interfacial adhesion between fiber and RPP matrix, fiber surface modification was carried out by means of ultrasound treatment. Maleic anhydride grafted polypropylene (MAPP) was used as a coupling agent. Composites were examined by mechanical test, melt flow indexing test, scanning electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Water uptake analysis and accelerated weathering test were carried out to find the suitability of the composites in outdoor application. Among the raw fiber contents ranging 10?50 wt % in the composites, the maximum tensile strength (TS) was observed at 40 wt % KF loading without using MAPP. Treated KF‐based composite with MAPP promotes this maximum TS value, which is 57% higher than that of raw KF‐based composite. TGA and DSC analyses exhibit an enhancement of thermal stability in treated KF‐reinforced RPP composites with MAPP. Incorporation of MAPP in the composites shows higher activation energy, suggesting improved interfacial bonding between fibers and matrix. Response surface method was employed to demonstrate the optimal treatment parameters for TS, showing excellent agreement with the observed values. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Application of sustainable treatments to fiber surface for performance improvement of elastomeric polyurethane reinforced with basalt fiber

In order to overcome compatibility leakage between composite phases, which is a significant challenge in multidimensional composite applications, it is crucial to optimize the chemical nature of additives. The surface of basalt fiber (BF) was chemically enriched via biobased epoxy resin sizing and functional silanization process to improve its interfacial adhesion to the ecograde elastomeric polyurethane (EPU) matrix. The surface properties of BF were examined with the help of scanning electron microscopy X-ray spectroscopy (SEM/EDX) and Fourier-transformed infrared spectroscopy (FTIR) analyses. Impacts of surface modifications were compared based on mechanical, morphological, thermomechanical, and melt-flow behaviors of composites involving pristine and modified BF. Findings revealed that surface-modified BF inclusions improved the tensile strength and Shore-hardness values of composites. Tensile strength of EPU raised from 27.1 to 37.1 MPa after compounding with epoxy-sized BF. Additionally, the resin-coated BF incorporation exhibited a two-fold increase in the tensile modulus of EPU. Thermomechanical response of EPU exhibited an increasing trend by BF inclusions regardless of treatment type. Glass transition temperature of EPU shifted to 5 units higher value with modified BF loadings. SEM investigations confirmed the increased interfacial interaction between the EPU matrix and surface-sized BF. The chemically enriched surface of BF improves composite performance by improving adhesion at the EPU-BF interface. The results of this study confirmed that enhanced interfacial adhesion led to performance improvements for BF-loaded EPU composites.     

Interfacial microstructure and properties of carbon fiber-reinforced unsaturated polyester composites modified with carbon nanotubes

To improve the interfacial properties in carbon fiber (CF)-reinforced unsaturated polyester (UP) composites, we directly introduced functionalized carbon nanotubes dispersed in the fiber sizing onto the fiber surface. For comparing the influence of polymer type on sizing effect, two different polymers (UP MR13006 and water-soluble epoxy (EP)) were used to prepare sizing agent. Morphology and surface energy of CFs were examined by scanning electron microscopy and dynamic contact angle analysis test. Tensile strength was investigated in accordance with ASTM standards. Mechanical properties of the composites were investigated by interlaminar shear strength (ILSS) and impact toughness. Test results indicate that TS, ILSS, and impact toughness were enhanced simultaneously. For UP matrix, the sizing agent containing UP has better reinforcing and toughening effect than the sizing agent containing water-soluble EP.     

Synthesis and characterization of the novel meta‐modified aramid fibers with liquid crystalline properties

To improve the interfacial adhesion between the meta‐aramid fibers and the matrix, the new method of interfacial polymerization was used to complete the aramid's surface modification. Two new kinds of grafted fibers which had liquid crystalline properties were prepared. The structure and properties of the aramid fibers before and after modification were characterized by scanning electron microscope (SEM), Fourier transform infrared, differential scanning calorimetry, and polarizing optical microscope. The surface of grafted aramid fibers was very rough. The range of liquid crystalline phase of the grafted fibers AF‐1 and AF‐2 on the cooling scan, respectively, is from 147 to 209°C and from 163 to 221°C. It was novel that the grafted fibers with rigid‐rod structure had typical nematic texture. The grafted aramid fibers as the ideal substitute material of asbestos were used as reinforcing fibers in nitrile butadiene rubber (NBR) matrix. Combining with NBR, the composites reinforced with the unmodified and grafted aramid fibers were synthesized. The micrographs of the composites' fractured surface were studied by SEM. The mechanical properties of the grafted fibers/NBR composites were superior to the unmodified fibers/NBR composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

