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.     

Preparation and characterization of the modulus intermediate layer in carbon fiber/epoxy composites by depositing sepiolites

An important aspect in development of multi‐scale reinforced composites is their mass production which can be easily realized. In this article, the sepiolites (Si12O30Mg8(OH)4(OH2)4·8H2O) are directly deposited onto the surface of JH‐T800 carbon fibers for the first time with no need for removal of the commercial sizing agent. The sepiolites adhering to the carbon fibers are uniformly distributed with random orientation, and participated in the formation of high modulus intermediate layer encompassing the carbon fiber. After the deposition of sepiolites, the interfacial shear strengths (IFSS) of the carbon fiber/epoxy composites are significantly improved as shown in single‐fiber composite fragmentation tests. Compared to the commercial carbon fiber composites, the sepiolite‐deposited fiber composites also exhibit obvious improvement in the interlaminar shear strength and flexural strength. As a new kind of multi‐scale reinforcement with industrial application value, the sepiolite‐deposited carbon fibers can further raise the level of mechanical properties of the existing carbon fiber reinforced composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43955.     

Interfacial evaluation of epoxy/carbon nanofiber nanocomposite reinforced with glycidyl methacrylate treated UHMWPE fiber

Interface interactions of fiber–matrix play a crucial role in final performance of polymer composites. Herein, in situ polymerization of glycidyl methacrylate (GMA) on the ultrahigh molecular weight polyethylene (UHMWPE) fibers surface was proposed for improving the surface activity and adhesion property of UHMWPE fibers towards carbon nanofibers (CNF)‐epoxy nanocomposites. Chemical treatment of UHMWPE fibers was characterized by FTIR, XPS analysis, SEM, and microdroplet tests, confirming that the grafting of poly (GMA) chains on the surface alongside a significant synergy in the interfacial properties. SEM evaluations also exhibited cohesive type of failure for the samples when both GMA‐treated UHMWPE fiber and CNF were used to reinforce epoxy matrix. Compared with unmodified composite, a ～319% increase in interfacial shear strength was observed for the samples reinforced with both 5 wt % GMA‐grafted UHMWPE and 0.5 wt % of CNF. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43751.     

Evolution of the wettability between carbon fiber and epoxy as a function of temperature and resin curing

This article focuses on experimental studies on the wetting behavior between different carbon fibers (CFs) and epoxy as function of temperature, hardener addition, and progressive curing of the resin. The results indicate that surface sizing plays a key role in wettability of the CF with epoxy. There is a critical temperature for good‐wetting of DGEBA‐DDS mixture/CF. Complete wetting can be obtained for resin/CF after a period of curing time. Moreover, chemical reactions can not only improve the wettability but also strengthen interactions between the curing resin and CF. These results could provide an essential implication for understanding the formation process of interphase region of CF/epoxy composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of rare earth elements surface treatment on tensile properties of aramid fiber‐reinforced epoxy composites

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. Tensile properties of both the aramid/epoxy composites and single fibers were tested. The effects of RES concentration on tensile properties of aramid/epoxy composites were investigated in detail to explore an optimum amount of rare earth elements in solution for modifying aramid fiber. The fracture surface morphologies of tensile specimens were observed and analyzed with the aid of SEM. The experimental results show that rare earth treatment is superior to ECP grafting treatment in promoting interfacial adhesion between the aramid fiber and epoxy matrix. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. The optimum performance is obtained when the content of rare earth elements is 0.5 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1037–1041, 2004     

Effect of processing conditions on wood and glass fiber length attrition during twin screw composite compounding

In this study, we compare the effect of twin-screw extrusion processing on the attrition of wood fibers (WFs) with glass fiber. The effects of process variables and screw design on fiber length were investigated by performing a range of dead-stop experiments where the extruder was stopped, opened-up, and compound removed from the screw elements. Fibers, chemically extracted from the polypropylene matrix, were analyzed for length and width using a commercial fiber analyzer. It was found that WF length attrition and composite properties were less affected by screw design and twin-screw processing conditions (feed rate and screw speed) than glass fiber. Length weighted fiber length and X50 length (a measure used in particle size analysis) were equally correlated with process conditions and composite performance for both fiber types. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48551.     

Effect of polyurethane sizing on carbon fibers surface and interfacial adhesion of fiber/polyamide 6 composites

Commercial epoxy sized carbon fibers (CFs) or unsized CFs have poor interfacial adhesion with polyamide 6 (PA6). Here, CFs are coated with polyurethane (PU) and their surface properties in terms of surface chemistry, contact angle, roughness, and morphology, are investigated. The results of Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy demonstrate PU sizing evidently increases the quantity of polar functional groups on the CFs surface. The surface energy of the PU sized fiber is calculated according to the Owens–Wendt method. Compared with unsized fibers, the contact angle of PU sized fibers is decreased while their total surface energy is increased, indicating superior wettability. Moreover, transverse fiber bundle tests are performed to determine the interfacial adhesion between the CFs and PA6 matrix. The transverse fiber bundle strength of unsized CF is measured to be 12.57 MPa. For PU sized CFs processed with sizing concentration of 1.2%, this value is increased to 24.35 MPa, showing an increase of more than 90%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46111.     

