Adhesion properties and fracture mechanism of plasma sprayed NiCrAl/Al2O3–13wt.%TiO2 coatings by post annealing

Plasma-sprayed NiCrAl/Al₂O₃–13wt.%TiO₂ coatings (AT13) deposited on mild steel substrate were annealed with varying temperatures in air. The adhesion of the coating was evaluated by tensile adhesive strength test. The microstructure and the fracture mechanism were studied using optical microscopy, X-ray diffraction, and scanning electron spectroscopy/energy dispersive spectroscopy. It was found that the tensile bond strength of the coatings increased with increasing of annealing temperature at first and then decreased with increasing of annealing temperature further. The as-sprayed coating fractured at the interfaces of substrate/bond layer and bond layer/ceramic coating with a brittle–ductile mixed fracture. The measured strength expressed the adhesive strength and internal adhesive strength of the coating. The failure of the coating annealed at 300, 400, and 500 °C took place at the interface of substrate/bond layer and had a mixed fracture surface of transgranular cleavage fracture and localized ductile fracture. The strength obtained is the adhesive strength between the coating and the steel substrate. The coating annealed at 400 °C had a maximum strength of 42.9 MPa. When the temperature is above 600 °C, the bonding strength would be damaged. Therefore, there is a proper annealing temperature which can significantly improve the bond strength of the coating.     

Effect of pulsed laser irradiation on the SiC surface

The effect of a pulsed laser irradiation (Nd:YVO₄, 1064 nm) in air on the surface morphology and chemical composition of silicon carbide and on the adhesion with an epoxy adhesive was investigated. Scanning and transmission electron microscopies, atomic force microscopy, and X‐ray photoelectron spectroscopy revealed that the laser treatment reduced the contamination level of the surface and induced the formation of a silica‐based nanostructured columnar layer on the SiC surface. The mechanism for the formation of five different microstructural regions is described in this paper. In addition, the formation of a 5‐10‐nm‐thick graphite layer between the oxide layer and SiC was observed. The joining test with Hysol^® EA9321 showed that the nanostructured columnar silica layer was completely infiltrated by the adhesive, thus leading to a significant increase in the joined specific area and a mechanical interlocking at the adhesive/substrate interface. Nevertheless, the apparent shear strength of the joined SiC samples slightly decreased after the laser processing of the surfaces from about 42 MPa for lapped SiC to about 35 MPa for laser‐nanostructured SiC. The formation of the graphite layer was found to be responsible of the poor adhesion properties of the SiC surfaces modified by the laser radiation.     

Dry adhesion study of polyester/melamine clear coats on galvanized steel

The dry adhesion strength of polyester/melamine clear coats varying in their branching degrees were applied on galvanized steel panels and investigated by pull-off and T-bend testing. It was found that pull-off tensile adhesion is mainly dominated by the type of coating and less influenced by the pretreatment of the substrate. In contrast, the critical T-bend strain is mainly affected by the surface treatment of the galvanized layer with higher stiffness but lower ductility compared to the clear coat. Pull-off tensile strength at room temperature is correlating with the glass transition temperature T_g and a strong viscoelastic contribution is ascribed to the work of adhesion. Samples with adhesive as well as cohesive failure modes were further investigated by X-ray photoelectron spectroscopy (XPS) to determine the interfacial chemistry. Angle-resolved XPS data suggest that the nitrogen from the melamine crosslinker plays a decisive role for the adhesion of the coatings. Regarding the melamine distribution a micro- and a nanostructural effect has to be considered: while maximum melamine concentrations over coating depth are usually found in the bulk region of these clear coats, this work proposes that the remaining melamine at the interface segregates towards the metallic substrate.     

