Calorimetric Measurements of The Heat Generated by The Peel Adhesion Test

The peel test is a simple mechanical test commonly used to measure the adhesion of flexible films bonded to rigid substrates. When the film is deformed elastically during peeling, the peel force is a direct measure of the strength of the interface. However, when plastic deformation takes place, the work of detachment is much larger than the thermodynamic work of forming the fracture surfaces. Simultaneous mechanical and calorimetric measurements of the work of detachment and the heat generated during the peeling of polymeric films from metal substrates and metal films from polymeric substrates have been made. An energy balance for peeling has been proposed. Most of the work of peeling was consumed by plastic deformation. The peeled polymer dissipated approximately one half of the work of peeling as heat and most of the remainder was stored in the peeled material. The peeled metal dissipated most of the work of peeling as heat.     

Study of a 'T'-type peel test on a metal/polymer/metal sheet sandwich

This paper describes the specific 'T'-type peel mode in the case of a metal/polymer/metal sheet sandwich and gives experimental results on the influence of plastic deformation in the metallic substrates on the peel energy. We propose an experimental method of carefully determining the peel energy of a metal-polymer interface in a sandwich structure. Based on the mechanical properties of the stainless steel substrates and the maximum curvature of the metallic sheet measured experimentally during the peel test, several expressions for the clastoplastic deformation energy of the metal substrates are given. It is noteworthy that the curvature of the metal substrate layers depends not only on the mechanical properties of the material, but also on the work necessary to overcome the interfacial or cohesive forces. It is shown that even for thin metallic substrates (0.1 mm thick stainless steel), the work absorbed by the deformation represents roughly 50% of the total measured energy. During peeling the same specimen at different rates, the propagation peel force is higher or lower than the initiation force depending on the previous curvature of the metal sheets.     

Processing and characterization of multilayer films of poly(ethylene terephthalate) and surface-modified poly(tetrafluoroethylene)

Multilayer films were prepared from poly(tetrafluoroethylene) (PTFE) and poly(ethylene terephthalate) (PET) films together with using an adhesion promoting layer (tie-layer) consisting of ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer and low density polyethylene (LDPE) blend. Na/naphthalene treatment and subsequent acrylic acid grafting were applied on the surfaces of PTFE for chemical modification. FT-IR spectroscopy, XPS analysis and surface energy measurements were performed to characterize the modified PTFE films. The analyses showed defluorination and oxidation of PTFE surface, and supported the acrylic acid grafting. The surface energy of modified surfaces enhanced with respect to unmodified one, which promoted adhesion. The multilayers were subjected to T-peel tests to measure the adhesion strength between PET and modified PTFE. Peel strength between the films increased with increasing E-MA-GMA amount in the tie-layer. A proportional dependence of peel strength on Na/naphthalene treatment time was observed for multilayers containing acrylic acid grafted or ungrafted PTFE. From SEM analysis, it was observed that the texture of the PTFE surface after modifications became rougher when compared to untreated PTFE. The peeled surfaces were also analyzed by SEM. The micrographs evidence that the energy absorbing mechanism is the plastic deformation of the tie-layer, which is responsible for obtaining high peel strengths.     

Studies on the adhesion of polyimide coatings on copper foil

The peel strength and the color of the copper foil peeled at 90 degrees from five different polyimide films were studied. The interfacial surfaces of copper foil and polyimide were examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersion analysis by X-ray (EDAX). There is a correlation between peel strength, and the color of the interfacial side copper caused by oxygen diffusion. Study of the imidization process carried out in vacuum indicates that the geometric arrangements of the atoms of polyimide also play a very important role in peel strength.     

Adhesion and Crosslinking in Epoxy Resin/Steel Assemblies

A novel technique has been employed to investigate the development of interfacial bonding between steel and epoxy resins. Whereas such systems are usually rigid, precluding use of the very informative peel test, we have used spring steel as a flexible adherend and peeled this from the (relatively) rigid crosslinked polymers. Peel energy has been assessed for 180° and 90° tests, using a cylindrical former to limit irreversible deformation of the steel. Cure cycles for the resins DGEBA/DDA and DGEBA/DDS have been studied using DSC, and results exploited in such a way that peel tests could be effected on assemblies for which the total degree of polymer crosslinking was standardised, yet polymer/steel contact time during crosslinking was varied. The degree of potential reactivity of the polymers with respect to the steel was thus controlled. It was found, for both polymers, that measured adhesion energy was an approximately linear function of the fraction of crosslinking agent that reacted whilst epoxy/steel contact was maintained. Master curves for the two systems have been plotted, irrespective of cure conditions, the DGEBA/DDS system presenting better adhesion. Although no direct evidence of type and/or number of interfacial bonds is presently available, a simple argument suggests that chemical reactions occurring at ca. 1% of available surface sites may markedly improve adhesion.     

