Epoxysilane as adhesion promoter in duplex system

Coatings are one of the most used protection methods for metals. Metallic coatings, such as zinc and its alloys, are used to protect steel in mild corrosive environments. In aggressive environments, on the other hand, organic coatings must be employed in the so-called duplex systems. However, the galvanized steel/organic coating adhesion is a problem and many attempts had been done to solve it with the incorporation of a chromate-based or phosphate-based interlayer. Nowadays, the use of these compounds is questioned due to their environmental impact and new adhesion promoters, like silanes, are being investigated. The aim of this paper was to study the adhesion and the anticorrosive behavior of a duplex system with a layer of glycidoxypropyltrimethoxysilane (γ-GPS) between the zinc and the coating. Polarization tests and corrosion potential measurements were done on the γ-GPS/galvanized steel to select the better anticorrosive pretreatment conditions for the application of an organic traditional paint. Dried and wet adhesion of the coating to the pretreated substrate was studied by the standard tape test. Salt spray test and electrochemical noise technique were employed to study the corrosion behavior of the duplex systems. Results showed that the films of γ-GPS formed on galvanized steel diminished the corrosion current of the metal, but they do not protect the substrate by a barrier effect. The incorporation of the pretreatment in the duplex system increased the adhesion of the paint, especially when the pretreated substrate was cured 1?h at 200?°C.     

Mechanical properties and adhesion of TiN monolayer and TiN/TiAlN nanolayer coatings

In this work, TiN monolayer and TiN/TiAlN nanolayer coatings were deposited on 100C6 (AISI 52100) steel substrate by Physical vapor deposited (PVD) magnetron sputtering system. The morphological characterization was evaluated using an atomic force microscopy. The mechanical properties were determined by nanoindentation test. The adhesion was investigated by both microindentation and scratch test. The results show that the TiN/TiAlN nanolayer coating have the more rough surface and the better mechanical properties and adhesion compared to TiN monolayer coating. The effect of microstructural and mechanical proprieties on the adhesion behavior was further discussed. It was found that the improvement in adhesion of nanolayer system is in part due to the increase in plastic deformation resistance and the enhancement of mechanical properties (hardness and elastic modulus) and to the structure with a small grain size and a high number of interfaces.     

Measurement of the practical adhesion of paint coatings to metallic sheets by the pull-off and three-point flexure tests

In this paper, we compare the practical adhesion measurements of alkyd, vinyl, epoxy, and polyurethane paints on cold-rolled steel using the pull-off and three-point flexure tests. It has been shown that (a) in the pull-off test, the ultimate load and ultimate strain values depend on the stud area. During trimming, cracks are created within the system which are responsible for a large decrease in the parameters measured. On the other hand, it is impossible to differentiate between the failure initiation and the failure propagation zones; (b) in the three-point flexure test, the area (W) subtended by the load/displacement curves corresponding to samples with and without stiffener does not depend on the bonded width or on the substrate compliance. After carrying out such a mechanical test, it is also possible to discriminate between failure initiation and failure propagation using appropriate tools for observation, such as scanning electron microscopy, and for analysis, such as electron microprobe analysis and Fourier transform infrared spectroscopy. W is shown to be representative of the failure initiation energy. To give a clear indication of the formation of the paint/substrate interphasial zone, we have studied the practical adhesion of different types of acrylic paint (thermoplastic acrylic binder filled with TiO₂, BaSO₄, or CaCO₃, with or without crosslinked polyurethane) applied onto aluminium substrates (treated in a sulphochromic acid bath). Five different types of failure initiation were observed, each type corresponding to quite different energies (W). Failure initiation takes place within the interphasial layer for thin coatings (thickness 70 μm). For thicker paint layers, cohesive failures were observed. A model showing the composition of the paint/metal interphase is proposed.     