SEM/EDX studies of the influence of a cobalt adhesion promoter on the interface between rubber skim compounds and tire steel cord

The failed interfaces between natural rubber skim compounds and tire steel cord used as tire cord adhesion test (TCAT) specimens have been studied by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis in order to understand the influence of cobalt boroacylate in the rubber compound as an adhesion promoter. SEM studies indicated a mixture of cohesive failure in the rubber and interfacial failure between the rubber and the brass coating. Cobalt boroacylate leads to more cohesive failure of the rubber (about 88% of the cord area covered by the rubber compared with 73% by the control), due to its degradative effects on rubber. EDX analysis of the failed cord and rubber surfaces at various points gave the concentrations of copper, zinc, cobalt, iron, silicon, sulfur, oxygen, and carbon. Assuming van Ooij's model of interfacial sulfide film formation over the brass (Cu/Zn) layer and analyzing the EDX results, it is clear that the failure occurs at the Cu/Zn and Cu_xS/ZnS sub-layers.     

钴盐用量对橡胶与钢丝帘线粘合性能的影响

对硼酰化钴ＭＣ２３（钴质量分数为２３％）用量（０６～１６份）对橡胶与钢丝帘线粘合性能的影响进行研究。采用的基本配方为：ＮＲ１０００；炭黑Ｎ３２６６２０；芳烃油８０；氧化锌９０；硬脂酸０５；防老剂４０２０２０；不溶性硫黄ＩＳ７０２０６０；促进剂ＤＺ１０；粘合剂ＲＳ３５；粘合剂Ａ２３；沉淀法白炭黑５０。结果表明，随着钴盐用量的增大，在未老化、热空气老化及盐水老化条件下，胶料与钢丝的粘合强度有所提高；在湿热老化条件下，粘合强度由于热量和湿气的交互作用而发生较大幅度的下降，但钴盐用量在１０份时粘合强度的下降为最小。综合胶料初始和老化后的应力应变性能和粘合强度，以１０份钴盐用量为最佳。     

Interfacial adhesion between polymer separation layer and ceramic support for composite membrane

An in situ characterization method for mechanical and adhesive properties of organic/ceramic composite membranes is built on the basis of nanoindentation technique in this work. The polydimethylsiloxane (PDMS) was used as the separation layer with the support of porous ZrO₂/Al₂O₃ ceramic tubes. The effects of roughness of the ceramic support and the viscosity of PDMS solution on the mechanical properties of the PDMS separation layer and the interfacial adhesion at the interface were investigated in detail. It was found that when the roughness of the ceramic support increased and the viscosity of PDMS solution decreased, the interfacial adhesion strength of PDMS/ceramic composite membrane increased, but these two variables had little effect on the mechanical properties of the PDMS separation layer. Our results indicate that the mechanical interlocking dominates the adhesion between the PDMS separation layer and the porous ceramic support. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Oxidation of the copper alloy with pure copper plating

The oxidation failure of a copper alloy lead frame with/without a copper plating layer was investigated. The oxidation rate and adhesion strength of oxide films on copper alloy substrates were studied by measuring the thickness and by carrying out peel tests. The adhesion strength of the oxide film was mainly influenced by the composition but not the thickness of the oxide film. The highest adhesion strength was obtained when the oxide film was composed mainly of Cu₂O. When the thickness of the copper preplated layer was over 0.165?μm, the Cu atoms of the preplated copper were available for oxidation. Thus the oxidation process was within the copper preplated layer, and the main product of the oxidation was Cu₂O. It was found that the large column grain of the oxide film on the copper alloy with a copper plated layer, favored the diffusion of copper or oxygen atoms that led to the formation of Cu₂O, and lead to higher adhesion strength. This indicated that the oxidation resistance of a copper alloy lead frame can be effectively improved by electroplating copper.     

