Adhesion science and engineering volume 2, the mechanics of adhesion surfaces, chemistry applicat

ADHESION SCIENCE URFACES, CHEMISTRY PLICATIONS Edited by M. Chaudhary and AX Fb&s ADHESION SCIENCE AND ENGINEERING - 2 Series Editor A.V. Pocius The cover displays a micrograph of glass particles on a plasticized polystyrene substrate showing adhesion-induced viscous flow of the substrate and encapsulation of the particle. The crater is the deformed substrate after a particle had been removed. The micrograph was taken by Ray Bowen and was supplied by Dr. Donald Rimai. ADHESION SCIENCE AND ENGINEERING - 2 SURFACES, CHEMISTRY AND APPLICATIONS Edited by M. Chaudhury Department of Chemical Engineering Center for Polymer Inter$aces Leh igh University 111 Research Drive Bethlehem, PA I81 05 U.S.A. A.V. Pocius 3M Adhesive Technologies Center 3M Centei; Building 201 -4N-01 St. Paul, MN 55144-1000 U.S.A. 2002 ELSEVIER Amsterdam - Boston - London - New York - Oxford - Paris - San Diego San Francisco - Singapore - Sydney - Tokyo ELSEVIER SCIENCE B.V. Sara Burgerhartstraat 25 P.O. 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British Library Cataloguing in Publication Data A catalogue record from the British Library has been applied for. ISBN: 0 444 5 1140 7 (set) 8 The paper used in this publication meets the requirements of ANSUNISO Printed in The Netherlands. Preface Volume I of Adhesion Science and Engineering dealt with the mechanics of adhesive bonds and the rheology of adhesives. Volume I1 deals with the other two disciplines that make up adhesion science, surfaces and chemistry. In addition, this volume describes several applications of adhesion science and engineering. The volume begins with discussions of aspects of surface science and how they relate to adhesion science. Methods based on surface thermodynamics have been powerful tools in the hands of adhesion scientists. Berg introduces us to the topics of interfacial thermodynamic and practical adhesion and shows how the critical predictive parameters of adhesion can be obtained from wetting, solution theory and group contribution methods (UNIFAC). It becomes clear from Berg’s presentation that the predictions of adhesion strengths by the traditional wet chemical methods are somewhat empirical. This limitation can be partially overcome by the methods of contact mechanics as pioneered by Johnson, Kendall and Roberts, which allows direct measurements of the surface energies of deformable solids. These methods, as shown by Mangipudi and Falsafi, have played a very important role in developing a deeper understanding of the relationship between adhesion and the chemical composition of surfaces and complement the chapters describing contact mechanics found in Volume I. Rimai and Quesnel extend this discussion to the interaction of powdered solids and give us an in-depth view of the types of intermolecular forces that control adhesion of solid surfaces. The chapter by Wahl and Syed Asif explores the behavior of adhesion and contact mechanics at the nanoscopic level. This chapter not only complements the above three but also describes additional techniques that may be used to probe the properties of surfaces. Surface roughness, which could be examined by some of the probe techniques described in Chapter 4, is discussed by Packham. Spectroscopic techniques useful for examination of the chemistry of surface and interfaces are described by Boerio (Chapter 6). Other aspects of interfacial science and chemistry are examined by Owen and Wool. The former chapter deals with a widely used chemistry to join disparate sur- faces, that of silane coupling agents. The latter chapter describes the phenomenon of diffusion at interfaces, which, when it occurs, can yield strong and durable adhesive bonds. Brown’s chapter describes the micromechanics at the interface when certain types of diffusive adhesive bonds are broken. The section on surfaces ends with Dillingham’s discussion of what can be done to prime surfaces for adhesive bonding. The section on chemistry of adhesives evolves from rubber-based adhesives to semi- structural and finally to structural adhesives. Everaerts and Clemens provide a thorough description of chemistry and applications of pressure sensitive adhe- sives and Kinning and Schneider describe an enabling technology for pressure vi Preface sensitive adhesive tapes, release coatings. Martin-Martinez reviews the chemistry and physical properties of rubber-based adhesives with an emphasis on the mate- rials properties of the components of those adhesives. Silicone chemistry provides products that range from pressure sensitive adhesives to sealants to semi-structural adhesives and is described by Parbhoo et al. in Chapter 14. Progressing into more semi-structural and structural adhesives, the chapters by Paul and by Frisch describe the chemistry and properties of hot melt adhesives and polyurethane ad- hesives, respectively. The remainder of this section deals with structural adhesives beginning with discussions of acrylate chemistry by Righettini and then Klemar- czyk. The adhesives described in these two chapters are some of the most easy to use structural adhesives available. One of the oldest technologies in modern adhesive chemistry, phenolic chemistry is described by Detlefson and one of the newer chemistries, bismaleimides is discussed by Kajiyama. The final section in this volume deals with applications of adhesion science. The applications described include methods by which durable adhesive bonds can be manufactured by the use of appropriate surface preparation (Davis and Venables) to unique methods for composite repair (Lopata et al.) Adhesive applications find their way into the generation of wood products (Dunky and Pizzi) and also find their way into the construction of commercial and military aircraft (Pate). The chapter by Spotnitz et al. shows that adhesion science finds its way into the life sciences in their discussion of tissue adhesives. The editors wish to express their sincere thanks to the contributing authors for their invaluable contributions to this volume. Their collective expertise represents many years of industrial and academic experience in the field of Adhesion Sci- ence and Engineering. We would also like to thank