Improvement of adhesion of Kevlar fiber to epoxy by chemical modification

Kevlar 149 fibers were surface-modified by chlorosulfonation and subsequent reaction of -SO₂O with some reagents (e.g. glycine, water, ethylenediamine, and 2-butanol) to improve the adhesion to epoxy resin. The mechanical properties and surface topography of the modified fibers were investigated at different reaction times and reagent concentrations. The surface functional groups introduced into the surface of the fibers were identified by X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectroscopy (SIMS). The interfacial shear strength (IFSS) between the fibers and epoxy resin was measured by the microbond test. The results showed that the IFSS was markedly improved (by a factor of 2.25) by the chlorosulfonation/glycine treatment and that the fiber strength was not affected. Scanning electron microscopy (SEM) was also used to study the surface topography of fibers pulled from the epoxy resin. Furthermore, energy dispersive X-ray (EDX) spectroscopy was used to qualitatively examine the amount of sulfur in the fiber surfaces and in the fracture surfaces of fibers from microbond pull-out specimens. The results of EDX examination were consistent with a change of the fracture mode from the interface between the fiber and the epoxy resin to a location within the fiber and/or epoxy resin as observed by SEM.     

Interfacial strength measurements in poly(p-phenylene benzobisthiazole)/epoxy composites

A micromechanical study of the behaviour of poly(p-phenylene benzobisthiazole) ( )/epoxy interfaces is performed using two testing procedures, the droplet micropull-out test, and a version of the fragmentation test in which the stress and strain are continuously monitored by optical microscopy and video recording. Since very few interfacial strength data are currently available for /epoxy composites, it is the purpose of our study to generate such data for this system. The fragmentation phenomenon in /epoxy is found to be complex and more difficult to interpret than in brittle fibre composite systems, due to the fibrillation failure mode of the fibre. The interfacial shear strength value based on the fragmentation test is 17.3 MPa, approximately twice the value measured with the droplet micropull-out test.     

The effects of surface treatments of fibers on the interfacial properties in single-fiber composites

The interfacial properties between fibers and the matrix contribute to the overall properties in high performance composites. Plasma treatments (Ar, O₂, CF₄/O₂, N₂/H₂) have been performed on carbon fibers to improve the fiber-matrix interaction. The treatment efficiency was checked by the single-fiber technique, while the surface chemistry and morphology were characterized by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectroscopy (SSIMS), and scanning electron microscopy (SEM). The O₂- and N₂/H₂-plasma treatments proved most effective both for introducing oxygen-containing functionalities at the fiber surface and for improving the interfacial shear strength of carbon fiber/epoxy composites. A relationship between the oxygen concentration at the fiber surface and the interfacial shear strength is demonstrated.     

Effects of surface modification by remote hydrogen plasma on adhesion in poly(tetrafluoroethylene)/copper composites

Poly(tetrafluoroethylene) (PTFE) sheet was modified with the remote hydrogen plasma, and the effect of the modification on adhesion between the PTFE sheet and copper metal was investigated. The remote hydrogen plasma was able to make PTFE surfaces hydrophilic without etching. In the modification process, defluorination and oxidation occurred on the PTFE surface. Reactivity of defluorination was 25% (estimated from the concentration of CF₂ component) −39% (estimated from the F/C atom ratio). Surface modification of PTFE surface by remote hydrogen plasma contributed to the adhesion between PTFE and copper metal. Peel strength was improved from 7.5 to 92 mN/5 mm by surface modification by a factor of 12. Failure of the PTFE/copper adhesive joint occurred at the interface between the PTFE and copper metal layers, rather than in the inner layer of the PTFE polymer or copper metal layers. Remote hydrogen plasma treatment is a preferable pretreatment of PTFE surface for the fabrication of PTFE and copper metal composites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2191–2200, 1999     

