共查询到20条相似文献,搜索用时 15 毫秒
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M.W.G PonjéeM.A Reijme A.W Denier van der GonH.H Brongersma B.M.W Langeveld-Voss 《Polymer》2002,43(1):77-85
Surfaces of spin-coated and solution-cast poly(3-hexylthiophene) (P3HT) films are analysed by X-ray Photoelectron Spectroscopy and Low Energy Ion Scattering. Here, we use the P3HT-siloxane system with only 2% siloxane monomers in the bulk as a model system to study segregation and surface orientation of molecules in polymers. The surfaces are enriched in siloxane due to the intermolecular segregation of the siloxanes present in P3HT. The siloxane coverage fraction was found to depend on the preparation parameters such as spinspeed and solution-concentration, and ranges from 25 to 100%.The molecular orientation of segregated siloxanes on P3HT was found to resemble that on pure PDMS. Furthermore, siloxane molecules prefer specific sites on P3HT, such that sulphur atoms are screened from being at the outermost surface to lower the surface free energy. The results presented here demonstrate clearly the unique ability of LEIS to quantify the composition of the outermost atomic layer, and to obtain detailed information on the surface structure. 相似文献
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Markus Schweizer Simon Ruck Harald Riegel Volker Knoblauch 《Journal of Adhesion Science and Technology》2013,27(23):2581-2591
A promising joining technology for thermoset CFRP is adhesive bonding. However, the mechanical performance is influenced negatively by contaminants, like release agents, as well as an excess of matrix in the top layer. In order to generate most suitable surface qualities prior to the bonding process, carbon fibre reinforced plastics are treated with different – UV (355 nm) and IR (1064 nm) – lasers. The results are compared to commonly applied grinding surface preparation. The preliminary results on surface properties, e.g. energy and topography point towards high levels of free surface energy, as well as new originated surface structures. After the bonding process mechanical tests are subsequently carried out in Mode II, to characterize the final joint by its tensile shear strength. Finally, the individual fracture behaviour is examined in post mortem analysis. The results indicate that it is possible to increase the tensile shear strength of the joints to a maximum, which equals the interlaminar shear strength of the CFRP-laminate. Therefore, ultrashort pulsed IR-laser techniques show the best reproducibility and the highest tensile shear strength. In addition, IR-laser treatment is expected to have the highest potential for later applications. 相似文献
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In this article, effects of electrochemical oxidation and sizing treatment of PAN‐based carbon fibers (CFs) on the tensile properties, surface characteristics, and bonding to epoxy were investigated. As found, the electrochemical oxidation improves the tensile strength of single CF by 16.0%, due to weakening the surface stress concentration and smoothing the surface structure. Further sizing treatment shows a negligible effect on the tensile strength. Both oxidation and sizing treatments significantly improve the wettability and surface energies of CFs by introducing oxygen‐containing functional groups. Microbond test was conducted to characterize the interfacial shear strength (IFSS) between a single fiber and an epoxy droplet. The oxidation treatment increases IFSS slightly, which is due to the contradictory effects of the formation of chemical bonds between the resin and CFs, and the reduced mechanical interlocking. Further sizing treatment significantly enhances IFSS from 73.6 to 81.0 MPa, due to the formation of vast chemical bonds. Furthermore, the oxidation and sizing treatment can effectively reduce the degradation of IFSS to the hygrothermal ageing for the CF/epoxy system. POLYM. COMPOS., 37:2921–2932, 2016. © 2015 Society of Plastics Engineers 相似文献
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The exposure of preadsorbed oxygen to monomethylamine or the coadsorption of a 2:1 monomethylamine (CH3NH2)/dioxygen mixture at a Cu(211) surface at room temperature results in the formation of a surface species characterised by
C(1s) and N(1s) binding energies of 285.2 and 398.2 eV, respectively, with a calculated carbon to nitrogen ratio of 2:1. This
species, which we assign to a chemisorbed dimethylamine ((CH3)2NHx(a)), is the only adsorbed product of the reaction and its formation must involve the breaking of a carbon–nitrogen bond and