碳纤维/聚苯并(噁)嗪复合材料的界面与力学性能的关系研究

本文采用含不同上胶剂的碳纤维与苯并(噁)嗪树脂复合,制备碳纤维/聚苯并(噁)嗪单向复合材料,研究了碳纤维表面上胶剂对于复合材料的层间剪切强度(ILSS)、弯曲性能、断口形貌及动态机械性能的影响.结果表明,含有环氧树脂上胶剂的碳纤维/苯并(噁)嗪树脂基复合材料(EPCF/PBZ)的ILSS和弯曲性能优于含非环氧类树脂上胶剂的碳纤维/苯并(噁)嗪树脂基复合材料(VECF/PBZ)和不含上胶剂的碳纤维/苯并(噁)嗪树脂基复合材料(USCF/PBZ).环氧树脂上胶剂改善了纤维与苯并(噁)嗪树脂的粘结性能,使复合材料的内耗峰峰高降低,能量损耗减小.电镜照片同样验证了这一结果.     

Preparation of emulsion‐type thermotolerant sizing agent for carbon fiber and the interfacial properties of carbon fiber/epoxy resin composite

A modified resin was synthesized through the reaction between dodecylamine and tetraglycidyldiaminodiphenylmethane (TGDDM), which was used as the film former of sizing agent for carbon fiber (CF). The sizing agents were prepared through phase inversion emulsification method. Fourier transform infrared spectroscopy (FTIR) was utilized to analyze the modified resin. Particle sizes of the sizing agents were tested to evaluate their stabilities. Differential scanning calorimetry (DSC) results demonstrated that the glass transition temperature (T_g) of the modified TGDDM is much higher than the T_g of the cured epoxy resin E‐44. The influences of the sizing treatment on CF were investigated by abrasion resistance, fluffs, and stiffness tests. The maximum abrasion resistance increased by 172.8%, compared with the abrasion resistance of the desized CF. Interlaminar shear strength (ILSS) results of the CF/TGDDM composites indicated that the interfacial adhesion between CF and matrix resin was greatly improved after CF was sized. The maximum ILSS value could obtain a 29.16% improvement, compared with the ILSS of the desized CF composite. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41882.     

Amino‐functionalization of carbon fibers through electron‐beam irradiation technique

Amino‐functinonalized carbon fibers were achieved via electron‐beam (EB) irradiation in Diethylenetriamine (DETA) solution and triethylene tetramine (TETA) solution at 200 kGy. Different graft monomer concentrations were investigated to find the optimal concentration of each graft monomer. X‐ray photoelectron spectroscopy, scanning electron microscopy, and Raman spectroscopy were applied to investigate chemical composition and functional groups, topography and disorder degree of amino‐functionalized carbon fibers surface. Meanwhile, adsorption ability and interfacial adhesion between modified carbon fibers and epoxy resin were determined by TGA and interlaminar shear strength (ILSS). It is found that amino‐functionalized carbon fibers which had rougher and more active surface performed better adsorption ability on epoxy resin than untreated fibers. The optimal ILSS values of carbon fiber (treated with DETA and TETA) reinforced composites were 21.37 MPa and 18.28 MPa, which were much higher than that of untreated fiber reinforced composites. The comprehensive results demonstrated that in this condition, the optimal grafting concentrations of both DETA and TETA were 1.5 mol/L. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40274.     

