The improvement in interfacial shear strength of wood fiber/epoxy composite by sizing with epoxy sizing agent containing MWCNTs

This paper discloses a feasible and high efficient strategy for wood fiber treatment to introducing multi‐wall carbon nanotubes (MWCNTs) to the surface of wood fibers for the aim of improving the interfacial shear strength of wood fiber/epoxy composite. Briefly, a layer of MWCNT was deposited on wood fibers through sizing wood fibers with epoxy sizing agent containing amine‐treated MWCNTs (MWCNT‐PEI). The surface functional groups, morphology, wettability, and interphase properties of MWCNTs on the surface of wood fiber were studied. The remarkable enhancements were achieved in interfacial shear strength of reinforced composites by dipping wood fiber in MWCNTCOOH suspension and wood fiber sizing containing MWCNT‐PEI.     

Preparation of Oxidized Organosolv Lignin⁃based Hydrophilic Sizing Agent and Its Application in Polypropylene北大核心CSCD

The interfacial compatibility of carbon fiber （CF） reinforced composites is the key factor to determine the comprehensive properties of the composites. The sizing agent plays an indispensable role between carbon fibers and matrix resins. Environmentally friendly hydrophilic sizing agent is is a hot research issue to be solved. In this work,the hydrophilic lignin-based sizing agent and carbon fiber reinforced polypropylene （PP） composites are prepared and studied. The lignin is ozonized to increase the reactive group. The obtained lignin reacts with epoxy group to prepare the oxidized organic solvent lignin based epoxy resin（OLBE）. OLBE reacts with alcohol amine and carboxylic acid to obtain the hydrophilic lignin-based sizing agent. KH550 is further added to balance the hygroscopicity of sizing agent. Finally,an oxidized organic solvent lignin-based hydrophilic sizing agent（OLBEDK）with excellent stability was prepared. The CF treated with 2. 5% solid content OLBEDK was only 3. 0 mg. The ILSS,Flexural strength,Flexural modulus and Impact strength of CF/PP composites are increased by 50. 8%,34. 2%,53. 7% and 127. 8%, respectively,compared with those of CF/PP composites without sizing. This is attributed to the π-π conjugation between the benzene ring of lignin and the carbon six-membered ring of CF,and the physical entanglement between the alkyl chain of KH550 and the molecular chain of PP,which enhances the interfacial interaction between CF and PP effectively. © 2022, Science Press (China). All rights reserved.     

原位合成纳米SiO2增强阴离子聚酯型上浆剂及其对碳纤维复合材料层间剪切强度的影响

采用溶胶-凝胶法, 在侧链带有羧基的线性不饱和聚酯中加入正硅酸乙酯(TEOS), 使TEOS在酸性条件下发生水解反应, 原位合成纳米SiO₂增强阴离子型聚酯乳液(SEAPE). 利用傅里叶变换红外光谱(FTIR)仪、 激光粒度分析仪和冷冻扫描电子显微镜(Cryo-SEM)对SEAPE进行分析与表征. 将SEAPE与聚乙二醇单油酸酯润滑剂、 非离子型表面活性剂FC-4430及抗氧剂1010进行复配, 原位制备纳米SiO₂增强阴离子型聚酯乳液上浆剂(SEAPEs), 用扫描电子显微镜(SEM)、 视频动态接触角测量仪、 X射线能谱(EDS)仪和纤维强力仪对SEAPEs上浆后碳纤维的表面形貌、 表面能、 碳纤维(CF)表面元素及碳纤维增强不饱和聚酯(UPR)复合材料(CF/UPR)的层间剪切强度(ILSS)进行测试与表征. 结果表明, 当TEOS添加质量分数为5%时, SEAPEs上浆后的碳纤维有效增强了其与UPR的结合强度, CF/UPR复合材料的ILSS达到40.03 MPa, 与市售环氧树脂型上浆剂上浆后碳纤维增强UPR复合材料相比, ILSS提高90.1%. SEAPEs中原位生成的纳米SiO₂分散均匀, 乳液储存稳定, 上浆后SiO₂均匀吸附在碳纤维表面, 增加碳纤维表面能, 改善碳纤维与树脂间的浸润性, 可有效提高碳纤维增强不饱和聚酯树脂复合材料的ILSS.     