常压等离子体改善高性能纤维粘结性的研究

以氦气为载气,氧气为反应气体,对高强度聚乙烯和Twaron 1000芳纶两种高性能纤维进行常压等离子体处理,来改善纤维的粘结性能;采用单纤维抽拔实验测定等离子体处理前后纤维与环氧树脂之间的界面剪切力;利用原子力显微镜和X射线光电子能谱仪分析等离子体处理前后纤维表面形态和化学成分的变化。结果表明:高强度聚乙烯纤维和芳纶经常压等离子体处理后,纤维表面粗糙度增加,纤维表面碳元素含量下降,羟基、羧基等含氧或氮的极性基团增加,纤维粘结性能得到提高,但其强度无明显变化。     

Measurement of Adhesion Between Carbon Fibers and Bismaleimide Resins

The adhesion between carbon fibers and bismaleimide resins was evaluated using the microbond single fiber pull-out test. A commercially-available, methylene dianiline-based bismaleimide resin and a novel phosphorus-containing bismaleimide were tested with as-received and plasma-treated polyacrylonitrile-based carbon fibers. The surface chemical composition, topography, tensile strength, and surface free energy of the carbon fibers were studied using x-ray photoelectron spectroscopy, scanning electron microscopy, single fiber tensile tests, and dynamic contact angle analysis. The carbon fiber-bismaleimide adhesion improved when the carbon fiber received an oxidative commercial surface treatment or was exposed to an air or ammonia plasma prior to bonding.     

Measurement of Adhesion Between Carbon Fibers and Bismaleimide Resins

The adhesion between carbon fibers and bismaleimide resins was evaluated using the microbond single fiber pull-out test. A commercially-available, methylene dianiline-based bismaleimide resin and a novel phosphorus-containing bismaleimide were tested with as-received and plasma-treated polyacrylonitrile-based carbon fibers. The surface chemical composition, topography, tensile strength, and surface free energy of the carbon fibers were studied using x-ray photoelectron spectroscopy, scanning electron microscopy, single fiber tensile tests, and dynamic contact angle analysis. The carbon fiber-bismaleimide adhesion improved when the carbon fiber received an oxidative commercial surface treatment or was exposed to an air or ammonia plasma prior to bonding.     

高性能有机纤维表面等离子体改性研究

在各种纤维表面改性方法中,等离子体改性方法具有操作简单,效率高,节省能源,无公害等特点,是近年来研究的热点.本文综述了各种等离子表面改性技术在高性能纤维表面改性中的应用和研究进展情况,并指出了其进一步的发展趋势.     

碳纤维表面处理的新方法

碳纤维表现处理是为了改善表面形态结构和表面化学环境,提高表面能,强化与基体树脂两相界面之间的粘接,从而达到提高复合材料层间剪切强度（ILSS）的目的。     

Influence of moisture regain of aramid fibers on effects of atmospheric pressure plasma treatment on improving adhesion with epoxy

One difference between a low‐pressure plasma treatment and an atmospheric pressure plasma treatment is that in the atmosphere, the substrate material may contain significant quantities of moisture, which could potentially influence the effects of the plasma treatment. To investigate how the existence of moisture affects atmospheric pressure plasma treatment, aramid fibers (Twaron 1000) with three different moisture regains (0.5, 4.5, and 5.5%) were treated by an atmospheric pressure plasma jet for 3 s at a gas flow rate of 8 L/min, a treatment head temperature of 100°C, and a power of 10 W. The scanning electron microscopy analysis showed no observable surface morphology change for the plasma treated samples. X‐ray photoelectron spectroscopy analysis showed the oxygen contents of the 0.5 and 4.5% moisture regain groups increased from that of the control, although the opposite was true for the 5.5% moisture regain group. The advancing contact angles of the treated fibers decreased about 8°–16° whereas their receding contact angles decreased about 17°–27°. The interfacial shear strengths of the treated fibers as measured using microbond pull‐out tests were more than doubled when the moisture regain was 4.5 or 5.5%, whereas it increased by 58% when the moisture regain was 0.5%. In addition, no significant difference in single fiber tensile strength was observed among the plasma treated samples and the control sample. Therefore, we concluded that moisture regain promoted the plasma treatment effect in the improvement of the adhesion property of aramid fibers to epoxy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 242–247, 2006     