Study of Cu–Zn–Co ternary alloy-coated steel cord in cobalt-free skim compound

In this study, it is shown that the rate of bond degradation due to ageing in hot & humid conditions can be significantly reduced by the use of a Cu–Zn–Co ternary alloy coating, compared to current compounds and normal brass-coated steel cord. To better understand the adhesion mechanism, X-ray photoelectron spectroscopy is used to investigate the adhesion interface upon hot and humid ageing. In addition, the effect of removal of cobalt salts from compound on static and dynamic rubber compound properties is studied: it is found that this leads to improved heat ageing resistance, slower crack growth rate and less hysteresis. Hence, the new Cu–Zn–Co ternary alloy coating for steel cord allows cobalt salts to be removed from tires, which makes tires more durable and eco-friendly.     

Effect of laminating parameters on the adhesion property of flexible copper clad laminate with adhesive layer

In this study, the effect of two laminating parameters, laminating pressure and holding time, on the adhesion strength of flexible copper clad laminate (FCCL) with an epoxy-type adhesive layer was evaluated. The changes in the adhesion property, fracture surface, morphology, and chemical bonding state were characterized by 90° peel test, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that the adhesion strength of the FCCL was decreased as the laminating pressure was increased beyond the suitable level. Laminating pressure exerted the greatest influence over the FCCL adhesion strength. On the other hand, the holding time did not significantly affect the peel strength of the FCCL. The fracture of FCCL occurred at the interface between the rolled Cu and the adhesive layer. In addition, the FCCL with high adhesion strength was stable with the variation of adhesion strength after temperature and humidity test.     

Polymer-Solid Interface Connectivity and Adhesion: Design of a Bio-Based Pressure Sensitive Adhesive

Adhesion at polymer-solid interfaces was explored for a new bio-based pressure sensitive adhesive (PSA) in terms of sticker groups, φ_X, on the polymer phase, receptor groups, φ_Y, on the solid surface, and the bond strength of the sticker-receptor X-Y acid-base interaction, χ. The polymer-solid interface restructuring models of Gong and Lee et al. were extended with new percolation models of entanglements and interface strength to determine the optimal sticker group concentration, φ?_X. For the general case where φ_Y and χ are constant, it is predicted that when φ_X < φ?_X, that the critical peel energy behaves as G_1c ～ φ_X/φ?_X and the locus of failure is adhesive between the polymer and the solid. However, when φ_X > φ?_X, failure occurs cohesively in a polymer-polymer interface adjacent to the solid and the strength decreases as G_1c ～ φ?_X/φ_X. The switch from adhesive to cohesive failure can be understood in terms of the changes in the chain conformations of the adhered chains and their decreasing interpenetration, X_i, with the bulk chains, via X_i ～ 1/r, where r = χφ_Xφ_Y. The optimal value of φ_X which maximizes the adhesion and determines the mode of failure is given by φ?_X ≈ 0.129/C_∝, and for typical values of the characteristic ratio C_∝ in the range 7–20, φ?_X ≈ 1% mole fraction, corresponding to about 2 sticker groups per entanglement molecular weight, M_e. This result was verified for a bio-based PSA synthesized from an acrylated high oleic fatty acid, which was copolymerized with maleic anhydride as the sticker group. The observed behavior is counterintuitive to the current wisdom for the effect of acid-based interactions on adhesion, where the strength is expected to increase with the number of X-Y contacts. The surprisingly low value of φ?_X ≈ 1% sticker groups which maximizes the adhesion strength can now be readily calculated using the percolation model of entanglements and fracture.     

Synthesis of cobalt complexes and their evaluation as an adhesion promoter in a rubber–steel wire system

Cobalt adhesion promoters are considered as one of the most important ingredients in the tyre industry for adhesion between the rubber compound and the brass plated steel cord for manufacturing of steel-belted radial tyres. Most of the commercially available cobalt compounds are either higher fatty acid salts, or cobaltchelate complexes, e.g., cobalt octate, naphthenate, stearate and cobalt-boron complexes. Among all the available cobalt salts, cobalt-boron complexes are the most popular ones and bond well. Considering the availability, economics and performance of the different cobalt salts, an attempt has been made in this study to synthesise different cobalt-chelate complexes and to make a comparative evaluation. In some of the cases the cobalt complexes developed showed better adhesion properties as compared to the control compound.     

