Plasma surface modification of advanced organic fibres

A marked improvement in the interlaminar shear strength and flexural strength of aramid/ epoxy composites is observed when the fibres are pretreated in an ammonia or ammonia/ nitrogen gaseous discharge (plasma) to introduce amine groups on to the fibre surface. Scanning electron and optical microscopic observations are used to examine the microscopic basis for these results. Scanning electron micrographs of shear fracture surfaces show clean fibre/matrix separation in composites made from untreated fibres, indicative of weak interfacial bonding. In contrast, shear fracture surfaces of composites containing plasma-treated fibres exhibit clear evidence of fibre fibrillation and matrix cracking, suggesting stronger interfacial bonding. Optical microscopic examination of flexure specimens shows that enhanced strength results mainly from reduced compressive fibre buckling and debonding, due to an increase in fibre/matrix interfacial bond strength. This increase is not accompanied by any significant change in the interlaminar fracture energy or flexural modulus of the composites, but there is an appreciable loss in transverse ballistic impact properties. These results are also examined in terms of the observed increase in fibre/matrix interfacial strength.     

Plasma surface modification of advanced organic fibres

The interlaminar shear strength, interlaminar fracture energy, flexural strength and modulus of extended-chain polyethylene/epoxy composites are improved substantially when the fibres are pretreated in an ammonia plasma to introduce amine groups on to the fibre surface. These property changes are examined in terms of the microscopic properties of the fibre/matrix interface. Fracture surface micrographs show clean interfacial tensile and shear fracture in composites made from untreated fibres, indicative of a weak interfacial bond. In contrast, fracture surfaces of composites made from ammonia plasma-treated fibres exhibit fibre fibrillation and internal shear failure as well as matrix cracking, suggesting stronger fibre/matrix bonding, in accord with the observed increase in interlaminar fracture energy and shear strength. Failure of flexural test specimens occurs exclusively in compression, and the enhanced flexural strength and modulus of composites containing plasma-treated fibres result mainly from reduced compressive fibre buckling and debonding due to stronger interfacial bonding. Fibre treatment by ammonia plasma also causes an appreciable loss in the transverse ballistic impact properties of the composite, in accord with a higher fibre/matrix interfacial bond strength.     

Plasma surface modification of advanced organic fibres: Part V Effects on the mechanical properties of aramid/phenolic composites

Aramid fibres have been treated in ammonia and oxygen plasma to enhance adhesion to resole phenolic resins. The plasma treatments resulted in significant improvements in interlaminar shear strength (ILSS) and flexural strength of composites made from these materials. Composites containing aramid fibres with epoxide groups reacted on to the ammonia plasma-treated fibre surface also showed further improvements in ILSS and flexural strength. Scanning electron and optical microscopic observations were used to examine the microscopic basis for these results, which have been compared with those obtained previously for aramid/epoxy and aramid/vinyl ester composites. For composites containing oxygen and ammonia plasma-treated fibres, the enhanced ILSS and flexural strength are attributed to improved wetting of the surface-treated aramid fibres by the phenolic resin. However, for those containing fibres with reacted epoxide groups on the ammonia plasma-treated fibre surfaces, the enhanced composite properties may be due to covalent chemical interfacial bonding between the epoxide groups and the phenolic resin. Effects of catalyst levels and cure cycle on the ILSS of composites laminated with untreated fabric has also been examined and optimum values have been determined. The catalyst concentration has an influence on the phase-separated water domain density in the matrix which in turn, affects the available fibre/matrix bonding area and hence the composite ILSS and flexural strength. This revised version was published online in November 2006 with corrections to the Cover Date.     

FEP纤维的等离子体表面改性

以空气气氛对聚全氟乙丙烯（FEP）纤维进行等离子体处理,利用SEM、DSC、XPS对改性前后纤维的性能及形貌进行表征,并测试水在纤维表面的接触角。等离子体处理后纤维的表面发生了C—F键断裂,表面形貌变得粗糙,O原子含量增加4.65%,F原子含量降低4.37%,O/C、F/C原子含量比分别由0.19和0.28变为0.25和0.22,但DSC结果表明结晶度未发生变化;水在纤维表面的接触角由改性前的112.3°降至改性后的54.1°,纤维亲水性得到明显增强。     

PBO纤维表面等离子体接枝改性研究

采用等离子体接枝改性方法对PBO纤维表面进行改性研究，利用AFM分析改性前后纤维表面的形貌变化，测试了改性前后纤维表面浸润性变化，并采用Microbond方法表征了纤维与树脂基体的界面IFSS。结果表明：等离子体接枝后纤维表面引入了活性基团，纤维浸润性改善；在100W、10min接枝条件下IFSS提高了75％。     

Plasma surface treatment and modification of glass fibers

New helical coupling plasma system for continuous surface treatment and modification (surface processing) of fiber bundles has been developed and tested for glass fibers. The system enables surface processing of single filaments and flat substrates as well. Surface processed glass fibers and their bundles were examined as reinforcements for glass fiber/polyester composite systems. Processing of fibers comprised a surface treatment using argon gas and a surface modification using hexamethyldisiloxane and vinyltriethoxysilane monomers. Interfacial and interlaminar shear strengths of plasma processed glass fiber/polyester systems were compared with those of untreated and commercially sized fibers.     