The oxidation‐treated interface on tribological properties of carbon fibers‐reinforced PTFE composite under oil‐lubricated condition

The effect of air oxidation and ozone surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil‐lubricated condition was investigated. Experimental results revealed that ozone treated CF reinforced PTFE (CF–PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air‐oxidated composites. X‐ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that, after ozone treatment, oxygen concentration was obviously increased, and the amount of oxygen‐containing groups on CF surfaces was largely increased. The increase in the amount of oxygen‐containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with PTFE matrix and large scale rubbing‐off of PTFE was prevented, therefore, the tribological properties of the composite were improved. Copyright © 2009 John Wiley & Sons, Ltd.     

The mechanical properties of plasma‐treated carbon fiber reinforced PA6 composites with CNT

The aim of this work is the evaluation of the effects of plasma treatment and the addition of CNT on the mechanical properties of carbon fibre/PA6 composite. A powder impregnation process with integrated inline continuous plasma of carbon fibers was used to produce CF/PA6 composite. CF/PA6 composite was processed into test laminates by compression moulding, and interface dominated composite properties were studied. The tensile and impact strength of composites containing CNT and plasma‐treated carbon fibres improved obviously. The tensile strength of nanocomposite largely increases with the increasing of the CNT content and then decreases when the CNT content is over 2%. The hydroxyl groups of the fibers surface are in favor of the wettability of carbon fibers by the polar matrix resin, which is resulting in a further interaction of the fiber surface with the curing system of the matrix resin.     

The effect of surface modification with nitric acid on the mechanical and tribological properties of carbon fiber‐reinforced thermoplastic polyimide composite

Polyacrylamideacrylate (PAN)‐based carbon fibers were submitted to nitric acid oxidation treatments to improve the interfacial adhesion of the carbon fiber (CF)‐reinforced polyimide (CF/PI) composite. The carbon fiber surfaces were characterized by X‐ray photoelectron spectroscopy (XPS). Nitric acid oxidation not only affects the oxygen concentration but also produces an appreciable change in the nature of the chemical functions, namely the conversion of hydroxy‐type oxygen into carboxyl functions. Nitric acid oxidation treatment modifies the element constituting the fiber, the nitrogen concentration being about 1.2 times higher at the fiber external surface compared to the untreated one. The mechanical and tribological properties of the polymide (PI) composites reinforced by the carbon fibers treated with nitric acid oxidation were investigated. Results showed that the tensile strength of the CF/PI composites improved remarkably due to nitric acid treatment along with enhancement in friction and wear performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Modification effects of short carbon fibers on mechanical properties and fretting wear behavior of UHMWPE composites

The present work comparatively studied the modification effects of short carbon fiber (CF) on the mechanical properties and fretting wear behavior of ultra‐high molecular weight polyethylene (UHMWPE)/CF composites. The interactions between CFs and UHMWPE interface were also investigated in detail. The results showed that, with the increase in fiber content, the compressive modulus and hardness of the composites increased, while its impact strength decreased. It was found that filling of CF can reduce the friction and wear of UHMWPE. In addition, the UHMWPE‐based composites reinforced with nitric acid‐treated CF exhibited better mechanical properties, lower friction coefficient, and higher wear resistance than those of untreated UHMWPE/CF composites. This was attributed to the improvement of interfacial adhesion and compatibility between CF and UHMWPE matrix caused by surface chemical modification of CF. Copyright © 2015 John Wiley & Sons, Ltd.     

Improving the interfacial property of carbon fibre/epoxy resin composites by grafting amine-capped cross-linked poly-itaconic acid

To improve the interfacial properties of carbon fibre-reinforced polymer composites, a surface treatment was used to cap cross-linked poly-itaconic acid onto carbon fibres via in-situ polymerization after itaconic acid grafting. The chemical composition of the modified carbon fiber (CF) surface was characterized by X-ray photoelectron spectral and Fourier-transform infrared spectroscopy. Scanning electron microscopy and atomic force microscopy images showed that the poly-itaconic acid protective sheath was uniformly capped onto the CF surface and that the surface roughness was obviously enhanced. Chemical bonds also played a key role in the interfacial enhancement. The results showed that the interfacial shear strength of the composites with poly-itaconic acid on the carbon fibres (72.2 MPa) was significantly increased by 89.5% compared with that of the composites with pristine CF (38.1 MPa). Moreover, the poly-itaconic acid sheath promoted a slight increase in mono-fibre tensile strength. In addition, the interfacial mechanisms were also discussed. Meanwhile, the mechanical property of the functionalized CF/epoxy resin composites was also significantly improved.     