Effect of Anion in Cobalt Promoters on the Adhesion between Steel Cord and Rubber Compound

There is widespread use of two main groups of adhesion promoters, the SRH-system and an organic cobalt salt. They are used either jointly or individually in the rubber compound for promotion and maintenance of good adhesion of rubber to brass-coated steel cord in radial tyres.

This paper describes the influence of anions associated with cobalt promoters on the adhesion energy and the pull-out force between brass-coated steel cord and rubber and their relationship to other relevant physical properties, under the influence of various environments which simulate tyre service conditions.

It is observed that incorporation of a cobalt promoter greatly enhances the adhesion energy and influences the Young's modulus and crosslink density of the rubber compound in a similar fashion. The study establishes the supremacy of boroacylate among the anions considering its overall good performance and the protection offered against various hostile environments. However, the benefits of the cobalt promoter is not realised with stearate ion. The results are explained on the basis of chemical stability of the promoter and the properties of the interfacial film and the compounds.     

钴盐对钢丝帘线与橡胶粘合性能的影响

对环烷酸钴，硼酰化钴，新癸酸钴等钴盐粘合增进剂对高和低铜质量分数钢丝帘线与橡胶粘合性能的影响进行了研究。结果表明，胶料中加入钴盐能够提高强伸性能和与钢丝帘线的初始粘合唱 力及耐盐水老化能力。     

Changes in the adhesion strength between copper thin films and polyimide substrates after heat treatment

The adhesion strength between a copper (Cu) thin film and a polyimide [pyromellitic dianhydride-oxydianiline (PMDA-ODA)] substrate is reduced by heat treatment at 150°C in air. In this work, we determined the changes in adhesion strength between Cu films and polyimide substrates using Auger electron spectroscopy (AES), attenuated total reflection Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The analysis showed that the weak boundary layer (WBL) shifted towards the Cu interface as the heat treatment time was increased. To confirm this shift, we looked at two other polyimide substrates: biphenyl dianhydride-p-phenylene diamine (BPDA-PDA) and biphenyl dianhydride-oxydianiline (BPDA-ODA). Comparing the adhesion strength for the Cu thin film, the adhesion strength was high for the Cu/PMDA-ODA and Cu/BPDA-ODA laminates, but very low for the Cu/BPDA-PDA laminate. One of the possible reasons for this behavior could be that the ether moiety between the two benzene rings in ODA is related to the adhesion between a Cu film and an 0₂-plasma-treated polyimide (PI) substrate. The relationship between the adhesion strength and chemical bonding states is also discussed. We conclude that a Cu thin film sputtered onto a PI substrate is apt to peel at the oxidized interface, due to the heat treatment.     

高初粘力EPDM/金属界面胶粘剂的研究

在三元乙丙橡胶胶粘剂AE-2基础上,探索了提高EPDM/金属界面胶粘剂初粘力的途径,考察了增粘树脂HX,HY-209,GMA,TX和R11等对胶粘剂初粘力的影响,重点研究了增粘树脂HX用量对EPDM/金属界面粘接性能的影响,确定了高初粘力EPDM/金属界面胶粘剂AE-9配方组成.结果表明,加入增粘树脂HX后EPDM/金...     