the intermolecular transfer of a methyl group.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
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This paper reviews existing literature related to the peel ply surface treatment of composite materials. A peel ply fabric is used as a removable layer in a composite lay-up and ripped off to modify the surface for adhesive bonding. A peel ply can affect the elemental composition of a surface and it is possible to distinguish between either a polyester or a polyamide peel ply treatment for a specific composite system and application. However, consistent and generalised relationships between the compositional modification or the surface energy and adhesive or resin adherence to treated surfaces are not probable. A compositional analysis and surface energy measurements are affected by the fractured matrix, peel ply fibre cavities and revealed reinforcements. Only a few recent studies have presented results for the regions of the matrix fracture and fibre cavities separately. Resin-impregnated peel plies, namely tear plies, offer additional tailorability for composite surface treatments, but related research is scarce. 相似文献
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以正十二碳硫醇为相对分子质量调节剂,参照传统调丁型氯丁橡胶(CR,牌号为244)的生产工艺,合成了硫醇调节型CR,考察了调节剂用量对CR相对分子质量的影响,通过傅里叶变换红外光谱和核磁共振氢谱表征了CR的微观结构,研究了CR的热性能和溶液稳定性,并与调丁型CR进行了比较。结果表明,随着硫醇用量的增加,CR的门尼黏度呈明显的下降趋势,达到相同调节效果时,硫醇用量仅为调节剂丁的1/4;硫醇调节型CR以反式-1,4-构型为主,以头-尾方式相连,且反式-1,4-结构含量略高于调丁型CR;硫醇调节型CR和调丁型CR的玻璃化转变温度基本相当,且随着温度的升高,出现晶区解晶现象;硫醇调节型CR与调丁型CR相比具有更优异的溶液黏度稳定性。 相似文献
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对玻璃基双层镍表面进行阳极活化以提高镍层之间的结合强度。阳极活化液组成和工艺条件为:NiCl2·6H2O 100 g/L,H3BO3 25 g/L,pH 4.0,温度45°C,阳极电流密度10~30 mA/cm2,时间5~15 min。研究了电流密度和处理时间对镍镀层表面形貌、孤岛结合力、表面粗糙度和界面结合强度的影响,探讨了双层镍表面粗糙度和界面结合强度的关系。结果表明,在30 mA/cm2下阳极活化10 min后,双层镍的界面结合强度为629.8 MPa,比盐酸活化试样高了近2倍。镍层表面粗糙度与界面结合强度之间有明显的对应关系,表面粗糙度越大,界面结合强度越高。采用阳极活化法可有效提高微机电系统微器件的可靠性。 相似文献
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This paper evaluates wet-chemical pre-treatments (alkaline etching, anodising) and a plasma treatment for structural bonding of titanium (Ti6Al4V). The main objective of this study is the comparison of the applicability of the plasma pre-treatment to wet-chemical treatments on titanium for structural bonding. In this context, an atmospheric pressure plasma device was used to deposit thin functional films from hexamethyldisiloxane (HMDSO) precursor on titanium.X-ray photoelectron spectroscopy (XPS) was employed to assess the chemical composition of the surface after different pre-treatments on the titanium substrate, while the morphology and the film thickness were investigated with scanning electron microscopy (SEM). The adhesion properties on titanium were evaluated by means of a wedge test in hot/wet conditions. After bonding tests the fracture surface and the failure loci were analysed.Using a long arc plasma generator and HMDSO precursor almost stoichiometric SiO2 coatings were obtained on the titanium substrate. These coatings exhibit good long-term durability and bond strength compared to an alkaline etching in the wedge test. The investigated anodising process leads to oxide layers revealing a highly porous nanostructure. In contrast to the alkaline etching, the plasma derived coatings and the oxide layer produced by the anodising process exhibit a higher micro, respectively nano roughness, and hence a better long-term durability. 相似文献
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J. Richard Hall Carolyn A. L. Westerdahl Andrew T. Devine Michael J. Bodnar 《应用聚合物科学杂志》1969,13(10):2085-2096
Polyethylene, polypropylene, poly(vinyl fluoride) (Tedlar), polystyrene, nylon 6, poly(ethylene terephthalate) (Mylar), polycarbonate, cellulose acetate butyrate, and a poly(oxymethylene) copolymer were treated with activated helium and with activated oxygen. Mechanical strengths of adhesive-bonded specimens prepared from treated and from untreated coupons were compared. Polyethylene (PE) and polypropylene (PP) showed the greatest increases in bond strength. Oxygen and helium were both effective with polyethylene, but polypropylene showed no improvement when treated with activated helium. The results with excited helium parallel the effects of ionizing radiation on these two polymers, as does the appearance of unsaturation bands in the infrared (965 cm?1 in PE, and 887 and 910 cm?1 in PP). Active nitrogen produced excellent bond strength with polyethylene but not with polypropylene. Of the remaining polymers examined, Tedlar, polystyrene, and nylon 6 showed the greatest improvement in bondability after treatment, and Mylar showed moderate improvement. Polycarbonate, cellulose acetate butyrate, and the poly(oxymethylene) copolymer gave approximately two-fold increases in lap-shear bond strength. In several cases, significant differences in response to time of treatment and type of excited gas were found. 相似文献