A study of paint adhesion to polymeric substrates

In order to explore the fundamental mechanism of paint adhesion to polymer substrates the surface of polypropylene- ethylene propylene rubber (PP-EPR) blends was modified by flame or plasma treatments. The changes in surface composition and properties were investigated and discussed in light of the results of simple adhesion tests. The topography and surface properties of the PP-EPR samples were studied by employing various surface sensitive techniques. Additionally, the surface properties of the pre-treated PP-EPR were compared with the model polymers poly(methyl methacrylate) (PMMA) and polycarbonate (PC) displaying a poor and an excellent paint adhesion, respectively. Differential scanning calorimetry (DSC) measurements showed that the miscibility of the polymer substrate with paint components was an essential factor for the understanding of the adhesion mechanism. A general model of paint adhesion to polymer surfaces is proposed, where the degree of interdiffusion of the polymer chains of the substrate and paint in the interphase determines the adhesion strength.     

Interfacial adhesion measurement of a ceramic coating on metal substrate

The interfacial adhesion measurement of a ceramic coating on a metal substrate is studied by three-point bending (3PB) technique. In the measurement, interfacial cracks are induced during the 3PB test, and the interfacial energy release rate is calculated from the released energy per unit crack surface area during crack extension under the fixed displacement conditions. A finite element analysis (FEA) model encompassing the plastic behavior of the metal substrate is developed to simulate the 3PB test and extract the energy data. The inputs to the FEA model include the crack length, the maximum and critical loads corresponding to crack initiation, and the mechanical properties of the coating and substrate. A MoB/CoCr ceramic coating/stainless steel substrate system is investigated by the technique for demonstrating the utility of the technique.     

The role of ion-induced substrate damage in thin film adhesion strength

Variable-energy positrons are combined with Auger electron spectroscopy, scanning electron microscopy, and scratch test critical load measurements to study interfacial properties in thin film adhesion. This work complements an earlier investigation of the adhesion strength enhancement produced by ion bombardment of the substrate surface before deposition. In this study, we have investigated SiO₂ films deposited by radio-frequency (RF) sputtering onto stainless steel substrates. Extended ion bombardment etching leads to three related effects: the scratch test critical load is increased significantly, Auger electron spectroscopy shows a greater penetration of the film material into the substrate; and the interfacial positron annihilation signal is dominated by large, open-volume defects. These results are interpreted as confirmation that ion bombardment leads to the formation of microvoids in the interface layer and, consequently, to an increased adhesion strength by allowing mechanical interlocking between the coating and the substrate.     

拉开测试法评定机械镀锌层的结合强度

分别采用划格法和拉开法测量了机械镀锌层与A3钢片的结合强度。结果表明:划格法只能定性地对镀层结合性能进行评价,其结果不能准确反映镀层的结合强度;拉开法则能较准确地定量反映镀层的结合强度,且随着镀层厚度的增加,镀层结合强度呈下降趋势。     

On the role of sulfurization in adhesion of nitrile rubber to brass

The effects of conditions — in which nitrile rubber was vulcanized in contact with metallic substrates (e.g. brass or steel) — on the adhesion strength of rubber-substrate joints were investigated. The adhesion strength was estimated by measuring the peel resistance when the metallic foil was separated from the vulcanizate film. When the raw rubber was vulcanized, the plots of 'adhesion strength-versus-vulcanization parameters' (such as temperature and length of the process) show maxima, the pattern (character) of which depends on the substrate material. For joints with steel, the maximum in adhesion strength results from variations in the mechanical properties of the rubber which undergoes transition from the viscous flow to the highly elastic relaxation state in the course of vulcanization. The authors believe that the strength of adhesional bonding in rubber/brass systems depends on the mechanical properties of the sulfide film formed on the substrate in the course of vulcanization of the rubber. Experimental results which support the cohesive nature of the failure in the sulfide film in rubber/brass joints are presented in this paper.     