载重斜交轮胎胎圈钢丝包胶配方优化

对载重斜交轮胎胎圈钢丝包胶配方进行优化。试验结果表明:在胎圈钢丝包胶中加入粘合剂RH和硼酰化钴,增大补强填充剂和芳烃油的用量,并对配方进行适当调整,胶料强度虽有所降低,但与胎圈钢丝的粘合性能明显提高,成品轮胎胎圈质量改善,生产成本降低。     

Weak boundary layers on vulcanized styrene–butadiene rubber treated with sulfuric acid

A synthetic vulcanized styrene-butadiene rubber (R2) was used in this study. The presence of paraffin wax and zinc stearate in the rubber composition prevented the adhesion of R2 rubber to solvent-based polyester-urethane adhesive. To increase the adhesion properties of R2 rubber, a surface treatment with sulfuric acid (cyclization) was applied, and the length of the immersion in sulfuric acid and the time between the immersion time and the neutralization were varied. The treated R2 rubber surfaces were characterized using ATR-IR spectroscopy, contact angle measurements (water, ethanediol), and scanning electron microscopy (SEM). The mechanical properties of the treated rubber were obtained from stress-strain experiments. The joint strength was obtained from the T-peel test on treated R2 rubber/polyurethane adhesive joints. Due to the penetration of the sulfuric acid into the R2 rubber bulk, the mechanical properties decreased. The treatment with sulfuric acid produced several chemical modifications on the rubber surface: sulfonation of the butadiene and the creation of C C and C O bonds. Furthermore, the surface treatment of the R2 rubber with sulfuric acid removes paraffin wax from the rubber surface, which had a beneficial effect on adhesion to the polyurethane adhesive. To remove the wax layer, the surface was wiped with petroleum ether solvent after treating the R2 rubber with sulfuric acid. However, in some experiments a progressive migration of wax from the R2 rubber bulk to the surface with time happened. The migration of wax was prevented by increasing the immersion time in H₂SO₄ by more than 5 min.     

对羟基苯甲酸钴钻(镍)对天然橡胶与黄铜粘合的影晌

研究了对羟基苯甲酸钴和对羟基苯甲酸镍对天然橡胶与黄铜粘合的影响。实验结果表明，天然橡胶胶料中加入适量的对羟基苯甲酸钴（镍），可提高胶料的粘合性能，静态粘合强度最高可提高１倍。镍盐的效果尤为显著，它不仅使胶料具有较高的静态粘合强度，而且还具有良好的动态粘合和抗湿热老化性能。     

Surface modification of aromatic polyamide film by plasma graft copolymerization of glycidylmethacrylate for epoxy adhesion

The graft copolymerization of glycidyl methacrylate, GMA, onto poly(p-phenylene terephthalamide), PPTA, film surfaces was investigated to improve adhesion between the PPTA film and epoxy adhesives. The graft copolymerization of GMA was carried out in two steps; a peroxide formation by a combination of argon plasma irradiation and air exposure, and the polymerization reactions of GMA. XPS analyses showed the graft copolymerization of GMA on the PPTA film surface, and only 31–40% of the PPTA film surface was covered with the GMA graft polymers. The graft copolymerization of GMA improved the adhesion between the PPTA film and the epoxy adhesive. The adhesion strength was improved 2.7 times by the graft copolymerization. The failure from the adhesive joint occurred in the epoxy adhesive layer rather than at the interface between the PPTA film and the epoxy adhesive layer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1179–1185, 1998     

Improvement in the adhesion of polyimide/epoxy joints using various curing agents

An improvement in the adhesion strength of polyimide/epoxy joints was obtained by (1) introducing a functional group on the polyimide surface, (2) improving the mechanical properties of the epoxy adhesive, (3) increasing the curing temperature, and (4) using polyamic acid as an adhesion‐promoting layer. The functional group on polyimide was introduced via treatment with aqueous KOH. An adhesion‐promoting layer was formed by spin coating polyamic acid onto a modified polyimide surface. The maximum adhesion strength of the polyimide/epoxy joint was obtained using polyamic acid as both the adhesion‐promoting layer and as the curing agent. The surface energy of the modified polyimide was examined using contact angle measurements and Fourier transform infrared spectroscopy, and the peel strength was determined by the T‐peel method. The peeled surfaces were analyzed using scanning electron microscopy and X‐ray photoelectron spectroscopy.© 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 812–820, 2002