Adhesion Of Elastomers Research Articles

Application of the time-temperature superposition principle to the mechanical characterization of elastomeric adhesives for crash simulation purposes

In the automotive industry, finite element simulation is widely used to ensure crashworthiness. Mechanical material data over wide strain rate and temperature ranges are required as a basis. This work proposes a method reducing the cost of mechanical material characterization by using the time-temperature superposition principle on elastomeric adhesives. The method is based on the time and temperature interdependence which is characteristic for mechanical properties of polymers. Based on the assumption that polymers behave similarly at high strain rates and at low temperatures, a temperature-dominated test program is suggested, which can be used to deduce strain rate dependent material behavior at different reference temperatures. The temperature shift factor is found by means of dynamic mechanical analysis according to the WLF-equation, named after Williams, Landel and Ferry. The principle is applied to the viscoelastic properties as well as to the failure properties of the polymer. The applicability is validated with high strain rate tests.

The Mechanism of Adhesion Improvement of Elastomeric Silicone Sealants to Difficult-to-Bond Polymeric Substrates through Reactive or Interpenetrating Molecular Brushes

Abstract High-quality and durable adhesion of elastomeric adhesives to metallic, ceramic, and organic substrates is essential to a broad range of industries, e.g., building and construction, automotive, electronic, aerospace, biomedical, and others. The principles of engineering substrate surfaces through grafted connector molecules are discussed in this paper. In particular, two important modes of interaction for surface-grafted “molecular brushes” are investigated and experimentally verified. It is demonstrated that the inclusion of silicone- and/or amine-terminated graft molecules, such as silanes or polyethyleneimines, at polymer interfaces, results in the formation of strong molecular bridges between a range of organic substrates and elastomeric sealants leading to significantly improved bonding. The technology has been successfully adopted by global automotive industry for improving adhesion of a variety of adhesives and coatings to polyolefinic substrates.

Effect of Surface Roughness on the Adhesion of Elastomers to Hard Surfaces

The work presented started with the aim of trying to explain why clean smooth surfaces of materials such as metals brought gently into contact show no adhesion. The observation by Johnson Kendall & Roberts of adhesion between smooth surfaces of an elastomeric hemisphere and a rigid substrate suggested a model contact system with which the effect of surface roughness could be investigated experimentally. Moreover the Johnson-Kendal-Roberts (JKR) contact theory could be used to predict the effect of roughness on adhesion. The observations and predictions obtained are compared, and the implications for the contact of two rigid materials outlined. The limitations of the validity of the predictions are mentioned. Further studies of the adhesion to rough surfaces, in particular the phenomenon of enhanced adhesion at low roughness, will be discussed. Finally, more recent theoretical work is briefly referred to.

Comparison of the Mechanical Behaviour Between Stiff and Flexible Adhesive Joints for the Automotive Industry

Adhesive bonding is increasingly being used in structural applications such as in automotive joints. The theoretical analyses and experimental data are generally for rigid and strong epoxy adhesives. Elastomeric adhesives such as polyurethanes are used in structural applications such as windshield bonding because they present important advantages in terms of damping, impact, fatigue, and safety which are critical factors in the automotive industry. However, there are other structural applications in the main body where polyurethanes may also be used. The main objective of the present project is to compare the behaviour of structural joints used in the automotive industry, such as single lap joints and T-joints made of rigid adhesives, and those made of elastic adhesives in terms of stiffness, strength, impact, damping, and fatigue. The elastomeric adhesive selected was a polyurethane from Sika (Sikaflex® 256) and the structural adhesive selected was an epoxy from Huntsman (Araldite® AV138/HV998). The shear strength of the polyurethane is approximately four times lower than that of the epoxy. However, the polyurethane shear failure strain is 330%, whereas that of the epoxy is only 6%. The benefits of using elastomeric adhesives in structural adhesive joints used in the automotive industry are described, especially in terms of ductility, impact, and fatigue.

Flat Dry Elastomer Adhesives as Attachment Materials for Climbing Robots

In this paper, flat elastomers are proposed as an attachment material for climbing robots on less than a few micrometer-scale rough surfaces due to their energy-efficient, quiet, and residue-free characteristics. The proper elastomer is chosen by the use of the current adhesion, friction, and peeling elastomer-contact-mechanics models. Then, adhesion and friction properties of the chosen dry flat-elastomer thick films (Vytaflex-10) are characterized on acrylic and smooth and rough glass surfaces for variations in preloads, speeds, contact times, and elastomer thicknesses. A climbing robot with four-bar-based legged-body kinematics is designed and fabricated as simple and lightweight as possible to demonstrate the feasibility of the elastomers as attachment materials on relatively smooth surfaces. The robot utilizes a passive alignment system to make the footpads parallel to the surface on light contact, a peeling mechanism to minimize the detachment vibration, and a passive tail to minimize the pitch-back moment. Experimental results showed that the robot can climb stably on vertical, smooth surfaces in any direction and can walk inverted for a limited amount of time.

