Modern State of Models for Fundamental Adhesion - A Review Extended Abstract

Possart, Wulff The Society of Adhesion and Interface 2002 접착 및 계면 Vol.3 No.1

Advanced adhesive technologies and demanding applications of adhesive joints can no longer be developed successfully by the traditional "trial and error" approach. Appropriate technical solutions require reference to a reliable basis of well-established scientific knowledge about the elementary mechanisms of adhesion (i.e. the 'fundamental adhesion') as they are responsible for the capability of the compound w transmit mechanical force between the adhesive and the substrate surface (i.e. the 'practical adhesion'). Adhesion mechanisms also influence the formation of polymer structure in the adhesive and the resulting macromolecular dynamics in the interphase that is formed in the adhesive near to the substrate. These manifold molecular factors rule the macroscopic behaviour of an adhesive bond line in terms of mechanical and other physical properties as well as in terms of durability. This paper reviews the level of refinement that understanding of fundamental adhesion has achieved up to now.

Wet adhesion and rubber friction in adhesive pads of insects

Federle, Walter The Society of Adhesion and Interface 2004 접착 및 계면 Vol.5 No.2

Many animals possess on their legs adhesive pads, which have undergone evolutionary optimization to be able to attach to variable substrates and to control adhesive forces during locomotion. Insect adhesive pads are either relatively smooth or densely covered with specialized adhesive hairs. Theoretical models predict that adhesion can be increased by splitting the contact zone into many microscopic, elastic subunits, which provides a functional explanation for the widespread 'hairy' design. In many hairy and all smooth attachment systems, the adhesive contact is mediated by a thin film of liquid secretion between the cuticle and the substrate. By using interference reflection microscopy (IRM), the thickness and viscosity of the secretion film was estimated in Weaver ants (Oecophylla smaragdina). 'Footprint' droplets deposited on glass are hydrophobic and form low contact angles. IRM of insect pads in contact showed that the adhesive liquid is an emulsion consisting of hydrophilic, volatile droplets dispersed in a persistent, hydrophobic phase. I tested predictions derived from film thickness and viscosity by measuring friction forces of Weaver ants on a smooth substrate. The measured friction forces were much greater than expected assuming a homogenous film between the pad and the surface. The findings indicate that the rubbery pad cuticle directly interacts with the substrate. To achieve intimate contact between the cuticle and the surface, secretion must drain away, which may be facilitated by microfolds on the surface of smooth insect pads. I propose a combined wet adhesion/rubber friction model of insect surface attachment that explains both the presence of a significant static friction component and the velocity-dependence of sliding friction.

Hot AC Anodising as a Cr(VI)-free Pre-treatment for Structural Bonding of Aluminium

Lapique, Fabrice,Bjorgum, Astrid,Johnsen, Bernt,Walmsley, John The Society of Adhesion and Interface 2003 접착 및 계면 Vol.4 No.2

Hot AC anodising has been evaluated us pre-treatment for aluminium prior to structural adhesive bonding. Phosphoric and sulphuric acid hot AC anodising showed very promising adhesion promoter capabilities with durability comparable with the best standard DC anodising procedures. AC anodising does not required etching prior to anodising and offers u pre-treatment time down to 20 seconds. The interface/interphase between the aluminium substrate and the adhesive was investigated in order to get a better understanding of the involved adhesion mechanisms and to explain the long-tenn properties. The alkaline medium formed at the oxide layer/adhesive interface has been shown to induce a partial dissolution of the oxide layer leading to the formation of metallic ions which diffuse in the adhesive (EPMA measurements). The effect of diffusion of the Al ions on adhesion and joint durability is still uncertain but studies showed that pre-bond moisture affected the joints durability and to some extent the diffusion length. specially for DC anodised samples. So far no direct correlation could be established between the diffusion length d and the joints durability but new trials with better control over the elapsed time between bonding and adhesive curing are expected to help getting a better understanding of the involved mechanisms.