Microstructure and properties of carbon fiber sized with pickering emulsion based on graphene oxide sheets and its composite with epoxy resin

The Graphene oxide (GO) sheets were used for preparing the epoxy resin Pickering emulsion. The particle size and the zeta potential of the Pickering emulsion were measured to evaluate its stability. The stable emulsion could be served as the film former of sizing agent for carbon fiber (CF). The effect of the Pickering emulsion stabilized by GO sheets on the properties of CF and the interfacial adhesion property of CF reinforced composite were investigated. Scanning electron microscopy (SEM) images showed that there existed a layer of sizing agent film with GO sheets evenly on the CF surface. Abrasion resistance and stiffness values of CF were tested and the results indicated that the sized CF conformed to the requirement of CF handleability. The interlaminar shear strength (ILSS) test indicated that the interfacial adhesion of the composite could be greatly improved. The fracture surfaces of CF composites were examined by SEM after ILSS tests. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42285.     

Enhanced interfacial strength and mechanical properties of carbon fiber composites by introducing functionalized silica nanoparticles into the interface

Introducing nanoparticles onto the surface of carbon fibers (CFs) is a useful method for enhancing the quality of fiber-matrix interface. In this work, a liquid sizing agent containing functionalized silica nanoparticles (SiO₂) was well prepared to improve interfacial strength and mechanical properties of composites. In order to enhance the dispersion of SiO₂ nanoparticles in sizing agent, SiO₂ nanoparticles were chemically grafted with 3-aminopropyltriethoxysilane (APS), and then silanized silica (SiO₂-APS) was introduced into the interphase by a conventional sizing process as well. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) confirmed the successful preparation of SiO₂-APS. Scanning electron microscopy (SEM) showed that a uniform distribution of SiO₂-APS on the fiber surface and the increased surface roughness. The sized fibers (CF/SiO₂-APS) exhibited a high surface free energy and good wettability based on a dynamic contact angle testing. Interfacial microstructure and mechanical properties of untreated and sized CFs composites were investigated. Simultaneous enhancements of interlaminar shear strength (ILSS) and impact toughness of CF/SiO₂-APS composites were achieved, increasing 44.79% in ILSS and 31.53% in impact toughness compared to those of untreated composites. Moreover, flexural strength and modulus of composites increased by 32.22 and 50.0% according to flexural test. In addition, the hydrothermal aging resistance of CF/SiO₂-APS composites has been improved significantly owing to the introduced Si-O-Si bonds at the interface.     

Banana/Glass Fiber-Reinforced Polypropylene Hybrid Composites: Fabrication and Performance Evaluation

Hybrid composites of Polypropylene (PP) reinforced with intimately mixed short banana and glass fibers were fabricated using Haake twin screw extruder followed by compression molding with and without the presence maleic anhydride grafted polypropylene (MAPP) as a coupling agent. Incorporation of both the fibers into PP matrix resulted in an increase in tensile, flexural and impact strength with an increasing level of fiber content upto 30 wt% at banana: glass fiber ratio of 15:15 wt% and 2 wt% of MAPP. The rate of water absorption for the hybrid composites decreased due to the presence of glass fiber and coupling agent. The effect of fiber loading in presence of coupling agent on the dynamic mechanical properties has also been analyzed to investigate the interfacial properties. An increase in the storage modulus (E′) of the treated composite indicates higher stiffness. The tan δ spectra confirms a strong influence of fiber contents and coupling agent on the α and β relaxation processes of PP. The nature of fiber matrix adhesion was examined through scanning electron microscopy (SEM) of the tensile fractured specimen. Thermal measurements were carried out employing differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) which indicated a decrease in the crystallization temperature and thermal stability of PP with the incorporation of MAPP treated banana and Glass fiber.     

Thermal characteristics of ethylene‐co‐vinyl acetate/cellulose microfibers composites

Cellulose microfibers were obtained from Hibiscus sabadariffa by steam explosion technique. Structural and surface analysis of the microfibers showed a reduction in diameter and changes in surface morphology from that of raw fibers. The chemical composition of fibers showed increase in α‐cellulose content and decrease in lignin and hemicelluloses for the microfibers. These factors were further confirmed by XRD, SEM, and FTIR results. The CMF were introduced to EVA at different loading by melt extrusion. The composites were analyzed for their thermal stability and phase transition using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA analysis of the composites showed increased onset temperatures for composites compared with pure EVA indicating the superior thermal stability of the composites with fiber loading. DSC analysis shows increase in melting enthalpy and percentage crystallinity with fiber loading increases. Kinetic parameter for the degradation of the composites was obtained using Broido, Coats–Redfern, and Horowitz‐Metzger methods. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Enhanced interfacial adhesion in carbon fiber/poly (acrylonitrile‐butadiene‐styrene) composite through fiber surface treatment by an emulsion sizing