Long jute fiber‐reinforced polypropylene composite: Effects of jute fiber bundle and glass fiber hybridization

Two types of long jute fiber pellet consisting of twisted‐jute yarn (LFT‐JF/PP) and untwisted‐jute yarn (UT‐JF/PP) pellets are used to prepare jute fiber–reinforced polypropylene (JF/PP) composites. The mechanical properties of both long fiber composites are compared with that of re‐pelletized pellet (RP‐JF/PP) of LFT‐JF/PP pellet, which is re‐compounded by extrusion compounding. High stiffness and high impact strength of JF/PP composites are as a result of using long fiber. However, the longer fiber bundle consequently affects the distribution of jute fiber. The incorporation of 10 wt % glass fibers is found to improve mechanical properties of JF/PP composites. Increasing mechanical properties of hybrid composites is dependent on the type of JF/PP pellets, which directly affect the fiber length and fiber orientation of glass fiber within hybrid composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41819.     

Atmospheric pressure plasma jet treatment of wheat straw for improved compatibility in epoxy composites

The aim of this study was to investigate the effects of an atmospheric‐pressure gas plasma jet treatment on the interior and exterior surface characteristics of wheat straw and on the mechanical properties of epoxy composites reinforced with wheat straw. Dry air was used as the process gas in the plasma system. A distance between the nozzle and the substrate surface (DNSS) of 35 mm was determined as the most effective parameter enabling remarkable decreases in the (surface energy) values of both the interior and exterior surfaces of virgin wheat straw. Increased intensities of the peaks related to carbon‐rich species and 11% to 43% decreases in the oxygen/carbon ratios on the surfaces confirmed the more hydrophobic nature of the plasma‐treated wheat straw. A further increase in the DNSS decreased the effectiveness of the plasma treatment, while a decrease in the DNSS caused an inverse effect on the value, probably due to the etching effect of the plasma action, which was supported by the atomic force microscopy analysis. The overall results indicated that the increased hydrophobicity and valley‐like occurrences without sharp pits created by the plasma action improved the compatibility of the wheat straw with the epoxy matrix, which contributed to superior mechanical properties of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45828.     

Scrutinizing the influence of strain‐induced fiber orientation on the melt rheological behavior of short aramid fiber/thermoplastic elastomer composite using rubber process analyzer

The effect of fiber loading and its orientational changes on the melt rheological behavior of a short aramid fiber reinforced ethylene‐octene copolymer was explored as function of dynamic strain and frequency using a Rubber Process Analyser (RPA). The rheological responses such as the storage modulus and complex viscosity to a cyclic dynamic strain sweep and subsequent linear viscoelastic (LVE) frequency sweep were performed to probe the orientational changes of the short fiber within the sample. An enhanced elastic shear modulus was observed at the low strain regime with a few numbers of repeated strain sweeps and level off thereafter. This can be attributed to the orientational changes of the short fiber from an initial random orientation to a well‐ordered concentric fiber string and the string–string packing with repeated oscillatory shear strain. The complex viscosity measured as a function of LVE frequency sweep having the influence of a pre strain history was also found to increases in first few cycles, but very interestingly the complex viscosity measured at all the frequency sweep cycles shows similar values, which are not subjected to any strain history. The optical microscopic images of the samples before and after the RPA analyses clearly support the possibility of fiber orientations and their subsequent packing with repeated strain sweeps. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The single fiber composite test: A comparison of E‐glass fiber fragmentation data with statistical theories

Novel difunctional and tetra functional organically modified ceramics with methacrylate functional groups were developed from liquid precursors using the sol–gel process. These novel inorganic–organic hybrid materials were characterized using various techniques and used for the preparation of visible light cure dental restoratives, which have good mechanical properties and excellent surface hardness. Effect of cure time on vickers hardness of cured composite was measured, and compared with that of the bisphenol A glycidyl methacrylate (Bis GMA) based composite. Statistical evaluation using analysis of variance (single factor) showed a significant (P < 0.05) difference in diametral tensile strength and hardness with variation in inorganic content. Also a significantly improved hardness was obtained for the new organically modified ceramic composite compared with BisGMA based composite at all exposure time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of crystallization behavior of neat poly(vinylidene fluoride) and transcrystallization in carbon fiber/poly(vinylidene fluoride) composite under a temperature gradient