Ageing of corrosion resistant steel/rubber/composite hybrid structures

One of the major challenges when preparing reliable hybrid structures is the adhesion between different components. Besides enduring the specific stress state, hybrid structures should maintain the required properties in the service environment without degradation. In this study, the environmental resistance of stainless steel/rubber/GFRP (glass fibre reinforced plastic) hybrid structures were tested by exposure to hot, moist and hot/moist environments and after the ageing by peel testing. Two different stainless steel surface finishes and two different rubber grades were investigated. The results were compared with the properties of a mild steel/rubber/GFRP structure. Both mild steel/rubber and composite/rubber structures are used in industrial applications, such as in vibration damping devices and in automotive components.The peel tests showed that with right rubber compounds, stainless steel/rubber and GFRP/rubber interfaces can maintain their properties even in harsh hot/moist environments to such an extent that the interfacial strength of the joint is higher than the cohesive strength of the rubber. This enables the use of rubber's cohesive fracture properties instead of the substrate/rubber interfacial properties when estimating the strength of the steel/rubber/GFRP hybrid structure. In addition, based on the current study, time-consuming stainless steel pre-treatments are not needed but the stainless steel can be in the as-received stage. According to the chemical analysis even before and after the harsh hot/moist exposure used, none of the studied rubber grades had degraded. Thus, we conclude that it is possible to manufacture environmental resistant stainless steel/GFRP hybrid structures with the aid of EPDM rubbers.     

利用市售不锈钢箔制备氮化硼纳米线

Chemical vapor deposition growth of one-dimensional nanomaterials usually demands substrates that have been coated with a layer of catalyst film. In this study, a green process to synthesize boron nitfide （BN） nanowires directly on commercial stainless steel foils was proposed by heating boron and zinc oxide powders under a mixture gas flow of N2 arid 15% H2 at 1100℃, and a large quantities of pure h-BN nanowires have been produced directly on commercial stainless steel foil. The stainless steel foils not only acted as the substrate but also the catalyst for the nanowire growth. The synthesized BN nanowires were characterized by X-ray diffraction, scanning and transmission electron microscopes, X-ray energy dispersive spectrometer and photoluminescence spectroscopy, The nanowires also possess strong PL emission bands at 515, 535, and 728 nm.     

Adhesion of Polyethylene to Metals: The Role of Surface Topography

Previous work established the importance of the fibrous substrate topography in obtaining good adhesion of polyethylene to matt black oxide films formed on copper in alkaline solution. In this paper the effect of the very rough surface topography is shown to be general. Anodising treatments for copper and zinc and a high temperature oxidation for steel are described which give a very rough surface consisting (respectively) of fibrous, dendritic and blade-like growths. The peel strength of polyethylene to these substrates is high even under circumstances, for example when the polymer is stabilised with anti-oxidant, where adhesion to a chemically similar smooth surface is low. The high peel strength is associated with large amounts of energy being dissipated during peeling in plastic deformation of the polymer near the interface. It is suggested that this is caused by the development of high shear stress concentration at the fibre ends causing yielding in a large volume of polymer.     

304不锈钢箔的表面处理和粘接工艺研究

研究不同表面处理和胶粘剂实现5μm胶层对0.05 mm厚304不锈钢箔的粘接。试验表明:不锈钢表面粗糙度、偶联处理、胶粘剂和工艺对粘接效果有影响。最佳工艺:不锈钢箔先用丙酮清洗,于刻蚀剂中室温震荡5 min,水和乙醇清洗,再浸泡于浓度为0.5%KH-550乙醇水溶液30 s,乙醇清洗,晾干上胶,保温压粘,不锈钢箔剥离强度可达到9.4 N/cm,并耐丙酮等溶剂浸蚀。     

Study on brown oxidation process with imidazole group,mercapto group and heterocyclic compounds in printed circuit board industry

The adhesion strength of the interface between copper foil and resin is an important technological parameter for applications in microelectronics. In this study, a new brown oxidation solution of copper foil, including the recipe composition and reliability tests, was fully discussed. We provided an overview of brown oxidation process used in the semi-flexible printed circuit boards production industry by investigating the brown oxide film. The morphology of the copper oxide film was changed from lamellar structure to honeycomb structure with the increasing of oxidation time. The peel adhesion strength of the Cu/polyimide laminates was increased from about 2–16 N/cm by altering the immersion time and the concentration of inhibitors in brown oxidation solution. Scanning electron microscopy, peel tests and X-ray diffraction indicated that the higher adhesion strength was resulted from the rougher surface and the proper etching depth of copper foil, which was caused by chemical reactions on the interface surface of copper foil.     