介质阻挡放电在芳纶表面改性中的应用

综述了介质阻挡放电应用于芳纶表面改性研究的最新进展;介绍了介质阻挡放电的机理、特点以及国内主要的介质阻挡放电等离子体的设备;阐述了介质阻挡放电对芳纶亲水性能和粘结性能等表面性能的改善。指出芳纶等离子体表面改性的时间效应限制了其广泛应用,应进一步加强纤维表面等离子体改性的机理研究。     

Plasma etching and plasma polymerization coating of carbon fibers. Part 1. Interfacial adhesion study

Unsized AS-4 carbon fibers were etched by RF plasma and then coated via plasma polymerization in order to enhance their adhesion to vinyl ester resin. Gases utilized for plasma etching were Ar, N₂ and O₂, while monomers used in plasma polymerization coating were acetylene, butadiene and acrylonitrile. Plasma etchings were carried out as a function of plasma power (30–70 W), treatment time (1–10 min) and gas pressure (20–40 mtorr). Plasma polymerizations were performed by varying the treatment time (15–60 s), plasma power (10–30 W) and gas pressure (20-40 mtorr). The conditions for plasma etching and plasma polymerization were optimized by measuring interfacial adhesion with vinyl ester resin via micro-droplet tests. Plasma etched and plasma polymer coated carbon fibers were characterized by SEM, XPS, FT-IR and α-Step, dynamic contact angle analyzer (DCA) and tensile strength measurements. In Part 1, interfacial adhesion of plasma etched and plasma polymer coated carbon fibers to vinyl ester resin is reported, while characterization results including tensile strength of carbon fibers are reported in Part 2. Among the treatment conditions, a combination of Ar plasma etching and acetylene plasma polymer coating provided greatly improved interfacial shear strength (IFSS) of 69 MPa, compared to 43 MPa obtained from as-received carbon fiber. Based on the SEM analysis of failure surfaces and load-displacement curves, the failure was found to occur at the interface between plasma polymer coating and vinyl ester resin.     

Surface modification of poly(tetrafluoroethylene) film by chemical etching,plasma, and ion beam treatments

Chemical etching, plasma, and ion beam treatments were used to modify the surface of Polytetrafluoroethylene (PTFE). Each surface treatment method developed different surface characteristics. In addition to morphological observation, contact angle, atomic chemical composition, and adhesion strength were measured after treatment with various methods. The different adhesion strengths were explained based on the morphology and atomic chemical composition of the treated PTFE surfaces. The chemical etching showed substantial defluorination, and the adhesion strength was fairly high. The argon plasma treatment introduced very large amounts of oxygen into the surface, and the surface was very smooth with a crater‐like structure. Ion beam treatment induced a form of spires whose dimensions were of several micrometers, depending on the ion dose, whereas the oxygen plasma‐treated samples showed short spires with spherical particles on the top. The spire‐like surface morphology and increased surface area during bonding by ion beam treatment appear to be the reason for a higher adhesion strength than that of the oxygen plasma‐treated PTFE. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1913–1920, 2000     

氩等离子体处理聚四氟乙烯粘接性能研究

利用氩等离子体表面处理后再经丙烯酸化学接枝处理方法对聚四氟乙烯(PTFE)薄片表面进行改性,发现PTFE对水的润湿性明显改善,然后用环氧胶进行粘接,其粘接强度有较大提高。     

常压辉光放电等离子体研究进展及聚合物表面改性

综述了常压辉光放电等离子体(APGDP)的产生机理及研究进展。介绍了难以产生稳定的APGDP 是由于辉光放电容易向细丝放电和弧光放电过渡,其解决措施是选择合适的介质板材料、电极间距、电源电压及频率、气体成分等。指出APGDP对化纤聚合物表面改性的效果与聚合物的分子结构、等离子体气体、介质板材料等因素有关,且改性效果具有时效性,要根据聚合物的分子结构选择合适的等离子体。     

Influence of surface treatment of carbon fibers on interfacial adhesion strength and mechanical properties of PLA‐based composites