the employers of each of the contributors for allowing them to take on the extra tasks associated with the com- pletion of their contribution to this volume. We would also like to acknowledge the contribution of Mr. Theodore Reinhart of the University of Dayton Research Center to the initial organization of this volume. An unfortunate illness prevented him from completing his work on this project. Assistance from the Department of Chemical Engineering and the NSF sponsored IUCRC of the Polymer Interface Center at Lehigh University are gratefully acknowledged. Finally, we thank our spouses for their patience as we compiled and edited this volume. ALPHONSUS V. POCIUS Editor Corporate Scientisl 3M Company St. Paul, MN, USA MANOJ CHAUDHURY Associate Editor Professor of Chemical Engineering Directol; Center for Polymer Interjkes Lehigh University Bethlehem, PA, USA Contents Preface v Surface Science Chapter 1. Semi-empirical strategies for predicting adhesion J.C. Berg 1 Chapter 2. Direct estimation of the adhesion of solid polymers KS, Mangipudi and A. Faha$. 75 Chapter 3. Particle adhesion D.S. Rimai and D.J. Quesnel 139 Chapter 4. Surface mechanical measurements at the nanoscale K.J. Wahl and SA. Syed Asif. 193 Chapter 5. Micro-mechanical processes in adhesion and fracture H.R. Brown 221 Chapter 6. Surface analysis in adhesion science EJ. Boerio 243 Chapter 7. Surface roughness and adhesion D. E. Packham. 3 17 Chapter 8. Diffusion and autohesion R.P. Wool 351 Chapter 9. Coupling agents: chemical bonding at interfaces M.J. Owen 403 Chapter 10. Priming to improve adhesion G. Uillingham 433 [...]... for the molten resins against the fibers This study showed the direct relationship between the mechanical properties and the void morphology within the laminates after consolidation In seeking to minimize the contact angle or to promote wetting of the adherend by the adhesive, one must consider the effects both of the chemistry of the components and of the morphology of the adherend surface on the. .. or swell the solid The extrapolated value of the surface tension on the Zisman plot has the practical significance of being the surface tension of a liquid at or below which the solid will be wet out Zisman noted that the value of yc was independent of the liquids used and was therefore characteristic of the solid alone He designated it as the ‘critical surface tension’ of the solid, yc, and regarded... on the dynamics of the wetting process and the factors upon which it depends 1.4.2 The relationship between wetting and solid sugace energy The effect of the chemical makeup of the adhesive/adherend system on contact angle and wetting is manifest through the influence of such chemistry on the surface free energies of the adhesive-air (or other fluid medium), adherend-air J.C Berg 20 1 (c) Fig 9 The. .. number of successful interpretations of fiber fragmentation tests on these types of systems described later The most-often cited theoretical underpinning for a relationship between practical adhesion energy and the work of adhesion is the generalized fracture mechanics theory of Gent and coworkers [23-251 and contributed to by Andrews and Kinloch [26-291 This defines a linear relationship between the. .. interdigitation of the materials, or they may be simply the result of structuring of the adhesive layer adjacent to the interface due to the asymmetric molecular forces existing at the boundary between the phases Such an ‘interphase’ has a structure, and possibly a composition, distinct from that of either of the bulk phases Recognizing the ubiquitous presence of interphases, the following definition of terms... mechanical work of separation, w,, and the thermodynamic work of adhesion: = C(b,T,&)’wA, (8) where w, is the work of separation (per unit area) and C is the mechanical loss factor, which accounts for the effects of geometry and rheology, and depends on wm Semi-empirical strategies for predicting adhesion 11 the crack growth rate (a), temperature ( T ) and maximum strain level ( E ) The theory was developed... ‘contact adhesion Because of the rather short-range nature of molecular interactions, they occur principally between the outermost molecular layers of the adherend and the molecules of the adhesive immediately adjacent to them and are said to be ‘adsorbed’ to the adherend surface Such adsorption may be purely physical (physisorption), or it may involve the formation of covalent bonds across the interface... correlations between interfacial forces and ‘interfacial strength’ The two issues that are dominant in determining the interfacial strength in the case of contact adhesion are: (1) the completeness and intimacy of contact between the adhesive and adherend at the interface; and (2) the strength of the intermolecular interactions across the interface Methods for predicting both of these factors are discussed below... aside from its effect on the work of adhesion In an experiment involving epoxy resin and polyethylene, they found the adhesion to be poor when liquid (uncured) epoxy resin was deposited as an adhesive on the polyethylene substrate On the other hand, if the epoxy was first cured, and then molten polyethylene were applied to it as the adhesive, the adhesion was excellent Since the same interface was created... mechanism (difusion interphase adhesion) A situation distinct from contact adhesion described above often arises in the bonding of polymeric adherends and adhesives, in particular in the bonding of specimens of the same polymer together (autoadhesion) In such cases, if there is adequate thermodynamic compatibility (in the sense of mutual solubility) between the polymers, the polymer molecules are mobile . (set) 8 The paper used in this publication meets the requirements of ANSUNISO Printed in The Netherlands. Preface Volume I of Adhesion Science and Engineering dealt with the mechanics of adhesive. applications of adhesion science and engineering. The volume begins with discussions of aspects of surface science and how they relate to adhesion science. Methods based on surface thermodynamics. tools in the hands of adhesion scientists. Berg introduces us to the topics of interfacial thermodynamic and practical adhesion and shows how the critical predictive parameters of adhesion