Influence of nm-Thick Atmospheric Plasma Deposited Coatings on the Adhesion of Silicone Elastomer to Stainless Steel

In this study the use of a nm thick plasma polymerised primer layer as a means of enhancing the adhesion of silicone elastomer to stainless steel was investigated. This primer layer was formed from tetraethoxysilane (TEOS) and polyhydrogenmethyl siloxane (PHMS). This primer mixture was nebulized into helium atmospheric pressure plasma formed using the PlasmaStream™ system. The resulting primer coatings were characterised using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, optical profilometry, scanning electron microscopy, spectroscopic ellipsometry and water contact angle measurements. The adhesion of the silicone elastomer was accessed using 45° peel strength measurements. This study investigated the effect of plasma jet to substrate distance on primer performance. Increased coating oxidation is observed as this gap between the jet orifice and substrate increases. The plasma power, measured using current and voltage probes was observed to increase with gap height. The corresponding coating thickness decreased from 450 to 100 nm as the gap height increased from 2 to 12 mm. Associated with this change there was a 38% reduction in silicone elastomer adhesion to the stainless steel surface, demonstrating that silicone elastomer bonded to the thinner and less oxidised primer layer exhibited superior adhesion.

Experimental Parameters Controlling Adhesion of Biomimetic Fibrillar Surfaces

The recently emerging interest in fibrillar biological attachment systems, as those found in the gecko, has led to the fabrication of micropatterned elastomer adhesion surfaces. Reported studies have demonstrated that measurements on micropatterned surfaces are affected by experimental parameters not relevant for flat samples. The present paper investigates the influence on adhesion values of the sample stiffness, the backing layer thickness, the ambient humidity, and of repetitive measurements at the same location. Measurements were performed on PDMS (Sylgard® 184) micropatterned surfaces possessing flat-ended pillars with 10 µm diameter and 10 µm height. We find that adhesion increased with decreasing sample stiffness and decreasing backing layer thickness, whereas it dropped when several tests were carried out at exactly the same location. For ambient humidities between 2 and 90%, no influence on adhesion performance was found.

Humidity influence on the adhesion of biomimetic fibrillar surfaces

Abstract The recent interest in fibrillar biological attachment systems, as found in the gecko, has led to the development of micropatterned elastomer adhesion surfaces. All reported studies have been performed at ambient humidity neglecting its possible influence on adhesion. The present paper investigates, for the first time, the effect of systematic changes in ambient humidity from 2 to 90 %. Adhesion measurements were performed on PDMS (Sylgard 184) surfaces possessing micropillars with flat-ended and hemispherical contact shape. The pillar radius was varied between 2.5 and 25 μm; the pillar aspect ratio was kept at 1. While the adhesion of a flat sample was not affected by humidity, we found that pillar size and shape influenced the sensitivity to humidity changes: Thinner pillars, with higher pull-off forces in the dry state, exhibited decreasing adhesion values, by up to 35 %, with increasing humidity. The effect was stronger for the hemispherical tip shape, where the positive effect of finer pillars was even reversed. Possible explanations for these effects, which may lower the reliability of biomimetic adhesion devices in the presence of humidity, are given.

The effect of plasma‐polymerised silicon hydride‐rich polyhydrogenmethylsiloxane on the adhesion of silicone elastomers

AbstractBACKGROUND: Silicone elastomers have outstanding material properties including good thermal stability, low electrical conductivity, biocompatibility and resilient physical and chemical properties. These elastomers, however, exhibit relatively poor adhesion to stainless steel, and the use of a nanometre thick plasma‐polymerised primer layer as a means of enhancing this adhesion was investigated in this study. The primer coatings studied consisted of polyhydrogenmethylsiloxane (PHMS), tetraethyl orthosilicate (TEOS) and mixtures of these two liquid precursors.RESULTS: The plasma‐polymerised primer coatings were deposited onto stainless steel substrates using a PlasmaStream™ atmospheric pressure plasma jet system. Deposited coatings were examined using ellipsometry, contact angle measurements, optical profilometry, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy. The adhesion of silicone elastomers bonded to the primed and bare stainless steel surfaces was assessed using 45° adhesion strength measurements. Elastomer adhesion was correlated with surface energy, thickness and roughness.CONCLUSION: An up to 15‐fold increase in adhesive fracture energy was observed for silicone elastomers bonded to the primed versus untreated stainless steel. The highest adhesion was observed for a coating deposited from a PHMS‐to‐TEOS precursor molar ratio of 3 to 1. Copyright © 2009 Society of Chemical Industry

