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.     

Consideration of thermodynamic factors in the analysis of steel/polymer coupling agent/epoxy adhesion systems

—The work of adhesion, W_a, interfacial tension, g₁₂, and wettability envelopes for steel/ ethylene mercaptoester (EME) copolymer coupling agent/epoxy systems were calculated as a function of the EME mercaptoester concentration, using experimentally determined surface tension values from contact angle measurements. The thermodynamic parameters were compared with observed adhesion and corrosion protection results. Relationships between the EME/epoxy W_a values and dry adhesion strength, and the EME/steel W_a,L (in the presence of liquid) values and corrosion protection are discussed.     

The influence of zinc surface pretreatment on the adhesion of epoxy coating electrodeposited on hot-dip galvanized steel

The adhesion and electrochemical properties of epoxy coatings electrodeposited on hot-dip galvanized steel with and without passive films were investigated during exposure to 3% NaCl. The passive films were formed in hot air, in boiling water and by chromating. Adhesion was measured both by a standardized pull-off method and by swelling in N-methyl pyrrolidone. Pretreatment of hot-dip galvanized steel with passive film formed in hot air increases both dry and wet adhesion strength of the epoxy coating compared to pretreatment with passive film formed in boiling water and chromate coating. The overall increase of wet adhesion for this sample was maintained throughout the whole investigated time period. It was shown that the change in adhesion of epoxy coating on a chromate coating is smallest of all investigated samples, although the initial value of adhesion on this surface had the lowest value. The corrosion stability of coated Zn samples pretreated by different methods, was investigated by electrochemical impedance spectroscopy and in the initial time of exposure to NaCl the highest values of pore resistance were also obtained for the epoxy coating on Zn pretreated in hot air, whereas the epoxy coating on a HDG steel with a chromate coating showed the smallest change in electrochemical properties (pore resistance, coating capacitance, charge-transfer resistance) during prolonged exposure time.     

用丙烯酸锌改善EPDM与金属的粘合性能

采用均匀设计法对丙烯酸锌 [Zn(AA) 2 ]作为EPDM与金属的粘合助剂进行研究。试验结果表明 :在硫化过程中 ,Zn(AA) 2 与金属之间产生了具有提高粘合作用的化学键 ,明显提高了橡胶 金属的粘合力 ,用量为 10份左右时 ,在不涂粘合剂的情况下剥离强度达 10kN·m- 1 ;在硫化胶内部产生的离子交联键使其在提高粘合力的同时大大提高了EPDM硫化胶的物理性能     

Impact of adhesive ingredients on adhesion between rubber and brass-plated steel wire in tire

Proficiency on underlying mechanism of rubber-metal adhesion has been increased significantly in the last few decades. Researchers have investigated the effect of various ingredients, such as hexamethoxymethyl melamine, resorcinol, cobalt stearate, and silica, on rubber-metal interface. The role of each ingredient on rubber-metal interfacial adhesion is still a subject of scrutiny. In this article, a typical belt skim compound of truck radial tire is selected and the effect of each adhesive ingredient on adhesion strength is explored. Out of these ingredients, the effect of cobalt stearate is found noteworthy. It has improved adhesion strength by 12% (without aging) and by 11% (humid-aged), respectively, over control compound. For detailed understanding of the effect of cobalt stearate on adhesion, scanning electron microscopy and energy dispersive spectroscopy are utilized to ascertain the rubber coverage and distribution of elements. X-ray photoelectron spectroscopy results helped us to understand the impact of Cu_XS layer depth on rubber-metal adhesion. The depth profile of the Cu_XS layer was found to be one of the dominant factors of rubber-metal adhesion retention. Thus, this study has made an attempt to find the impact of different adhesive ingredients on the formation of Cu_XS layer depth at rubber-metal interface and establish a correlation with adhesion strength simultaneously.     