Adhesion behavior of different annealed polyphenylquinoxaline foils treated using low pressure plasma

The aim of this study was to investigate the adhesion behavior of polyphenylquinoxaline (PPQ) foils. PPQ foils were initially produced and then annealed in vacuum furnace at different temperatures. The surface of PPQ was activated with GHz‐low pressure plasma (lp‐plasma) using oxidative (O₂) and noble (Ar, Ar/He) gases. An epoxy adhesive was used to glue the PPQ foil with a sheet of steel. The adhesions of foils were examined using 90°‐peel test. Observations from scanning electron microscopy (SEM) and atomic force microscopy (AFM) in addition to the gravimetry measurements were used to interpretate the effects of plasma treatment of adhesion of foils. The results showed that the peeling resistance values were significantly dependent on plasma treatment time and power as well as annealing conditions. In case of PPQ foils where the adhesion was significantly enhanced, it was observed that the fracture changed from adhesion mode at the interface between the adhesive layer and the PPQ foil to cohesive mode, which was seen either in the layer nearby the PPQ surfaces or in the foil itself. Furthermore, furrowed structures were observed at the fracture surface and they were oriented transversely to the peeling direction. SEM and AFM graphs showed that the surface roughness of PPQ foils increased significantly with increasing plasma treatment time and it was more pronounced when using oxidative than noble gas. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39949.     

The Effect of Bubbles at the Interface on the Adhesion of Polyethylene to Metals

By use of a blowing agent bubbles of a few hundred microns diameter were introduced at the interface of copper and steel substrates coated with low density polyethylene. The presence of the bubbles leads to an improvement in peel strength. An explanation is put forward in terms of a suggested stress perturbation produced by the bubbles which leaves the interface itself relatively lowly stressed and leads to the expenditure of work in plastic deformation of the polymer away from the interface. Support for the explanation was obtained by photoelastic study of a model system and by scanning electron microscopy of the peeled surfaces.     

An Elasto-Plastic Investigation of the Peel Test

This work outlines an elasto-plastic investigation of two common peel tests which use high and low yield strength aluminium adherends. An elastic, large-displacement, finite element program has been extended to include elasto-plastic material behaviour. This has been used to analyse both peel tests. The adhesive stresses near the crack tip have been shown to be finite while the corresponding strains remain singular. A failure criterion based on a maximum adhesive strain has been used to predict the relative strengths of the peel test. The amount of energy dissipated in the plastic deformation of the peeling adherends has been assessed by a series of tests and has been shown to be a considerable amount of the total energy supplied to the peeling system. Further, although the two aluminium alloys considered have grossly different yield strengths the energies dissipated in plastic deformation are similar. Material data for the finite element analysis and the plastic work calculations have been obtained from uniaxial tensile tests of both the adherends and the adhesive and actual peel strengths have been measured in a series of peel tests.     

The use of peel tests to examine the self adhesion of polyimide films

Peel tests were used to examine the adhesion between two layers of the polyimide pyromellitic dianhydride-oxydianiline (PMDA ODA). The main thrust of this work was to examine these tests with particular emphasis on yielding in bending of the peeled strips. Two peel geometries and a range of sample thicknesses were used to study interfaces whose strength could be varied over a wide range by changing the cure schedule. The peel strength varied with strip thickness and often reached a peak at an intermediate thickness. The results were shown to agree qualitatively with a combination of two theoretical models for the effects of yielding on peel tests. It was also found that a second problem of polyimide adhesion, the effect of solvent swelling, could significantly enhance the adhesion between polyimide layers.     