Increased interfacial adhesion between carbon fiber and poly(vinylidene fluoride) by an aqueous sizing agent

The adhesion behavior of poly(vinylidene fluoride) (PVDF) to carbon fiber (CF) has always been a huge challenge, on account of the inertness nature of PVDF and the lack of reactive functional groups. In this work, a novel maleic anhydride grafted PVDF (MPVDF) aqueous sizing agent was prepared to modify the interface between CF and PVDF matrix. The surface properties of desized, MPVDF‐sized, and PVDF‐sized carbon fibers were characterized by the scanning electron microscopy, X‐ray photoelectron spectroscopy, atomic force microscopy, and dynamic contact angle analysis test. The results demonstrated that the surface roughness increased from 39 to 55 nm, and surface energy increased from 40 to 74 mN m^?1 after MPVDF sizing treatment. The content of activated carbon atoms increased from 31.0% to 48.4%. Subsequently, the interlaminar shear strength was examined, for which was a critical indicator of the interfacial adhesion between CF and matrix. Compared with the desized CF, the value of interlaminar shear strength increased from 14.8 MPa to 25.5 MPa improved by 72% because of the improved H‐bonding formation, surface roughness, and wettability for MPVDF‐sized CF. In addition, the flexural strength and modulus were also improved by 47% and 74%, respectively. Copyright © 2016 John Wiley & Sons, Ltd.     

Tailoring the surface chemistry of carbon fiber and E‐glass composites for improved adhesion

The main challenges in the manufacture of composite materials are low surface energy and the presence of silicon‐containing contaminants, both of which greatly reduce surface adhesive strength. In this study, carbon fiber (CF) and E‐glass epoxy resin composites were surface treated with the Accelerated Thermo‐molecular adhesion Process (ATmaP). ATmaP is a multiaction surface treatment process where tailored nitrogen and oxygen functionalities are generated on the surface of the sample through the vaporization and atomization of n‐methylpyrrolidone solution, injected via specially designed flame‐treatment equipment. The treated surfaces of the polymer composites were analyzed using XPS, time of flight secondary ion mass spectrometry (ToF‐SIMS), contact angle (CA) analysis and direct adhesion measurements. ATmaP treatment increased the surface concentration of polar functional groups while reducing surface contamination, resulting in increased adhesion strength. XPS and ToF‐SIMS showed a significant decrease in silicon‐containing species on the surface after ATmaP treatment. E‐glass composite showed higher adhesion strength than CF composite, correlating with higher surface energy, higher concentrations of nitrogen and C?O functional groups (from XPS) and higher concentrations of oxygen and nitrogen‐containing functional groups (particularly C₂H₃O⁺ and C₂H₅NO⁺ molecular ions, from ToF‐SIMS). Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of surface coating of CNTs on the mechanical properties of CF‐filled HDPE composites

Mechanical properties of carbon fiber (CF) and carbon nanotube (CNT)‐filled thermoplastic high‐density polyethylene (HDPE) composites were studied with particular interest on the effects of filler content and fiber surface treatment by coupling agent. Surface‐treated CF‐filled HDPE composites increased their tensile strength and impact strength, which is further increased with the addition of CNT. SEM showed that CNT‐coating‐treated CF‐HDPE composites show better dispersion of the filler into the matrix, which results in better interfacial adhesion between the filler and the matrix. Copyright © 2014 John Wiley & Sons, Ltd.     