Determination of the mixed‐mode fracture energy of elastomeric structural adhesives: evaluation of debonding buckling in fibre–metal hybrid laminates

ABSTRACTFibre–metal hybrid laminates combine layers of metal with laminates made of composites – polymeric matrix reinforced with glass‐fibre woven fabric. Interface behaviour plays a fundamental role in the overall properties of the hybrid material, especially in the failure mode by debonding buckling of the outermost metal layer. A proper measurement of adhesive fracture energy is required so as to avoid this early failure mechanism during bending. Tapered double cantilever beam test and dissimilar mixed‐mode bending test have been used in obtaining mode I and II contributions to the adhesive fracture energy. Data reduction for elastomeric adhesives has been modified in order to account for the variation in compliance during the test due to nonlinear behaviour of the material.

Qualitative and quantitative identification of copper oxides

AbstractThe quality, thickness, and chemistry of oxides on metal surfaces play a vital role in a variety of applications. Some of these include adhesion of elastomers to metal surfaces, solar cell efficiency, sealing of electronic packaging, reduction of friction during wet drawing, and degree of biocompatibility of biomaterials. However, contradictory results and misidentification of oxide layers on metallic surfaces have caused ambiguity in interpretation of results leading to incorrect use in industrial application. This study will focus on the effect of experimental parameters such as electrolyte composition and concentration, current density, coating, time constant, surface roughness, and concentration of depolarizer on cathodic reduction of oxides on metallic wires to yield precise measurement and correct identification of oxide layers. Copyright © 2008 John Wiley & Sons, Ltd.

Adhesion of thermoplastic elastomer on surface treated aluminum by injection molding

AbstractHybrid composites were prepared using insert injection molding without preheating. Thermoplastic elastomer (TPE) was overmolded on etched aluminum sheets having porous surface to provide large contact area between insert and TPE. The resulting bond strength was studied using a 180° peel test. The effect of aluminum microstructure and various processing steps of the surface treatment procedures on adhesion were studied. Maximum peel strength obtained was 9.33 N/cm using P2 treatment with alkaline‐acid pretreatment. Lowest peel strength of 1.68 N/cm was achieved by alkaline–acid treatment. Increasing insert thickness lowers the peel strength since large heat capacity of thicker insert cools the melt and limits penetration of the melt to insert microcavities. At certain insert thickness microcavities are impregnated by the melt and no additional effect can be obtained by decreasing the insert thickness. POLYM. ENG. SCI., 47:1187–1191, 2007. © 2007 Society of Plastics Engineers

Thermal Gradient Enabled XPS Analysis of PDMS Elastomer Adhesion to Polycarbonate

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTThermal Gradient Enabled XPS Analysis of PDMS Elastomer Adhesion to PolycarbonateDongchan Ahn, Nick E. Shephard, Patricia A. Olney, and Christopher S. McMillanView Author Information Dow Corning Corporation, 2200 W. Salzburg Road, Midland, Michigan 48686-0994 Cite this: Macromolecules 2007, 40, 11, 3904–3906Publication Date (Web):May 2, 2007Publication History Received13 March 2007Revised18 April 2007Published online2 May 2007Published inissue 1 May 2007https://doi.org/10.1021/ma070615hCopyright © 2007 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views872Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (39 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Elastomers,Interfaces,Silicones,Surface interactions,X-ray photoelectron spectroscopy Get e-Alerts

Analysis of the Effects of Interference and Sealant on Riveted Lap Joints

Much of the fatigue damage in aircraft structures can be linked to the stress concentration arising at the rivet/skin interface in fuselage lap joints. Fatigue damage can degrade the strength of the structure and reduce structural integrity. Elastomeric adhesives and sealants are applied to the lap joints before riveting to prevent entry of moisture, thus, preventing corrosion. The effect of the sealant on the residual stress state resulting from the rivet interference and subsequent load transfer has not been investigated. A three-dimensional finite element model of the riveting process is simulated to determine the effects of interference and sealant on the induced stresses. Both implicit and explicit finite element techniques are utilized to model the process. The finite element simulation is validated initially for both techniques with experiment. The analysis with sealant shows an increase in the residual hoop stress for the majority of the cases in comparison to the results without sealant.