Creep behaviour of flexible adhesives

van Straalen, Ijsbrand J.,Botter, Erik,van den Berg, Arnold,van Beers, Peter The Society of Adhesion and Interface 2004 접착 및 계면 Vol.5 No.2

Since flexible adhesives are used more and more in structural applications, designers should have a better understanding of its behaviour under various conditions as ultimate load, fatigue load, long-term load and environmental conditions. This paper focuses on long-term load conditions and its effect on flexible adhesives. The creep properties of both PU (PolyUrethane) and SMP (Silyl Modified Polymers) adhesives used for identical applications are considered. To investigate the creep behaviour tests under various conditions were done. The results of those tests are presented and compared. To evaluate these results an empirical method is proposed and discussed. An example illustrates the potential of this method. It is also shown that with use of a probabilistic calibration technique this method results into a simple rule, which can be used to calculate the creep for practical applications. For the studied adhesives, the creep performance of the SMP adhesive is shown to be of the same level or slightly better than of the two PU adhesives. In addition to this empirical method, the principles of a more complex theoretical based method are introduced. The potential of this method is illustrated and future research activities are drawn.

Wetting of Galvanised Steel by An Epoxy Adhesive: Effects of Surface Oil

Shanahan, M.E.R.,Greiveldinger, M. The Society of Adhesion and Interface 2002 접착 및 계면 Vol.3 No.1

The wetting properties of an uncured epoxy resin on both clean and oiled, galvanised steel have been studied. Since the polymer is very viscous at ambient temperature, and also with an aim to simulate industrial conditions, the spreading of drops of resin during a heating cycle (temperature increase at $10^{\circ}C/min$) was recorded and analysed. On clean steel, a contact angle, ${\theta}$, vs time, t, plot shows sigmoidal behaviour, whereas on the oiled substrate, spreading almost ceases in an intermediate stage. This strange behaviour is attributed to significant oil absorption by the polymer.

Highly Sensitive and Selective Fluorescent Chemosensors Specific for Pd²⁺ Detection

왕정,하창식,Wang, Jing,Ha, Chang-Sik The Society of Adhesion and Interface 2013 접착 및 계면 Vol.14 No.1

팔라듐은 치과 및 의료용 기구, 의료용 재료, 보석 및 자동차, 고기능성 점 접착제 등을 생산하는데 중요한 역할을 한다. 팔라듐을 이용하는 반응에서의 중요성에도 불구하고 팔라듐은 최종생성물에 잔존할 경우 인체에 해로운 독성을 가지고 있다. 그 중에서도 특히 $PdCl_2$는 독성이 가장 크다. 따라서 $Pd^{2+}$ 이온 검출은 매우 중요한 연구과제인데 그 중에서도 특히 형광분석법은 가장 손쉽고 경제적이면서 감도가 높고 선택성이 높은 방법으로 알려져 있다. 본 연구에서는 알파-카보닐로 치환된 파이렌 유도체인 감마-옥소-1-파이렌부틸산(OPBA)이 수용액에 금속이온으로 감도가 크고 선택성이 우수한 것으로 밝혀졌다. Palladium plays a pivotal role in the production of dental and medicinal devices, medicinal substances, jewellery, automobile and high-performance adhesives. Despite the frequent and fruitful use of such reactions, one major setback is the high level of palladium in the resultant compounds which can harm the human body. Among the palladium species, $PdCl_2$ is the most toxic. As a consequence it is desirable to detect the $Pd^{2+}$ cations by fluorescence spectra because it can provide an operationally simple and cost-effective detection method together with high sensitivity and selectivity. Herein, an ${\alpha}$-carbonyl substituted pyrene derivative, ${\gamma}$-oxo-1-pyrenebutyric acid (OPBA), was demonstrated to be a highly sensitive and selective fluorescent probe for $Pd^{2+}$ among the metal cations examined in aqueous solutions.

High-Performing Adhesive Bonding Fastening Technique For Automotive Body Structures

Symietz, Detlef,Lutz, Andreas The Society of Adhesion and Interface 2006 접착 및 계면 Vol.7 No.4

In modern vehicle construction the search for means of weight reduction, improving durability, increasing comfort and raising body stiffness are issues of priority to the design engineer. The intelligent usage of many materials such as high strength steel, light-alloys and plastics enables a significant vehicle weight reduction to be achieved. The classical joining techniques used in the automobile industry need to be newly-evaluated since they often do not present workable solutions for such mixed-material connections, for example aluminium/steel. Calculation/simulation methods have made progress as a key factor for broader and more cost-effective implementation of structural bonding. This will lead to reduction of spotwelds and accelerate the car development. A special focus of the paper is the use of high strength steel grades. It will be shown that adhesive bonding is a key tool for yielding the potential of advanced high strength steel for low gauging without compromising the stiffness. The latest status of adhesive development has been described. Improvements with physical strength and glass temperature as well as of process relevant properties are shown. Also the situation regarding occupational hygiene is treated, showing that by further spotweld point reduction the emission around the working area can be even lowered against the current praxis. High performing lightweight design cannot longer do without high performing crash durable adhesives.