钢丝帘线不同粘合体系应用研究

研究有机钴盐品种和用量对载重子午线轮胎带束层胶料一镀铜钢丝帘线粘合力的影响。结果表明，加入硬脂酸钴、硼酰化钴和癸酸钴任何一种钴盐．胶料初始粘合力均较高，但硬脂酸钴胶料老化后的粘合性能较差，癸酸钴胶料的粘合性能略好，癸酸钴理想用量为0．58～0．81份。间／甲／白／钴粘合体系胶料老化前后的粘合性能均较好，粘合性能保持率较高，胶料的物理性能以及与钢丝的动态粘合性能均比生产配方胶料有所提高。     

纳米颗粒对环氧树脂胶粘剂／钢铁附着强度的影响

采用纳米Al2O3、纳米CaCO3、纳米SiO2三种纳米颗粒,机械混合对环氧树脂胶粘剂进行改性,并对纳米颗粒改性的环氧树脂胶粘试样进行了附着强度的检测。结果发现,通过改变纳米颗粒的种类和含量,环氧胶粘剂／钢铁基体之间的附着强度得到不同程度的提高,其中添加2％纳米Al2O3颗粒的环氧胶粘剂与钢铁基体的附着强度提高了4倍左右。通过断面形貌特征和不同基体粗糙度下对添加纳米颗粒环氧胶与钢铁基体之间附着强度的检测,对此现象产生的原因进行了分析和讨论。     

Aging effect in the adhesion of a PC/CPVC arrangement for application in thermo-solar collectors

This work studies the aging of materials in a polycarbonate/chlorinated polyvinyl chloride (PC/CPVC) arrangement, used in a flat plate thermo-solar collector. Typically, PC is used as an absorbing surface and CPVC in entrance and exit heads of the flow, which in this case is water. In this study, two types of methacrylate adhesives were used to bond both plastics, denominated MP and SK. The experiment comprised a study of adhesion behavior between these polymers and the adhesives, in contact with distilled water at different temperatures and different time intervals, simulating the corresponding operating conditions of a thermo-solar collector. Results showed that the SK adhesive did not fail under these conditions, while the MP adhesive underwent evident aging and adhesive failure. In addition, the PC presented a reduction in its mechanical strength when it was subjected to higher temperatures and periods of hygrothermal exposure, probably due to physicochemical deterioration caused by hydrolysis.     

The effect of photooxidation aging on the cohesion and interfacial adhesion behavior of epoxy asphalt with a composite acidic curing system based on molecular simulation

This paper investigated the cross-linking network structure of epoxy asphalt (EA) with the different ratio of composite curing agents, and further determined the effect of photooxidation aging on the tensile and interfacial adhesion behavior of EA with different cross-linking network structures through molecular simulation. Based on the molecular models of EA and the interface model between EA and aggregate, the crosslinking network structural characteristics and tensile mechanical behavior were determined. The interfacial adhesion behavior and the mechanization were further studied. The results indicate that 20-EA and 6-EA have an epoxy resin cross-linked network with uniform pore structure and phase distribution. 2-EA showed a denser cross-linking network and uneven aggregation phenomenon. Photooxidative aging alleviated the aggregation phenomenon. A dense cross-linking network improved the tensile strength and the ability of tensile performance to resist photooxidation aging. The interface of EA-quartz exhibited higher adhesion strength than EA-calcite due to the closer distance and stronger nonbonding interactions between EA and quartz. The low anhydride content and photooxidation aging made EA approach to the aggregate interface, increasing nonbonding interaction and interfacial adhesion strength. In addition, quartz aggregates were more suitable for application in EA mixtures due to the higher interfacial adhesion strength and lower water sensitivity.     