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通过X射线光电子能谱 (XPS)分析研究了碳热还原氮化法制备的AlN微粉的表面结合状态。结果表明 :AlN微粉的表面有明显的氧化层存在 ;AlN微粉表面结合状态为Al—O和Al—N复合型结合 ;杂质元素W主要是由球磨介质中的WC引入的 ,并以WO2 - 4形式分布于AlN微粉表面。 相似文献
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João Luiz Pozzobon Vinicius Felipe Wandscher Marilia Pivetta Rippe 《Journal of Adhesion Science and Technology》2013,27(15):1671-1682
It evaluated the effects of different zirconia surface treatments on the bond strength of a resin cement to Y-TZP (yttria-stabilized tetragonal zirconia) ceramics, as well as their phase-transformations. 75 blocks (5 mm × 5 mm × 4 mm) of Y-TZP were assigned into five groups (n = 15): (tribochemical silica coating - TBS) zirconia surface was abraded by silica coated alumina particles followed by silanization; (GLZ1) zirconia surface received the application of a thin layer of low-fusing porcelain glaze, followed by hydrofluoric acid (HF) etching for 1 min; (GLZ5) glaze application + HF etching by 5 min; (GLZ10) glaze application + HF etching by 10 min; (GLZ15) glaze application + HF etching by 15 min. After etching, all the specimens were washed, dried and silanized. Cylinders of composites (diameter: 3.25 mm; height: 3 mm) were cemented to the Y-TZP blocks using a resin cement. All the specimens were subjected to aging (10,000 thermal cycles and 90 days storage), tested under shear conditions, and finally analyzed by a stereomicroscope (failure analysis). In addition, we also performed topographical and phase transformation analyses of the treated zirconia surfaces. The TBS group presented the highest bond strength value (23.34 MPa). The glazed groups presented low bond values and high prevalences of pretest failures. X-ray diffraction analysis showed a phase transformation for the TBS group (13.14%); however, there was no clear phase change observed for the GLZ groups. From our results, we concluded that tribochemical silica coating is the main Y-TZP surface conditioning for resin bond improvements. 相似文献
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《Journal of Adhesion Science and Technology》2013,27(1):277-290
—We have shown that certain amine and amide curing agents for epoxy resins modify the surface properties of the fluoropolymer polyvinylidene fluoride (PVF2), thereby permitting the formation of strong adhesive joints. When PVF2 is exposed to these curing agents at the temperatures used in preparing adhesive joints (~70°C), discoloration (darkening) occurs with concomitant gelation. This suggests that there is dehydrofluorination followed by crosslinking. Infrared spectroscopy has been used to follow the course of these reactions. In effect, the curing agent serves a dual function. It reacts with the fluoropolymer both to modify the surface region and to crosslink the epoxy resin. 相似文献
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In our study, the effect of N-substituents on the surface free energy and hydrogen bonding network structure of polybenzoxazine has been studied systematically. The contact angle measurement results show the surface energies of the polybenzoxazines decrease with the increase of alkyl chain length, and are not affected by the steric factor of the tert-butyl group. However, the FTIR curve fitting results show that both the chain length and bulkiness of alkyl group have an effect on the hydrogen bonding network of the polybenzoxazines, and facilitate the formation of intermolecular hydrogen bonding during the progress of cure. This indicates that both alkyl group and the fraction of intermolecular hydrogen bonding have an effect on the surface energy of the polybenzoxazines. Additionally, the transformation mechanism of the intermolecular and intramolecular hydrogen bonding during the progress of cure is proposed for the first time. 相似文献
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为了实现对金属基陶瓷磨盘衬板高效、高质量的堆焊修复,选用自主研发的药芯焊丝在报废的陶瓷磨盘衬板上进行修复性研究。利用着色探伤、光学显微镜、扫描电镜等技术检测手段,对堆焊层与磨盘衬板的结合性、堆焊层应力释放裂纹的扩展情况进行了检测与表征,研究了堆焊层与磨盘衬板之间界面的结合情况。结果表明,自主研发的药芯焊丝所形成的堆焊层与磨盘衬板结合性良好,应力释放裂纹扩展细密均匀。经实践证明,在确保了堆焊层与母体结合性条件下,可对陶瓷磨盘衬板进行高质量的表面堆焊修复,改变目前陶瓷磨盘衬板只换不修的局面,对水泥行业降本增效有着积极的意义。 相似文献