To improve the interfacial adhesion between carbon fiber (CF) and poly(acrylonitrile‐butadiene‐styrene) (ABS) thermoplastic, an emulsion sizing whose film former was a terpolymer N‐phenylmaleimide‐styrene‐maleic anhydride (NSM)/ABS mixture was prepared. NSM, an efficient heat‐resistant modifier for ABS, could make the film former possess a superior heat resistance, which helped the sizing layer maintain integrity during the preparation of CF/ABS composite. Moreover, differential scanning calorimetry (DSC) results demonstrated that the glass transition temperature (T_g) of the NSM modified ABS achieved an improvement of 25.3°C. Particle size and distribution of the sizing agent were investigated to evaluate its stability. The FTIR spectrum obtained demonstrated that the chemical compositions of the sized CF got greatly changed and numerous functional groups appeared on sized CF. Abrasion resistance and fluffs of CF were tested and the results indicated that the sized CF obtained an appreciable enhancement in handleability. Interlaminar shear strength (ILSS) results revealed, after sizing, that the ILSS enhanced by 26.6%, due to the inserted sizing layer between CF and ABS matrix. POLYM. COMPOS., 37:2940–2949, 2016. © 2015 Society of Plastics Engineers     

Influence of diisocyanate,glycidol and polyol molar ratios on the mechanical and thermal properties of glycidyl‐terminated biobased polyurethanes

A series of epoxy‐terminated polyurethanes (EPUs) were synthesized from castor oil, 4,4′‐methylenebis(cyclohexyl isocyanate) (H₁₂MDI) and 2,3‐epoxy‐1‐propanol (glycidol) by changing the molar ratio of H₁₂MDI to glycidol to polyol. Fourier transform infrared, ¹H NMR and solid‐state CP/MAS ¹³C NMR spectroscopic analyses revealed the presence of epoxy linkages within the polyurethane backbone. Thermogravimetric analysis showed that EPU4 with a polyol:diisocyanate:glycidol molar ratio of 1:6:6 exhibited an initial decomposition temperature of 128 °C, which was 26 °C higher than that of EPU1 (1:3:3 molar ratio). Differential scanning calorimetry showed an upward shift in the glass transition temperature with increasing molar ratio. Mechanical analysis demonstrated that the tensile modulus of EPU4 was 7.8 times greater than that of EPU1. The crosslinking densities of EPUs were determined using swelling studies which revealed a gradual increase in crosslinking density with increasing epoxy content within the polyurethane. The morphologies of cryo‐fractured surfaces of EPUs were determined through scanning electron microscopy to analyse the phase dispersion of epoxy and polyurethane. © 2017 Society of Chemical Industry     

The preparation of emulsion type sizing agent for carbon fiber and the properties of carbon fiber/vinyl ester resin composites

Vinyl ester resin emulsion type sizing agent (HMSA‐1) was synthesized by phase inversion emulsification method. Centrifugal sedimentation analysis, particle size analysis, Fourier transforms infrared spectroscopy (FTIR), and gel permeation chromatography were used to characterize HMSA‐1 and Japanese commercial sizing agents (JSA‐1 and JSA‐2). Meanwhile, abrasion resistance, fluffs and breakage, stiffness, scanning electron microscope (SEM) were used to analyze the workability in later process of carbon fiber and surface morphology. The results showed that HMSA‐1 could significantly improve handling characteristics of carbon fiber. SEM micrographs demonstrated that the sized carbon fiber had smooth surface. HMSA‐1 had better compatibility with vinyl ester resin. The interlaminar shear strength (ILSS) of HMSA‐1 sized carbon fiber/vinyl ester resin composite reached the maximum value of 45.96 MPa. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012