仿生材料多巴胺对橡胶/钢丝帘线黏合性能的影响

选用子午线轮胎胎体胶料配方作为基本配方,以钢丝帘线作为骨架材料,采用自行研发的橡胶与钢丝帘线动态黏合性能的测试方法,考察了多巴胺及传统黏合体系对橡胶/钢丝帘线动态黏合性能的影响,并探讨了多巴胺替代间苯二酚作为无毒环境友好型黏合剂的可行性。结果发现,钴盐黏合体系赋予了橡胶与钢丝帘线较好的动态黏合,多巴胺体系赋予了较好的静态黏合,间甲白体系居中,3种黏合体系并用可赋予最好的动、静态黏合性能。橡胶/钢丝帘线的动、静态黏合力均随着多巴胺用量的增加而增大,但在拉伸疲劳后出现下降。     

A surface analytical study of the formation and adhesion of chromium films on alumina

Chromium-alumina bonding was characterized by using surface analysis techniques. The metal-ceramic interface was produced by vapour deposition of the metal at room temperature in an ultra-high vacuum chamber equipped with AES (Auger electron spectroscopy), EELS (electron energy loss spectroscopy), and XPS (X-ray photoelectron spectroscopy) facilities. Two kinds of alumina surface were used as the support for Cr condensation: a stoichiometric (1×1) α-Al₂O₃ surface (called the perfect surface or class a) and an oxygen-deficient surface giving rise to LEED patterns (called the reduced surface or class b). It is shown that on perfect surfaces the Cr film grows layer by layer but on reduced surfaces a three-dimensional (3D) growth process is observed. These results are explained by a strong chemical interaction between Cr and the class a surface, and by 3D nucleation on defect sites on the class b surface. After ageing for a few days under vacuum, the thick Cr film deposited on the reduced surface delaminates. This behaviour can be interpreted as competition between Cr atoms and Al ions to form an interfacial oxide layer.     

Photocurable epoxy/cubic silsesquioxane hybrid materials for polythiourethane: Failure mechanism of adhesion under weathering

A new inorganic–organic hybrid coating containing epoxy‐functionalized cubic silsesquioxane (CSSQ) has been developed, which can be polymerized cationically by UV radiation. This solvent‐free solution can be used as hybrid coating for polythiourethane (PTU) substrate. The surface properties of the coating film were determined by adhesion and scratch resistance. The excellent adhesion of coating films on the substrate was observed at the initial stage before weathering, but deteriorated after exposure to the sunshine. The low viscosity of hybrid coating solution (～ 15 mPa s) leads to fast curing and the formation of hybrid coating film during the photopolymerization reaction. The adhesion failure was evaluated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS) analyses. AFM images showed that the surface is smooth at the initial stage, but a texture surface was developed after weathering. The shrinkage of the hybrid film due to the increase in crosslinking density by postpolymerization would affect the surface roughness after weathering. XPS analysis indicated that the adhesion failure occurred by photodegradation of the PTU substrate during weathering. The weathering resistance was significantly improved by adding UV absorbers, which protected the polymer substrate from the photodegradation. The advantages of the hybrid coating include fast cure speed, solvent‐free formulation, and improved surface properties of the coating film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigations on gas-phase reactions of ethane under SOFC conditions: An experimental and modeling study

Experiments using a model gas mixture which is chosen to represent hydrocarbon fuel from hydrothermal gasification of biomass were carried out under gas-phase conditions similar to those expected in the anode channel of a solid-oxide fuel cell (SOFC). Ethane conversion and product formation were evaluated from the measurements at various temperatures ranging from 610 °C to 860 °C and at a total pressure of 1.2 bar. The employed reactor was simulated using a plug-flow model coupled to a detailed gas-phase reaction mechanism. The measured temperature profile along the reactor was imported in the calculation routine. A satisfying agreement in both ethane conversion and product composition was reached between the model predictions and the experimental data. In order to determine which reactions were responsible for much of the observed kinetics a sensitivity analysis based on the rate of production (ROP) principle was performed. The results from the sensitivity analysis show that there are only six elementary reactions whose rates significantly affect the consumption or formation of the four species of interest, i.e. H₂, CH₄, C₂H₄ and C₂H₆.     