The crystallization behavior of poly(vinylidene fluoride) (PVDF) and transcrystallization in carbon fiber (CF)/PVDF composite were investigated under a temperature gradient. The crystallization temperature (T_c) was controlled in the range of 110–180 °C. For neat PVDF, the results showed that exclusive γ phase formed at T_c above 164 °C, but coexisted with α phase at T_c ranging from 137 to 160 °C. The promotion of γ phase to nucleation of α phase at low T_c was observed for the first time. For CF/PVDF composite, a cylindrical transcrystalline (TC) layer formed on the surface of CF when T_c was between 137 and 172 °C. The TC layer was exclusively composed of γ phase at T_c above 164 °C. The hybrid nucleation was dominated by γ phase though some α phase nuclei emerged on the surface of CF when T_c was in the range of 144–160 °C. As T_c decreased, competition between the hybrid nucleation of α and γ phase became more intense. The γ phase nuclei was soon circumscribed by the rapidly developed α phase when T_c was below 144 °C. Furthermore, some α phase nuclei were induced at the surface of the γ phase TC layer, and developed into α phase TC layer when T_c was in the range of 146–156 °C, which resulted in a doubled TC layer of α and γ phase at the interface of the composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43605.     

Effect of polyurethane sizing agent on interface properties of carbon fiber reinforced polycarbonate composites

This work is aimed at investigating how molecule structure of polyurethanes (PUs) as sizing agents influence the interface properties of carbon fiber (CF) reinforced polycarbonate (PC) composites. Effects of four PUs as sizing agents for CF on the interlaminar shear strength (ILSS) of CF reinforced PC composites are investigated. It is found that the three PUs except PC–PU as sizing agents on oxidized CF (OCF) made the ILSS of their reinforced PC composites increase up to 62.9 MPa by more than 24.8%. The chemical interaction between PU sizing agents and CF are attributed to high reactivity of isocyanate, but carbonate groups on PC–PU may have a chain unzipping reaction due to active groups on the surface of OCF. The chemical interaction between PU sizing agents and PC are attributed to transesterification. As a result, PUs containing isocyanate or polyester groups are ideal sizing agents for CF reinforced PC composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47982.     

挤出机头内流场对玻纤取向和分布的影响

本文分析了平直和发散两种挤出机头内的流场,推得发散流道内熔体周向拉伸应变速率的表达式;研究了两种挤出流率下由这两种机头挤出的制品壁内玻纤的取向和分布,并通过流道内的剪切和周向拉伸应变速率,对玻纤取向和分布的形成机理进行解释。结果表明：经平直机头挤出的制品内,玻纤在剪切作用下基本沿流动方向排列。发散机头内熔体受剪切和周向拉伸的共同作用,使制品壁厚方向形成了“表层-次表层-芯层-次表层-表层”的五层结构,并首次发现芯层呈“W”形排列。玻纤的排列不仅受流动过程中的应变影响,更取决于应变速率的大小。     

Effect of fiber/matrix chemical modification on the mechanical properties and water absorption of extruded flax/polypropylene composite

Compound of flax/polypropylene (PP) is characterized concerning the mechanical properties of stiffness, strength, and impact in addition to the water absorption behavior. Manufacturing takes place by twin‐screw extruder. The extruder screw layout is modified through different kneading elements to get high fiber aspect ratio. Sodium hydroxide solution was used as a washing solution for the flax fibers' surfaces. Both fiber and matrix are chemically modified. Selected groups of the fibers were further treated using trimethoxyvinylsilan TMVS and acrylic acid AA. The PP matrix is also treated with different coupling agents; namely, maleated PP MAPP, TMVS‐MAPP, and acrylic acid‐functionalized PP AAPP. The combinations of different fiber/matrix are extruder compounded, injection molded, and finally tested. Fiber modification seems to be positive with AA‐modified surface. AAPP matrix modification improves the stiffness four times that of the untreated flax/PP. Till 30 and 40 wt %, the more the fiber is the more the strength and stiffness, respectively. MAPP‐modified matrix improves the mechanical properties and keeps low water absorption values. AAPP‐modified matrix shows the best stiffness values. TMVS‐MAPP does not seem to have distinguished improvement compared with MAPP. NaOH‐TMVS/MAPP and NaOH‐TMVS/AAPP systems can serve as alternatives to the normal NaOH/MAPP treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Reaction of carbon fiber sizing and its influence on the interphase region of composites

What might happen with the interphase region of composite if the sizing agent cannot afford the attack of processing temperature and firstly reacted before its combination with the resin, is rarely reported. On the basis of this, herein, effects of sizing reaction on the interphase region of composite were investigated, as well as on the carbon fiber surface properties. It showed that the interfacial shear strength of carbon fiber/epoxy composite was improved after the sizing reaction. The interphase modulus was also increased with a thinner gradient distance. Further analysis indicated that the fiber surface roughness increased, the fiber wettability with the resin lowered, and the chemical reactions between sizing agent and resin reduced after 200°C/2 h treatment on carbon fiber. These results explained the change of the interphase region, which are meaningful for sizing optimization. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41917.     