In the present study C/PLA composites with different fiber surface conditions (untreated and with nitric acid oxidation for 4 h and 8 h) were prepared to determine the influence of surface treatment on the interfacial adhesion strength and mechanical properties of the composites. A chemical reaction at the fiber–matrix interfaces was confirmed by XPS studies. Nitric acid treatment was found to improve the amount of oxygen‐containing functional groups (particularly the carboxylic group, —COOH) on carbon fiber surfaces and to increase the surface roughness because of the formation of longitudinal crevices. The treated composites exhibited stronger interface adhesion and better mechanical properties in comparison to their untreated counterparts. There was a greater percentage of improvement in interfacial adhesion strength than in the mechanical properties. The strengthened interfaces and improved mechanical performance have been mainly attributed to the greater extent of the chemical reaction between the PLA matrix and the carbon fibers. The increased surface roughness also has had a slight contribution. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 367–376, 2001     

The effect of TiO2 morphology on the surface modification of poly (ethylene terephthalate) for electroless plating

In this study, a surface modification of the poly (ethylene terephthalate) (PET) film using TiO₂ photocatalytic treatment was investigated. In order to enhance the adhesion strength between the PET film and the electroless copper film, the effects of TiO₂ crystal forms, TiO₂ particle sizes, and TiO₂ content, as well as treatment condition, upon the surface contact angle, surface characterization, and adhesion strength were investigated. Anatase TiO₂ with a particle size of 5 nm had a high catalytic activity and dispersibility in aqueous solution. After the optimal photocatalytic treatment, the surface contact angle of the PET film decreased from 84.4° to 19.8°, and the surface roughness of the PET film increased from 36 to 117 nm. The adhesion strength between the PET film and the electroless copper film reached 0.89?KN?m^?1. X-ray photoelectron spectroscopy analyses indicated the carbonyl group was formed on the PET surface after photocatalytic treatment, and the surface hydrophilicity was improved. Consequently, TiO₂ photocatalytic treatment is an environmentally friendly and effective method for the surface modification of the PET film.     

Effect of DC glow discharge treatment on the surface energy and surface resistivity of thin film of polypropylene

A change in the surface energy and surface resistivity of a thin film of polypropylene (PP) of thickness 100 μm was investigated, using direct current (DC) glow discharge. The thin film of the PP was treated for various discharge powers and treatment time and the modification in the surface energy and the surface resistivity was observed. To investigate the modification in the surface energy after DC glow discharge treatment, contact angle of two test liquids formamide and de‐ionized water over the surface of PP film was measured. By measuring the contact angle the change in surface energy and its two polar and dispersive components have been measured. It was observed that at a given power level of DC glow discharge surface energy and its polar component increases with increase of the treatment time, attains a maximum value, and then becomes almost constant. Correspondingly, with increase in surface energy, a decrease in surface resistivity was observed. Also, a change in surface morphology was observed by atomic force microscopy and by FT‐IR spectra generation of polar groups at the surface of PP film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 767–772, 2007     

空气介质阻挡放电等离子体对国产芳纶ⅢA表面改性的研究

采用空气介质阻挡放电等离子体对国产芳纶ⅢA进行表面处理,优化了其处理工艺。用SEM、XPS等方法研究了处理前后纤维表面形态和化学状态的变化,通过短梁剪切试验评价了芳纶ⅢA/环氧复合材料的抗层间剪切强度。结果表明:经空气等离子体处理后芳纶ⅢA表面粗糙度增加,极性增强,纤维力学性能无明显变化,芳纶ⅢA/环氧复合材料的抗层间剪切强度提高了18%。     

PBO纤维表面改性的研究进展

聚对苯撑苯并双噁唑(PBO)由于其特殊的表层结构,与聚合物树脂基体复合时存在严重的界面不相容性。简要介绍了PBO纤维的结构与性能,综述了化学刻蚀、偶联剂处理、等离子体处理、电晕处理、辐射处理、酶处理、热处理、化学涂层和超临界液体处理等PBO纤维表面改性方法。