云南某富银锌精矿锌银浮选分离实验研究

云南某富银锌精矿中银主要以类质同象形式存在于白铅矿中,本工作以该矿样为研究对象,根据其性质,采用抑铅浮锌的工艺流程进行浮选,考察了磨矿细度、抑制剂、活化剂及捕收剂等因素对浮选分离指标的影响。结果表明,–19+10 μm粒级中银含量最高。在磨矿细度–74 μm占90%,硅酸钠用量为2000 g/t,硫酸铜用量为200 g/t,丁基黄药用量为300 g/t,松醇油用量为30 g/t的条件下,1次粗选、1次精选、1次扫选,中矿顺序返回的全流程闭路实验,可获得含锌61.08%,回收率95.89%的锌精矿和含银1548.32 g/t,回收率为71.17%的银精矿,实现了锌银的浮选分离及伴生银的高效富集。     

Modification of a nitrile-phenolic bonding agent by addition of an interfacial agent: effect on the practical adhesion between nitrile rubber and metal

—The mechanism of vulcanization bonding of a nitrile rubber (NBR) elastomer to metal with a single-coat nitrile-phenolic bonding agent is discussed. A nitrile-phenolic bonding agent consisting of NBR, phenol formaldehyde (PF) resin, and vulcanizing agents was modified with an interfacial agent (p-cresol formaldehyde resin) and the effect of interfacial agent addition on the practical adhesion between metal and the NBR elastomer after vulcanization was investigated. The adhesion strength was measured in terms of the metal-to-NBR elastomer peel strength using the bonding agent. The addition of p-cresol formaldehyde (PCF) resin to the bonding agent with a proportionate reduction of PF resin initially improved the peel strength; a maximum was reached at about 20% PCF content and then decreased with a further increase in the PCF content. The improvement in peel strength produced by the addition of PCF resin is attributed to the increased chemical bonding between NBR and the phenolic resin. The drop in peel strength above 20% PCF content is explained by the increased diffusion of the bonding agent into the NBR elastomer, away from the bond line, leading to a starved glue line. The mechanism for the optimum performance at about 20% PCF resin content is believed to be due to the balance of diffusion and chemical crosslinking.     

Effects of polyacrylic acid primers on adhesion and durability of FPL-etched aluminum/polyurethane systems

It has been determined that when a polyacrylic acid [p(AA)] macromolecule primer is used in polyurethane (PU)/p(AA)/FPL-etched aluminum joint systems, it interacts preferentially both with the hydrated Al₂O₃ or aluminum hydroxide adherend surface through the formation of hydrogen bonds and with the isocyanate groups in the PU adhesive to yield polymer-to-polymer chemical bonding. This chemical crosslinking between the hydrated adherend and the polymeric adhesive acts significantly to promote interfacial adhesive bonds. It appears that a near monolayer of p(AA) is enough to occupy all the available functional groups at the PU and aluminum surface sites. This arrangement plays a key role in improving the adhesion durability of the joint system upon exposure to a hot NaOH solution. It was also determined that the presence of excessive carboxylic acid groups resulting from the use of a thick p(AA) layer caused gel-formation-induced adhesion failures; namely, the locus of failure of the joint after exposure was clearly identified to be cohesive failure in the primer.     

Improved interfacial adhesion with the help of functional polyhedral oligomeric silsesquioxanes in silicone rubber/rayon fiber composites: Physical,mechanical, thermal,and morphological properties