Wettability of carbon fibers modified by acrylic acid and interface properties of carbon fiber/epoxy

The oxidation-reduction and pre-irradiation induced methods were employed to study the effect of acrylic acid modification on the wetting and adsorption ability of carbon fiber (CF) in epoxy solution and the interfacial properties of CF/epoxy. Systematic experimental work was conducted to determine the surface topography, surface energy, surface chemical composition, absorbability and tensile strength of carbon fibers and interfacial adhesion of CF/epoxy before and after modification. The roughness, surface energy, amount of containing-oxygen functional groups and wetting ability were all found to increase significantly after modifications. The tensile strength of carbon fibers was improved marginally by γ-ray pre-irradiation while was decreased little by oxidation-reduction modification. Consequently, the surface modifications of carbon fibers via both oxidation-reduction and pre-irradiation led to an improvement (more than 15%) of the interlaminar shear strength of CF/epoxy composites. The mechanisms of interfacial improvement of modified CF/epoxy composites are proposed.     

Effect of carbon fiber surface functionality on the moisture absorption behavior of carbon fiber/epoxy resin composites

Polyacrylonitrile (PAN)‐based carbon fibers were electrochemically oxidized in aqueous ammonium bicarbonate with increasing current density. The electrochemical treatment led to significant changes of surface physical properties and chemical structures. The oxidized fibers showed much cleaner surfaces and increased levels of oxygen functionalities. However, it was found that there was no correlation between surface roughness and the fiber/resin bond strength, i.e. mechanical interlocking did not play a major role in fiber/resin adhesion. Increases in surface chemical functionality resulted in improved fiber/resin bonding and increased interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy composites. The relationship between fiber surface functionality and the hydrothermal aging behavior of carbon fiber/epoxy composites was investigated. The existence of free volume resulted from poor wetting of carbon fibers by the epoxy matrix and the interfacial chemical structure were the governing factors in the moisture absorption process of carbon fiber/epoxy composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface modification of carbon fiber via electron‐beam irradiation grafting

In this paper, the surface properties of polyacrylonitrile‐based carbon fibers is improved by electron‐beam (EB) irradiation in maleic anhydride/acetone solution at 100, 150, 200 and 150 KGy. Experimental study of this paper is carried out to identify surface topography, surface chemical composition and functional groups, adsorption ability and interface properties of CF/epoxy composites. The results reveal that the roughness of carbon fiber surface is increased obviously after modification by EB irradiation grafting technology. The ratio value of O/C and the relative content of oxygen functional groups on fiber surface are improved effectively, comparing with the unmodified carbon fiber. Besides, adsorption of carbon fiber on epoxy and the mechanical performance of CF/epoxy composites are clearly enhanced after irradiation grafting modification. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation and Properties of Pyrene-Modified Multi- Walled Carbon Nanotube/Epoxy Resin Nanocomposites

Nanocomposites of multi-walled carbon nanotube (MWCNT)/bis-phenol A type epoxy resin were prepared and physical properties of the nanocomposites were investigated. For the fine dispersion of MWCNT in the epoxy resin, MWCNT was modified with pyrene butyric acid (PBA) in the supercritical carbon dioxide (CO₂). The physical adsorption of PBA on the surface of MWCNTs was studied with a thermogravimetric analyzer and a transmission electron microscopy. The electrical surface resistivities of the nanocomposites showed threshold decreases due to percolations above the critical concentration of the MWCNT. The resistivities showed maximum depending on the concentration and the modification of the surface of the MWCNT with PBA. It is postulated that the dispersion of the MWCNT in epoxy resins resulted in dispersion systems which exhibit rheological properties similar to lyotropic liquid crystalline polymers. The surface resistivities of the MWCNT/epoxy systems reflected the morphological characteristics of the systems which also determined rheological properties of the systems.     

Chemical modification on UHMWPE microparticles to improve the interfacial and tribological properties of UHMWPE/carbon fabric/phenolic laminate in water environment

Carbon fabric (CF)/phenolic laminates filled with pristine and chromic acid treated ultra high molecular weight polyethylene (UHMWPE) microparticles were fabricated. Their interfacial and tribological properties in water environment were comparatively investigated. The interlaminar shear strength (ILSS) of the laminates was tested on a universal testing machine (DY35), and the tribological properties were evaluated by a block‐on‐ring tribo‐tester. The worn surfaces and the interfaces of the laminates were respectively analyzed by scanning electron microscope (SEM) and field emission SEM (FESEM). The change of the chemical composition of UHMWPE microparticles after chromic acid etching was analyzed by Fourier transform infrared spectroscopy (FTIR). The chemical state of carbon fiber surface was examined using X‐ray photoelectron spectroscopy (XPS). The results revealed that the chromic acid treated UHMWPE microparticles had more remarkable effect than the pristine ones on improving not only ILSS and wear resistance of CF/phenolic laminate, but also its immunity to water environment. This should be attributed to the strengthened interfaces in treated UHMWPE/CF/phenolic laminate, which were characterized by the drawn dendritic UHMWPE fibrils firmly clinging on the surfaces of carbon fibers and resin in a Boston ivy‐like manner. Copyright © 2015 John Wiley & Sons, Ltd.     