A Strategy for the Simulation of Adhesive Layers

Ochsner, A.,Mishuris, G.,Gracio, J. The Society of Adhesion and Interface 2005 접착 및 계면 Vol.6 No.1

The high accurate simulation of very thin glue layers based on the finite element method is still connected to many problems which result from the necessity to construct a complicated mesh of essentially different sizes of elements. This can lead to a loss of accuracy, unstable calculations and even loss of convergence. However, the implementation of special transmission elements along the glue ling and special edge-elements in the near-edge region would lead to a dramatic decrease of number of finite elements in the mesh and thus, prevent unsatisfactory phenomena in numerical analysis and extensive computation time. The theoretical basis for such special elements is the knowledge about appropriate transmission conditions and the edge effects near the free boundary of the adhesive layer. Therefore, recently proposed so-called non-classical transmission conditions and the behavior near the free edge are investigated in the context of the single-lap tensile-shear test of adhesive technology.

Influence of the Adhesive, the Adherend and the Overlap on the Single Lap Shear Strength

da Silva, Lucas F.M.,Ramos, J.E.,Figueiredo, M.V.,Strohaecker, T.R. The Society of Adhesion and Interface 2006 접착 및 계면 Vol.7 No.4

The single lap joint is the most studied joint in the literature in terms of both theory and practice. It is easy to manufacture and the lap shear strength is a useful value for strength assessment and quality control. Simple design rules exist such as the one present in standard ASTM 1002 or in a recent paper by Adams and Davies. The main factors that have an influence on the lap shear strength are the type of adhesive, i.e. ductile or brittle, the adherend yield strength and the overlap length. The overlap increases the shear strength almost linearly if the adhesive is sufficiently ductile and the adherend does not yield. For substrates that yield, a plateau is reached for a certain value of overlap corresponding to the yielding of the adherend. For intermediate or brittle adhesives, the analysis is more complex and needs further investigation. In order to quantify the influence of the adhesive, the adherend and the overlap on the lap shear strength, the experimental design technique of Taguchi was used. An experimental matrix of 27 tests was designed and each test was repeated three times. The influence of each variable could be assessed as well as the interactions between them using the statistical software Statview. The results show that the most important variable on the lap shear strength is the overlap length followed by the type of adherend.

Micro Bonding Using Hot Melt Adhesives

Bohm, Stefan,Hemken, Gregor,Stammen, Elisabeth,Dilger, Klaus The Society of Adhesion and Interface 2006 접착 및 계면 Vol.7 No.4

Due to the miniaturization of MEMS and microelectronics the joining techniques also have to be adjusted. The dosing technology with viscous adhesives does not permit reproducible adhesive volumes, which are clearly under a nano-liter. A nano-liter means however a diameter of bonding area within the range of several 100 micrometers. Additional, viscous adhesives need a certain time, until they are cross linked or cured. The problem especially in the MEMS is the initial strength, since it gives the time, which is needed for joining an individual adhesive joint. The time up to the initial strength is with viscous, also with fast curing systems, within the range of seconds until minutes. Until the reach of the initial strength, the micro part must be fixed/held. Without sufficient adjustment/clamping it can come to a shift of the micro parts. Also existing micro adhesive bonding processes are not batch able, i.e. the individual adhesive joints of a micro system must be processed successively. In the context of the WCARP III 2006 now an innovative method is to be presented, how it is possible to solve the existing problems with micro bonding. i.e. a method is presented, which is batch able, possess a minimum joining geometry with some micrometers and is so fast that no problems with the initial strength arise. It is a method, which could revolutionize the sticking technology in the micro system engineering.