The aim of this article is to improve the interfacial adhesion between silicone rubber (SR) and Rayon fiber by the help of functional hybrid POSS nanoparticles. Two POSS types were compared, octavinyl-POSS (O-POSS) and methacryl-POSS (M-POSS), having reactive  CC double bonds that can impart in peroxide crosslinking. O-POSS is nonpolar, whereas M-POSS is polar and is able to make H-bond with Rayon fibers. POSS type and their concentrations were examined as the experimental parameters. H-adhesion tests indicated that both POSS types enhanced the adhesion of SR composites to Rayon fibers compared with control recipe. Specifically, slightly higher values were obtained with the use of M-POSS. It was observed that both O-POSS and M-POSS slowed down the curing rate but increased the degree of crosslinking. The cure extent of O-POSS containing composites was found to be higher than that of M-POSS containing ones. Thermal gravimetric analyses revealed that thermal stability of SR composites was significantly improved by the addition of POSS particles. Higher char yield and degradation temperatures were obtained with O-POSS at higher loadings with respect to M-POSS. The POSS distribution at lower loading levels was found to be homogenous for both POSS types as observed from scanning electron microscope and transmission electron microscope.     

UP/PU嵌段共聚树脂/玻璃纤维界面粘结性的研究

合成了一种异氰酸酯嵌段共聚改性不饱和聚酯树脂(UP/PU),并以玻纤增强制备了复合材料(GFRP)。通过接触角、拉伸性能、弯曲性能测定和扫描电镜观察研究了UP/PU GFRP界面的粘结性能。结果表明:UP/PU树脂与玻璃表面的接触角为20°,对玻璃表面的润湿性较通用邻苯型UP好;GFRP拉伸强度1 050 MPa,弯曲强度1 220 MPa,较通用邻苯型UP的GFRP分别提高了145%和78%,说明UP/PU与玻纤的界面粘结性能较好。     

Numerical study of the effect of carbon fiber/epoxy resin adhesive thickness on the creep behaviour of carbon steel plate joints

Nowadays, the use of adhesive and adhesively bonded joints have been considerably appreciated in the industry due to the dramatic reduction in bonding strength, reduced stress concentration, rust prevention, uniform bonding of the bonding surface and a significant reduction in costs compared to other types of permanent joints such as welding. In this study, the effect of adhesive thickness on creep behaviour of a single lap adhesive joint with the aid of Abaqus FEM software is investigated. It should be noted that the two-layer and two-dimensional models are considered, in which their adhesive layer is made of a reinforced epoxy resin with 0.5% carbon fiber and the adherend layers are made of carbon steel plates, which is affected by tensile forces. Since the main purpose of this paper is to study the effect of adhesive thickness on the adhesive joints behaviour, the effects of the distribution of shear stress, effective stress and creep strain were studied in different thicknesses of the adhesive layer. The results show that by increasing the thickness, the stress and the creep strain decrease, and over time, the stress decreases and the creep behaviour of adhesives increases.     

Effects of a new 4-acryloxyethyltrimellitic acid in a visible light-cured dental adhesive on adhesion and polymerization reactivity

A new adhesive-promoting monomer, 4-acryloxyethyltrimellitic acid (4-AET), was synthesized. The effects on the adhesion to bovine dentin and the polymerization reactivity [the inclusion varying from 0 to 10 wt % 4-AET of the experimental light-cured dental bonding resins (adhesive), wherein the adhesives were aged artificially at 50°C over 2 weeks] were investigated, using tensile and shear bond testing, a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM). Tensile and shear bond strengths to ground dentin were not significantly decreased in 4-AET content over 2 weeks of aging, and the optimum concentration of 4-AET was found to be 5 wt %. The correlation between the tensile and shear bond strengths to the dentin was highly positive (r = 0.8517–0.9329) during the 2 weeks. The maximum temperature (T_max) of the polymerization in DSC was affected by the 4-AET content in the positive correlation. The correlation between the T_max and the bond strength to dentin was highly positive (r = 0.8995–0.9644). The SEM study showed that the bonding resin appeared to adhere strongly to ground dentin without the formation of resin-tags in the dentinal tubules. It was suggested that the bonding strength was attributable to the degree of penetration of the 4-AET/HEMA primer into the dentin and the polymerization reactivity of the bonding resin comprising 4-AET. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1057–1069, 1998