先进喷丸表面改性技术研究进展

综述了先进喷丸表面改性技术研究现状及应用,阐述了微粒子喷丸、激光喷丸、超声/高能喷丸、高压水射流喷丸的基本原理,与传统喷丸对比发现,微粒子喷丸可提高材料的耐磨性,激光喷丸可精确控制定位,超声/高能喷丸可实现材料表面纳米化,高压水射流喷丸可承受半柔性冲击并减少应力集中.此外,对各种喷丸技术综合分析并进行对比,认为超声喷丸、复合喷丸(高能-微粒喷丸,激光-机械喷丸)综合性能最佳,并展望了未来应重点开展的工作.     

Plasma transferred arc surface modification of a low carbon steel

The potential of Plasma Transferred Arc (PTA) hardfacing goes beyond the surface welding of superalloys. This work evaluated low carbon steel surface modification by PTA deposition of fine WCoC carbides, and mixtures of Fe powders and 5–35 wt% carbides. Characterization included visual inspection, optical and scanning electron microscopy, X-ray diffraction and microhardness profiles. PTA processing allowed for the dissolution of carbides confirmed by X-ray diffraction, leading to homogeneous microstructures. Microstructures varied from a Widmanstätten morphology to a typical dendritic solidification structure upon the WCoC content. Surface soundness depended on powder preparation and composition. Sound surfaces exhibiting hardness up to 700 Hv were obtained for the 35 wt% WCoC powder mixture.     

Boron modification of carbon fibres

An investigation is reported of the effect of boron modification on the mechanical properties of carbon fibres. It was found that the presence of boron in the furnace atmosphere does not affect the important structural features of the bulk of the fibres, that in many fibres the added boron is largely confined to the near-surface regions of the fibres, and that a large fraction of the boron is present as boron carbide. The largest improvements in strength were obtained when both carbon and boron were present in the furnace atmosphere.     

Plasma surface modification of polylactic acid to promote interaction with fibroblasts

In this work, medium pressure plasma treatment of polylactic acid (PLA) is investigated. PLA is a biocompatible aliphatic polymer, which can be used for bone fixation devices and tissue engineering scaffolds. Due to inadequate surface properties, cell adhesion and proliferation are far less than optimal and a surface modification is required for most biomedical applications. By using a dielectric barrier discharge (DBD) operating at medium pressure in different atmospheres, the surface properties of a PLA foil are modified. After plasma treatment, water contact angle measurements showed an increased hydrophilic character of the foil surface. X-ray photoelectron spectroscopy (XPS) revealed an increased oxygen content. Cell culture tests showed that plasma modification of PLA films increased the initial cell attachment both quantitatively and qualitatively. After 1 day, cells on plasma-treated PLA showed a superior cell morphology in comparison with unmodified PLA samples. However, after 7 days of culture, no significant differences were observed between untreated and plasma-modified PLA samples. While plasma treatment improves the initial cell attachment, it does not seem to influence cell proliferation. It has also been observed that the difference between the 3 discharge gases is negligible when looking at the improved cell-material interactions. From economical point of view, plasma treatments in air are thus the best choice.     

Effect of surface modification of Grewia optiva fibres on their physicochemical and thermal properties

This paper deals with the surface modification of Grewia optiva fibre through benzoylation and graft copolymerization process. Benzoylation of Grewia optiva fibre has been carried out on mercerized fibre with varying concentrations of benzoyl chloride solution. Graft copolymerization of acrylonitrile (AN) onto Grewia optiva fibre was carried out with ceric ammonium nitrate as the redox initiator in aqueous medium under the influence of microwave radiation. Raw, graft copolymerized and benzoylated fibres were subjected to evaluation of some of their properties like swelling behaviour, moisture absorbance and chemical resistance behaviour. It has been observed that 5% benzoyl chloride treated and graft copolymerized Grewia optiva show more resistance towards moisture, water and chemicals when compared with that of raw fibre. Further morphological, structural changes, thermal stability and crystallinity of raw, graft copolymerized, pretreated and benzoylated fibres have also been studied by SEM, FTIR, TGA and XRD techniques.     