Interface characteristic of aramid fiber reinforced poly(phthalazinone ether sulfone ketone) composite

Interface is an important microstructure for advanced polymer‐matrix composite. The composite interface is the bridge and the link for stress transferring between the fiber and the matrix resin. In this work, oxygen plasma treatment was used for modification of aramid fiber surface. The effects of plasma treatment power on interlaminar shear strength of composite were evaluated by short‐beam shear test. The morphologies of both the aramid fiber surface and its composite interface fracture were observed by SEM. The chemical structure and surface chemical composition of the plasma‐treated and separated fibers were analyzed by Fourier transform infrared (FTIR) and XPS, respectively. The results showed that the interlaminar shear strength of composite was enhanced by 33% with plasma treatment power of 200 W. The FTIR and XPS results indicated that the active functional groups were introduced onto the aramid fiber surface by plasma treatment forming chemical bonds with the poly(phthalazinone ether sulfone ketone) resin. The SEM results proved that the aramid fiber surface was roughened by plasma treatment enhancing the mechanical bond with the poly(phthalazinone ether sulfone ketone) resin. The composite rupture occurred from the composite interface to the fiber or the matrix resin. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of sizing materials of carbon fiber on solid-state cure of poly(p-phenylene sulfide)

The effect of sized carbon fibers on the solid-state cure of poly(p-phenylene sulfide) (PPS) was studied using differential scanning calorimetry. PPS resin reinforced with sized carbon fiber exhibited the largest cure peak for all cure temperatures and showed a second peak at low cure temperature which was absent in both PPS reinforced with desized carbon fiber and neat PPS resin. In a separate experiment in which epoxy prepolymer/PPS mixture was cured, the exothermic reaction was related to the presence of the epoxy sizing used on the carbon fiber. © 1998 John Wiley & Sons, Ltd.     

The dynamic mechanical behavior of random-in-plane short fiber-reinforced epoxy resin composites

In the present paper, the dynamic mechanical properties of random-in-plane short fiber-reinforced epoxy resin composites were studied by using a rheometrics solids analyzer. The three-point bend testing of the four composites (glass fiber/913 epoxy resin, glass fiber/924 epoxy resin, carbon fiber/913 epoxy resin and carbon fiber/924 epoxy resin) was carried out over temperatures from −100°C to 200°C at a frequency of 10 Hz and strain 0.05%. The composites based on 924 epoxy resin, which has been designed specially for high temperature applications, have less energy loss than the 913 epoxy resinbased composites. For the same resin, the carbon fiber-reinforced composites have less energy loss than the glass fiber-reinforced composites. All the composites have less energy loss than their corresponding matrices; the greater the fiber content, the lower the energy loss. The beta transition of 913 epoxy resin has been shifted to a higher temperature after being reinforced. It was shifted from −50°C to −30°C after being reinforced with glass fiber and made a diffuse shoulder-like peak commencing at −30°C after being reinforced with carbon fiber. The 924 epoxy resin has undergone the same change in beta transition as the 913 resin, though to a smaller extent. The phenomenon suggested that interactions between the macromolecules of the epoxy resins and the molecules along the fiber's surface.     

基于电泳沉积法碳纤维表面改性的研究进展及应用

近些年来,碳纤维(CF)由于具有优异的力学性能,被用作复合材料的增强体.但CF表面缺少极性基团,呈现化学惰性,使CF与树脂(EP)之间的界面粘结性能较差.为了改善该问题,需要对CF表面进行改性.氧化石墨烯(GO)和碳纳米管(CNT)具有大的比表面积,且表面含有大量的极性基团,将二者引入CF表面,可以有效改善CF与EP之...