Effects of alkalization and fiber loading on the mechanical properties and morphology of bamboo fiber composites. II. Resol matrix

Resol resin composites reinforced with alkali‐treated bamboo strips were fabricated with a hand‐lay‐up technique. This study was aimed at the evaluation of the influence of the caustic concentration on the mechanical properties of bamboo‐strip‐reinforced resol composites with a constant 50% loading of the reinforcement. The treatment of bamboo fiber in a solution of sodium hydroxide with increasing concentration percentages resulted in more and more rigid composites; as a result, the strength and modulus values exhibited improvements. The maximum improvement in the properties was possibly achieved with 20% caustic treated reinforcements. An infrared study indicated the formation of aryl alkyl ether with ? OH groups of cellulose and methylol groups of resol. Beyond 20%, there was degradation in all the strength properties due to the failure of the mechanical properties of the reinforcement itself. A correlation was found to exist between the mechanical properties and the morphology that developed. Another set of composites with variable loadings of 20% alkali treated fiber (40, 50, and 60%) was fabricated, and a 60% fiber loading showed the best mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of fiber orientation on surface characteristics of C/SiC composites by laser-assisted machining

In this paper, the characteristics and mechanism of laser-assisted machining (LAM) of C/SiC composites with different fiber orientations (0°, 45°, 90°, 135°) are studied. For the purpose of this study, a series of LAM experiments have been carried out and supported by a comparative analysis over the conventional machining (CM). Furthermore, the effect of fiber orientation on surface morphology, roughness, and sub-surface damage was explored. It is found that the surface quality of the workpiece treated by LAM is better than that of CM, and a lower surface roughness Ra value is obtained. It is shown that depending on different fiber orientations, the surface roughness decreases in different degrees. The roughness at 90° fiber orientation witnesses the maximum reduction, followed by 0° and 45° fiber orientation, and the roughness at 135° fiber orientation undergoes the slightest reduction. Moreover, surface micro-defects under LAM are significantly reduced, and fiber fractures are tidier. On the other hand, the matrix is mixed with fiber debris under high temperatures and sticks to the machined surface, filling and repairing surface pits and holes and hence improving the processed surface quality. These results provide new guidance for improving the machining quality of C/SiC composites.     

Synthesis and characterization of novel epoxy-modified waterborne polyurethanes and their use in carbon fiber sizing

Novel epoxy-modified waterborne polyurethanes (EPUs) were synthesized from toluene 2,4-diisocyanate, poly(ethylene glycol) (PEG), dimethylolbutyric acid, and 2,3-epoxy-1-propanol (glycidol). The chemical structures of the EPU products were characterized by ¹H-NMR and Fourier transform infrared spectroscopy. The thermal properties of the EPUs were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA showed that the EPUs had good thermal stability, with an initial decomposition temperature higher than 250°C. DSC analysis showed that the glass-transition temperature of EPU1 was higher than that of EPU2. When the EPUs were heated above 150°C, the curing reaction took place. In this study, the EPUs were used for carbon fiber sizing. The mechanical interfacial strength between the fibers and the matrix was evaluated by scanning electron microscopy (SEM) and interlaminar shear strength (ILSS) testing. The SEM images of the fracture sections of the composites proved that the interfacial adhesion between the fibers and the matrix improved after the EPU sizing treatment. The composites exhibited the highest value of ILSS after the EPU1 sizing treatment. The excellent properties of the EPUs confer it with potential applications in carbon fiber sizing. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

表面处理对玻纤/碳纤增强橡胶基密封复合材料性能的影响

采用压延成张工艺制备碳纤维和玻璃纤维混杂增强非石棉橡胶基密封复合材料(NAFC),以横向抗拉强度作为表征混杂增强橡胶基密封材料中纤维与橡胶界面粘结性能的指标.通过扫描电镜(SEM)对材料横向拉伸试样断口进行形貌分析,及对材料的耐油、耐酸、耐碱性能进行测试,探讨了不同表面处理工艺对纤维与基体界面粘结效果的影响.研究结果表明,对玻璃纤维采用偶联剂KH-550浸渍后涂覆环氧树脂涂层,对碳纤维在空气氧化后涂覆环氧树脂涂层,可有效增强纤维、基体的界面粘结,所制得的混杂纤维增强复合材料具有较好的机械性能和耐介质性能.