Polyethylene/polyurethane blends for improved paint adhesion

Polyolefins have low free surface energy that prevents good wettability of adhesives or paint emulsions to their surface. This work shows that adhesion of olefin block copolymers (OBC) to a polyurethane-based paint can be significantly improved by blending thermoplastic polyurethane (TPU) into OBC. Furthermore, blend morphologies near the paint/polymer interface, and surface compositions of injection molded plaques, were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) in order to explore the underlying mechanism of paint adhesion to TPU/OBC blends. It was found that for 35 wt% and 25 wt% TPU loading, the top paint layer is well-attached at the interface, whereas for 15 wt% loading, there was incomplete wetting of the paint, and a gap between the polymer substrate and paint was apparent. XPS and SEM gave consistent results demonstrating that outermost surface composition of TPU in these blends is slightly higher than in the bulk. It is speculated here that, during painting and the subsequent drying step, polyurethane chains from the paint diffuse into the blend substrate and entangle with TPU in the blend. The entanglement between paint and substrate generates a physical link that provides adhesion.     

The investigation of adhesion and fatigue properties of TiN/TaN multilayer coatings

TiN/TaN multilayer coatings exhibit excellent mechanical properties when compared to single layer nitride coatings. In this study, TiN/TaN multilayer coatings were deposited on Mo-alloy and W-alloy substrates by CFUBMS. The structural and mechanical properties of coatings were analysed using XRD, EDS, SEM and a micro-hardness tester, respectively. To determine the adhesion and fatigue behaviour of the coatings were performed a scratch test in two modes that a standard mode with progressive loading and sliding-fatigue multimode operation with unidirectional sliding, respectively. A microscope was used to characterize adhesion and fatigue failures. The structural, mechanical, adhesion and fatigue properties of TiN/TaN multilayer coatings significantly changed depending on the substrate.     

Influence of corona treatment on adhesion and mechanical properties in metal/polymer/metal systems

The effect of corona treatment (CT) on the adhesion at the metal–polymer interface was studied. Metal/polymer/metal laminates were manufactured by the laboratory roll‐bonding process with preliminary corona surface treatment of the polymer core: a polyethylene and polypropylene sheet as well as steel sheet. It was treated with corona discharge to increase its surface energy and the adhesion to metal, an austenitic steel. The adhesion, which was measured by T‐peel and shear tests, was increased by 43% of crack peel and 22% of mean peel resistance respectively, after 120 s CT. On the basis of scanning electron spectroscopy observations, improvements in the adhesive properties were attributed to the change in the interfacial morphology. In mechanical tests, yield and tensile strengths were strongly influenced by CT, indicating that these laminates were sensitive to interfacial phenomena. However, elongation at rupture of the composites was found to be unchanged. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

A new method to measure the adhesion capability of the metallic surface under shear loading using a modified Arcan test

The single lap shear test is considered by carmakers as a standard test to control the adhesion of a bonded assembly. In some special cases, when thin steel surfaces are bonded to a structural toughened epoxy-based adhesive, interfacial failure could occur using this mechanical test. Understanding the contribution of the steel surface on the failure mechanisms using the single lap shear test is complex: heterogeneous distribution of stresses, contributions of edge effects, plasticity of the sheet metal, and stiffness of the specimen. It is very difficult to determine failure criteria using the single lap shear test for the interfaces.

This work proposes a new method to measure the adhesion capability of the metallic surface under a well-controlled loading. The method is based on the modified Arcan test in shear loading which is adjusted to steel plates. Three different types of surfaces were characterised experimentally and numerically with different adhesion behaviours regarding their failure patterns. The new modified Arcan test is a suitable test to identify the properties of the interfaces in the bonded assemblies using strain and energy criteria.     