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     

An Elasto-Plastic Investigation of the Peel Test

This work outlines an elasto-plastic investigation of two common peel tests which use high and low yield strength aluminium adherends. An elastic, large-displacement, finite element program has been extended to include elasto-plastic material behaviour. This has been used to analyse both peel tests. The adhesive stresses near the crack tip have been shown to be finite while the corresponding strains remain singular. A failure criterion based on a maximum adhesive strain has been used to predict the relative strengths of the peel test. The amount of energy dissipated in the plastic deformation of the peeling adherends has been assessed by a series of tests and has been shown to be a considerable amount of the total energy supplied to the peeling system. Further, although the two aluminium alloys considered have grossly different yield strengths the energies dissipated in plastic deformation are similar. Material data for the finite element analysis and the plastic work calculations have been obtained from uniaxial tensile tests of both the adherends and the adhesive and actual peel strengths have been measured in a series of peel tests.     

Improving interfacial adhesion between thermoplastic polyurethane and copper foil using amino carboxylic acids

A chemical methodology to improve the adhesion between copper foil and a thermoplastic polyurethane (TPU) matrix is reported. The copper foil (0.127 mm thickness) was treated with aminocarboxylic acid‐based coupling agents such as 6‐aminohexanoic acid and 4‐aminobenzoic acid. 3‐Aminopropyl trimethoxysilane was also used as a conventional silane coupling agent for comparative studies. The interfacial adhesion between copper foil and laminated TPU was examined by means of peel adhesion test, scanning electron microscopy, and attenuated total reflection‐infrared spectroscopic methods. The treatment of copper foils with 6‐aminohexanoic acid resulted in improved adhesion, which was equal to that of the silane‐treated system. The mechanism of how the coupling agents strengthen the interfacial adhesion between TPU and copper foil is discussed. The solution concentrations of the coupling agents were optimized with respect to the peel adhesion of the interface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A peel adhesion study of electroless Cu layers on polymer substrates

The peel adhesion between two different electroless-plated Cu layers and polymer substrates was studied. Cu was electroless-plated onto polymer substrates using two different commercial solutions with different compositions. The adhesion strength between the electroless Cu layers and polymer substrates was measured with the 90° peel test. The adhesion was influenced by the coverage, grain size, and the thickness of the electroless Cu layer. Poor coverage of the electroless Cu layer increased the density of the pores at the interface between the Cu layer and the substrates, thereby degrading the adhesion strength because of a decrease in the contact area. In addition, the electroless Cu layers with larger nodules and larger grains were softer and had higher peel adhesion since the soft and ductile Cu layer promoted a greater amount of plastic deformation during the peel test. This led to enhanced peel adhesion. Finally, as the thickness of the electroless Cu layer increased, the peel adhesion decreased. The thicker Cu layers are not easily bent. Poor bending of the Cu layer induced less plastic deformation, causing a decrease in the peel adhesion. In conclusion, soft and thin electroless Cu layers with greater coverage are preferred in order to obtain good adhesion.     

Mechanical effects in peel adhesion test

—Mechanical effects in the peel strength of a thin film have been studied both experimentally and theoretically. It has been found that the adhesion strength measured by the peel test is a practical adhesion (an engineering strength per unit width) and does not represent the true interface adhesion strength. The measured value may represent a multiplication of the true interface adhesion and other work expended in the plastic deformation of the thin film. The contribution of the latter to the peel strength is found to be, sometimes, of the order of 100 times higher than the former. It is found that the major controlling factors in the peel strength are the thickness, Young's modulus, the yield strength, the strain hardening coefficient of the film, and the compliance of the substrate as well as the interface adhesion strength. Even though the true interface adhesion strength is the same, a higher peel strength is obtained if the film is thinner or more ductile under the test conditions reported in this paper. The same effect can be obtained if the substrate is thinner in the case where the substrate is a soft elastic material, or if the substrate is thicker in the case where the substrate is a rigid material.     

Surface Energy and Adhesion Studies on Acrylic Pressure Sensitive Adhesives

The surface energy and adhesion dynamics of pressure sensitive adhesives-like networks (PSA-LNs) as mimics for PSAs were studied using JKR-based contact mechanics and peel tests. Acrylic acid (AA) was co-polymerized with 2-ethyl hexyl acrylate (2-EHA) and 1,6-hexane diol diacrylate (HDDA) to create PSA-LNs. The measured surface energy (27 to 31 mJ/m²) was sensible as surmised from their structure. Acrylic acid content increases the surface energy, threshold adhesion energy and adhesion hysteresis of PSA-LNs. Measurements of adhesion dynamics showed a dependence of adhesion energy to the 0.6-0.8 power of crack speed, depending upon the model chosen for analysis of the data. When compared with actual pressure-sensitive adhesive tape peel tests, the adhesion dynamics data predicted the peel strength. This study shows a direct relationship between threshold adhesion energy, crack propagation mechanics and peel strength measurements.