Comparing the surface and internal structure of polypropylene fibres using advanced microscopy techniques

This paper highlights the importance of both surface and internal (bulk) structure of polypropylene (PP) melt extruded monofilament fibres and the dependence of structure on processing conditions. Gravity spun and as-spun fibres showed similar spherulitic surface structure but Wide Angle X-ray Scattering (WAXS) results indicated that the overall fibre crystallinity was contrasting for the two fibre types. From analysis of longitudinal and transverse fibre cross sections using Scanning Probe Microscopy (SPM) and Environmental Scanning Electron Microscopy (ESEM) it was found that gravity spun fibres showed a shish-kebab type structure in contrast to the macrofibrillar internal structure of the as-spun variant. In situ tensile testing gave powerful evidence to suggest that deformation in the necking region for the gravity spun fibres was due to the composite behaviour of the spherulitic surface and the internal shish-kebab structure.     

硅烷偶联剂对纳米ZnO的有机表面修饰研究

利用硅烷偶联荆(LM-N308)对纳米ZnO进行了有机表面改性.采用红外光谱(IR)、热分析(TG-DTA)、高分辨透射电镜(HRTEM)、润湿性实验等对表面改性前后的纳米ZnO进行了表征.红外光谱和高分辨透射电镜结果表明,在纳米ZnO表面有LM-N308的存在,并形成了有机包覆层.润湿性实验表明,经LM-N308表面改性的纳米ZnO由亲水性变成了疏水性.     

Surface modification of superdrawn polyoxymethylene fibres

The pull-out fracture of surface-modified superdrawn polyoxymethylene fibres embedded in rubber is discussed from a fractographical viewpoint. The morphologies of the pull-out fracture plane were very similar to those of the fracture surface in single lap-joint tests and the true pull-out stress coincided with the shear strength of a single lap-joint, indicating that the pull-out failure is strongly related to single lap-joint shear fracture.     

Nanomechanics of advanced polymer fibres

The micro/nano-structural evolution before and after tensile/compressive loading, fatigue and ultimately, failure has been studied by Raman (and IR) microspectroscopy for PBO, PET, PA66, PP, silk and hair using three probes: the low wavenumber collective modes at <150 cm⁻¹ as representatives of the crystalline/ordered and amorphous chains, the stretching and bending modes, as representative of the C–C/C–N polymeric backbone, and the localized vibrations (OH, NH) to probe the inter-macromolecule segment distance. The wavenumber and bandwidth distribution across fibre diameters reveal different types of skin/core heterogeneity. The in situ analysis at different strain/pressure levels shows that amorphous chains in the fibre accommodate the stress differently. The post mortem analysis shows that amorphous domains can be highly stressed during the failure and the remnant stress can be measured.     

Surface modification of superdrawn polyoxymethylene fibres

A new surface modification of superdrawn polyoxymethylene (POM) fibres, curing with resorcinol at mild temperatures, was developed to apply to rubber composites and the adhesion to the rubber matrix behaviour of modified fibres is discussed in terms of the interfacial miscibility between the fibre and adhesive surface layers. The modified fibre reached the maximum pull-out adhesion level in which a cohesive failure of the fibre occurs, resulting from the fact that the modified POM layer is spectroscopically close to the standard resorcinol-formaldehyde (RF) resin, thoroughly miscible and thermodynamically compatible with the resorcinol-formaldehyde-latex (RFL) adhesive.     

硬脂酸对纳米TiO2有机表面修饰方法的研究

报道了一种利用硬脂酸对纳米TiO2进行有机表面修饰的新方法,主要包括纳米TiO2水分散液的制备和把纳米TiO2粒子由水分散液中转移到溶有硬脂酸的甲苯溶液中两个过程.采用红外光谱(FT-IR)、X射线光电子能谱(XPS)、热分析(TG-DTA)、透射电镜(TEM)、粒度分布、紫外-可见光谱和分散性实验等对所得的样品进行了...     

Plasma modification of viscose textile

A study on plasma treatment of a textile is presented. Samples of pure viscose textile were exposed to RF oxygen, nitrogen or hydrogen plasma for 5 s. The gas pressure was 75 Pa and the RF power was 250 W. In all cases plasma treatment induced chemical changes in the samples' surface, which were determined by using high-resolution XPS (X-ray photoelectron spectrometer). Treatments in oxygen and nitrogen plasma increased the concentration of existing as well as formation of oxygen functional groups, while hydrogen plasma caused a substantial decrease of these groups. SEM (Scanning electron microscopy) analysis of the surface of the textile fibres was performed as well. The results showed that the fibres' surface treated in nitrogen plasma was similar to the untreated surface, while after treatment in hydrogen or oxygen plasma, the surface became rougher.