Measuring adhesion to poly(olefins): The role of adhesion promoter and substrate

The use of thermoplastic poly(olefins) in the automotive industry continues to proliferate due to their decreased cost and weight and increased recyclability in comparison to thermoplastics such as poly(carbonate) alloys or poly(urethanes). An attribute that continues to hamper the widespread introduction of thermoplasticpoly(olefins), in particular thermoplastic olefin (TPO, a blend of impact copolymer and elastomer), into additional automotive components, however, is its poor surface wettability and adhesion. Adhesion promoter formulation, both in terms of resin composition and solvent variation, has been known to influence the adhesive propensity of topcoats when analyzed by typical tests such as peel strength. It has long been disputed, however, that peel strength is not a true measure of paint adhesion since it artificially introduces a film between the paint and the adhesion promoter to enable one to perform the test. In contrast, this paper discusses the use of a newly developed in-situ adhesion test, described as compressive shear delamination (CSD), to quantify the adhesive/cohesive propensity of coatings to a variety of TPO substrates. The effect of solvent type and chlorinated poly(olefin) (CPO) adhesion promoting resin on the adhesion/cohesion of topcoats to TPO is described. Chlorinated poly(olefin) type, followed by solvent variation, was shown to have the most significant impact on the adhesion/cohesion of topcoats. This newly described CSD protocol for determining the weak link in painted plastic may have a significant impact on the choice of topcoat, adhesion promoting primer formulation, and substrate in particular automotive applications. Presented at the 78th Annual Meeting of the Federation of Societies for Coatings Technology, on October 16–20, 2000, in Chicago, IL. Dearborn, MI 48121 Santa Barbara, CA Evansville, IN     

Characterization of adhesion performance of topcoats and adhesion promoters on TPO substrates

Adhesion of organic coatings to thermoplastic olefin (TPO) substrates in automotive applications has been an issue for makers of automotive parts since TPO was first used in exterior applications, primarily fascia. A widely used technique for assuring paint adhesion to TPO is the use of adhesion promoter primers based on chlorimated polypropylenes (CPO). Much research has been focused on understanding the forces involved at the interfaces of substrate, adhesion promoter, and topcoats resulting in the adhesion or the loss of adhesion in various environmental conditions. This study correlates the adhesion performance of CPO and nonchlorinated adhesion promoters (NCPO) as measured by peel strength with properties observed through microscopy techniques. Adhesion performance of CPOs, NCPOs, and blends are quantified through the use of 90° and 180° peel strength studies. Surface characteristics of adhesion promoters applied over a TPO substrate and cured at various temperatures are examined through the use of atomic force microscopy (AFM).     

Quantitative measurement of adhesion between polypropylene blends and paints by tensile mechanical testing

A tensile mechanical test suiable to measure the adhesion between brittle coatings and ductile substrates was applied to measure the adhesion of painted layers on polypropylene blends. The test involves the tensile deformation of the painted assembly, resulting in the periodic cracking of the brittle coating on the ductile substrate. The interfacial shear strength was determined by measuring the strength of the coating, the thickness of the coating, and the average width of paint fragment after the crack density reaches saturation. Apparent interfacial shear strength was obtained for different paints on the same kind of blend, which gave consistent results over the experimental strain rate range from 10^?4 to 10^?3 sec^?1. Interfacial delamination was studied by optical microscopy (OM) and transmission electron microscopy (TEM). The delamination was observed to mainly occur near the adhesion promoter and substrate interface.     

A study of the effect of surface pre-treatment on the adhesion of coatings

This paper deals with the study of effects of mechanical surface preparation on the adhesion of coating with high content of zinc dust. Five kinds of mechanically blasted surfaces were studied. The following were used as abrasives: steel shot, steel grit, brown corundum oxide and zirblast. The last surface type was modified by MBX Blaster technology (mechanical bristle blasting). The surfaces topography was quantified by a roughness profilometer. The shape and size of the incurred inequalities on the modified surfaces were studied using 3D microscope images of the surface. The purity of the surfaces after pre-treatment was evaluated by impurity glued on the tape and measuring the reflection of light from the surface. Fractal analysis was used to evaluate the diversity of inequalities on the prepared surfaces. Cross-sections were also taken of the prepared surfaces. The prepared surfaces were coated with zinc-filled coating. The adhesion of the coating to the substrate was evaluated by a pull-off test after curing the coating (as sprayed), as well as after exposure to severe corrosive environments. The best adhesion of the coating was found for the coating applied to the substrate which had been pre-treated with brown corundum and steel grit.     