Single-step replicable microfluidic check valve for rectifying and sensing low Reynolds number flow

This paper presents a new microfluidic check valve well suited for low Reynolds number flow rate sensing, micropump flow rectification, and flow control in lab-on-a-chip devices. The valve uses coupling between fluid movement in a channel and an elastomeric column (flap) suspended in the fluid path to generate a strong anisotropic flow resistance. Soft lithography-based molding techniques were used to fabricate the valve, allowing for a low-cost, single-step fabrication process. Three valves—having heights of 25, 50, and 75 μm, respectively—were fabricated and experimentally evaluated; the best of them demonstrated a maximum fluidic diodicity of 4.6 at a Reynolds number of 12.6 and a significant diodicity of 1.6 at the low Reynolds number of 0.7. The valve’s notable low Reynolds number response was realized by adopting a design methodology that balances the stiffness of the elastomer flap and adhesion forces between the flap and its seat. A pair of elastomer check valves integrated with a miniature membrane actuator demonstrated a flow rectification efficiency of 29.8%. The valve’s other notable features include a wide bandwidth response, the ability to admit particles without becoming jammed, and flow rate sensing capability based on optical flap displacement measurements.

Fracture and adhesion of elastomers and gels: Large strains at small length scales

Fracture and adhesion of elastomers and gels: Large strains at small length scales

弾性接着剤を利用した外装タイル張り工法の開発と普及

弾性接着剤を利用した外装タイル張り工法の開発と普及

Adhesion between Chemically Heterogeneous Switchable Polymeric Brushes and an Elastomeric Adhesive

We investigated the adhesive properties of binary heterogeneous polymer brushes made from end-functionalized polystyrene (PS) and poly(2-vinylpyridine) (P2VP) chains. The molecular organization of the mixed brush could be varied reversibly by exposure to selective solvents for PS (toluene) and for P2VP (acidic water). This exposure results in reversible switching of adhesive and wetting properties. The manner in which the adhesion switching occurs can be tuned by the composition of mixed brushes. However, the outer surface composition could be enriched more effectively in PS after the toluene treatment than in P2VP after the acidic water treatment. As a result, the mixed brush compositions that showed the largest difference in properties between an exposure to toluene and an exposure to water were the P2VP-rich compositions. Adhesive properties, tested against a soft hydrophobic pressure-sensitive adhesive (PSA) using a probe test, always showed smaller differences between solvent treatments than wetting properties with water, suggesting a much higher sensitivity of the hydrophobic/hydrophilic brushes to polar molecules than to nonpolar molecules.

Adhesion of elastomer layers to an interposed layer of filler particles

Adhesion of elastomers to filler particles was studied by interposing a single layer of particles between two layers of a crosslinked elastomer and peeling the sandwich apart. Carbon black particles increased the peel strength by up to 100% compared with autohesion of the elastomer layers. Silica particles also increased the adhesion, but by a smaller factor, and there were significant differences using different elastomers. Also, the strength of adhesion depended on the degree of crosslinking of the elastomer layers: at higher levels of crosslinking, both self-adhesion and adhesion to particles were reduced. Nevertheless, this simple experiment gives an indication of the relative strength of adhesion for different combinations of elastomer and reinforcing filler.

Crack blunting and the strength of soft elastic solids

When a material is so soft that the cohesive strength (or adhesive strength, in the case of interfacial fracture) exceeds the elastic modulus of the material, we show that a crack will blunt instead of propagating. Large–deformation finite–element model (FEM) simulations of crack initiation, in which the debonding processes are quantified using a cohesive zone model, are used to support this hypothesis. An approximate analytic solution, which agrees well with the FEM simulation, gives additional insight into the blunting process. The consequence of this result on the strength of soft, rubbery materials is the main topic of this paper. We propose two mechanisms by which crack growth can occur in such blunted regions. We have also performed experiments on two different elastomers to demonstrate elastic blunting. In one system, we present some details on a void growth mechanism for ultimate failure, post–blunting. Finally, we demonstrate how crack blunting can shed light on some long–standing problems in the area of adhesion and fracture of elastomers.