Nanosilicon dioxide/o-phenylenediamine hybrid composite as a modifier for steel paints

Different amounts of the hybrid composite nano SiO₂/o-phenylenediamine were added to a typical paint being used for protecting steel against corrosion to increase its protection efficiency. The nano features of the composite were confirmed by different electron microscopic investigations. It was found that the protection efficiency of the paint increased significantly as well as its adhesion to the steel surface increased. These conclusions had been inferred from both potentiodynamic polarization and electrochemical impedance spectroscopy techniques. To confirm the previous concept salt spray test and adhesion force measurements were carried out. The results were interpreted in terms of the filling properties of nano SiO₂ and adsorption/hardening power of o-phenylenediamine.     

Thermomechanical analysis and modeling of the extrusion coating process

During the extrusion coating process, a polymer film is extruded through a flat die, stretched in air, and then coated on a substrate (steel sheet in our case) in a laminator consisting of a chill roll and a flexible pressure roll. The nip, i.e. the area formed by the contact between the pressure and the chill rolls, constitutes the heart of the extrusion coating process. Indeed, in this region, some of the most critical properties, such as adhesion, barrier properties, optical properties, are achieved or lost. In this article, we first present an experimental investigation of the coating step, which enables to characterize the leading thermomechanical phenomena. It is shown that there is no polymer macroscopic flow in the nip, but a local flow within the asperities of the steel substrate surface. This microscopic flow, at the interface between the film and the substrate, is slowed by strong cooling conditions in the nip. Several models are then proposed, giving access to the temperature profile through polymer thickness and substrate, the pressure distribution in the nip as well as the behavior of the polymer melt in the nip at the interface with the substrate. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Interfacial adhesion and water resistance of stainless steel–polyolefin improved by functionalized silane

The adhesion strength and water resistance of stainless steel and adhesive resin composites determine the long‐term performance of wires and cables; however, adhesion at stainless steel interfaces is difficult. Herein, we prepared ethylene acrylic acid/linear low‐density polyethylene (EAA/LLDPE) blends with good mechanical and adhesive properties. Silane was anchored to the surface of stainless steel. The effects of silane functionalization on the adhesion surface were investigated by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The reaction mechanism between the stainless steel, silane, and EAA/LLDPE revealed adhesion was optimized when a 3:7 volume ratio of 3‐methacryloxypropyltrimethoxysilane (MEMO): 3‐aminopropyltrimethoxysilane (A‐1110) was used to modify the stainless steel substrate. SEM images of EAA/LLDPE film peel surfaces found the silane‐treated stainless steel substrates produced rough surfaces with a uniform void indicating the silane treatment enhanced the stainless steel and EAA/LLDPE film interaction. The stainless steel and EAA/LLDPE film adhesion and water resistance improved and the peel strength after water resistance testing at 68°C for 168 h increased from 3.18 N/cm to 9.37 N/cm compared to untreated stainless steel. Silane‐modified stainless steel and EAA/LLDPE blend film composite materials demonstrate potential for application in wires and cables used in environmental corrosion‐resistant applications. POLYM. ENG. SCI., 59:1866–1873, 2019. © 2019 Society of Plastics Engineers     

Adhesion and adhesion degradation of a pressure sensitive tape on carbon steel

Corrosion protection of carbon steels by organic coatings is dependent on a good adhesion between coating and substrate. In this work the blister test method was used to study the adhesion of a pressure sensitive tape applied on carbon steel. Deionized water was used to pressurize a blister formed by the tape covering a through-hole in the steel substrate. Values of adhesion strength as measured by the strain energy release rate were determined for two different blister pressurization rates or water injection rates. The adhesion strength was higher for the larger injection rate, which is expected for pressure sensitive tape. These values were probably overestimates of the true adhesion strength owing to plastic yielding of the membrane. Resistance to adhesion degradation near coating defects or macroscopic scribes was characterized using a height regulating scanning Kelvin probe on samples exposed to sodium chloride solution or a salt spray environment. Although the tape exhibited good barrier properties to water and ions, cathodic delamination was observed near the scribe after salt spray exposure. Wet/dry cycles were more aggressive than continuous salt spray exposure, since during continuous exposure corrosion products are washed away. It was observed that the oxide layer grows to a larger extent during wet/dry cycles; therefore, acceleration of the delamination process is probably associated with a “wedge effect” of the oxide on the interface.