ABSTRACTS



The following is a list of the abstracts for papers which will be presented in THE FOURTH INTERNATIONAL SYMPOSIUM ON SILANES AND OTHER COUPLING AGENTS. The listing is alphabetical by presenting author. This list is updated continually to add abstracts as they become available and to make appropriate corrections. This list may be conveniently searched by using the editor provided with most popular browsers (e.g. Microsoft Explorer, Netscape, ... etc.)



Tanweer Ahsan; Research Associate, Henkel Corporation, Loctite Electronics, Olean NY 14760

Influence of the Surface Properties of Metal Leadframes on the Metal-Mold Compound Adhesion in Semiconductor Packaging



Semiconductor packaging industry demands an excellent adhesion of epoxy-based mold compounds to metal leadframes that constitute integrated circuits. Optimization of surface properties of both the metal leadframes and the mold compound is deemed essential for maximum adhesion.



Metal-epoxy adhesion is greatly affected by the surface energetics of metal leadframes. The work reports surface energies of Ni and Cu leadframes determined via contact angle method. Sequential thermal treatment and Ar-plasma cleaning, increases the surface energies of Ni metal leadframes but the adhesion to thermally treated frames is far better than the Ar-etched frames. On the other hand thermally treated copper frames provide better adhesion up to a certain level but exposure to higher temperatures, although render higher surface energies, but offer poor adhesion. It is thought that a "thin" layer of oxidized metal is beneficial to adhesion but a "thicker" layer leads to brittle and cohesive failure at the interface. It is suggested that the surface energy data alone may not predict the adhesion performance and the surface chemistry data are needed for full characterization.



Additional work shows that certain silanes in mold-compound formulations offer higher adhesive properties but only when the frame surface is thermally treated and/or Ar plasma cleaned. Surface Acoustic Microscopy (SAM) was used to probe the level of delamination at the plastic-metal interface.


Barry Arkles; Gelest, Inc., 11 East Steel Road, Morrisville, PA, 19067

Cyclic Azasilanes: Vloatile Coupling Agents for Nanotechnology



(Abstract not yet available)


R. Briard, C. Heitz and E. Barthel; Unité Mixte CNRS/Saint-Gobain, "Surface du Verre et Interface", BP 135, F-93303 Aubervilliers Cedex, FRANCE

POSTER



Glass Strengthening by Organosilane Coatings Deposited from an Aqueous Dispersion



The present general trend in glassware is for lighter products, resulting in thinner, and mechanically weaker, walls. Therefore, glass strengthening by organic coatings has become an issue [1]. In previous works, dealing with films deposited from organic solvent, it was shown that one of the key processes for strengthening by epoxy coatings is the plastic response of the film [2]. We are currently studying the strengthening properties of organosilane films deposited from an aqueous dispersion. The aim is to link the mechanical strengthening obtained by these coatings with the physico-chemical characteristics of the film and of the solution. ATR and transmission IR spectroscopy are used to monitor reactions in the dispersion (hydrolysis and condensation). Growth of the aggregates is followed by light scattering. RAIR (Reflectance Absorption InfraRed) is used to characterize chemical reactions occuring in the film during drying and thermal treatment. Hardness and Young's modulus are measured by nano-indentation. Adhesion of the film on glass is measured by DCB (Double Cantilever Beam). Finally, the efficiency of the film is tested: we measure the mechanical strength of reinforced cracks generated in a controlled manner. Further insight into the strengthening mechanism is expected from the correlation of these different approaches.



[1] - B.R. WHITTLE, J.D. WHITTLE, B. ELLIS, R.J. HAND, R.D. SHORT,The

journal of adhesion, 77-1 24, 2001. - V. VERANELAKIS, P.D. NICOLAOU, G. KORDAS, Glass Technology, Vol 41 No. 1 February 2000.



[2] J. B. Denis, "Renforcement du verre par un revêtement organique",

Doctoral Dissertation, Université Rennes I, France (2002).


Wilma Dierkes, Louis Reuvekamp, J. W. M. Noordermeer; University Twente, Faculty of Chemical Technology, Rubber Technology Group, P.O. Box 217, 7500 AE Enschede, THE NETHERLANDS

Silane Coupling Agents for Silica-filled Tire-tread Compounds: the Link Between Chemistry and Performance



Silanes are commonly used as coupling agents for silica-filled compounds in the rubber industry, mainly in tire tread compounds. The replacement of carbon black by silica results in an improvement of tire performance in terms of wet grip, abrasion resistance and rolling resistance.



The most widely used silanes are bis-(triethoxysilylpropyl)tetrasulfide (TESPT) and -disulfide (TESPD). The coupling agent firstly reacts with the silanol groups of the silica filler forming a hydrophobic shell around the filler particle and improving the compatibility between filler and polymer. Secondly the sulphur moiety is reacting with the polymer under formation of a stable network between filler and polymer.



The different steps of the formation of the filler-polymer network and their influence on the in-rubber properties are separately investigated. The silanisation efficiency of different types and numbers of alkoxygroups as well as the effect of the coupling of the polysulfide-groups to the polymer was analysed. It has been found that all functionalities have to be part of one molecule to give the well-balanced property profile that is characteristic for silica compounds.


Toru Fujii; Dept. of Mech. Eng. & Systems, Kyo-Tanabe, 610-0321, JAPAN

The Effects of Moisture and Surface Treatment on Interfacial Strength Between Epoxy Adhesive and Steel Adherend



(Abstract not yet available)


Jaspreet Singh Gandhi and Wim J. van Ooij, Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221-0012

Electrodeposition of Organofunctional Bis-Silanes on Metals



Hydrolyzed silanes are water-soluble ionized molecules so they can be deposited on metals by electrodeposition. Various combination of silane mixtures were tested at different voltages, pH, bath concentration and exposure time on panels of aluminum alloys. The surface morphology was characterized by FTIR, TOFSIMS, ellipsometry and microwave imaging. The resistance of the film to corrosion was investigated by DC polarization and electrochemical impedance spectroscopy (EIS) techniques. Electrodeposition results in a more organized and uniform film with less pores as compared to the immersed or dipped films. The layer formed at the interface between the silane and the oxide, has a very high ohmic resistance and low permeability for the electrolyte. Especially the resistance to pitting corrosion is improved by the electrodeposition process, as compared with the more common dipping process. Also, the application of a pulsed voltage led to simultaneous in situ cleaning and deposition on the samples, thus alleviating the need for the precleaning step.


J .F. Gerard, J. Galy, S. Bizet, M. Amici, H. Kaddami; IMP/Laboratoire des Matériaux Macromoléculaires, UMR CNRS 5627, Institut National des Sciences Appliquées de Lyon, Bât. Jules Verne, 69621 Villeurbanne Cedex - FRANCE

Nanocomposites from Sol-gel Chemistry of Silicon Alcoxides Vs. Introduction of Preformed Inorganic Nanoparticles (Poss Nanobuilding Blocks and Functionalized Silica)



(Abstract not yet available)


Ramsey Hamade; Department of Mechanical Engineering, American University of Beirut, 850 Third Avenue 18th floor, New York, NY 10022

Durability of Silane-modified Rubber-to-metal Adhesive Bonds



The beneficial effect of aminopropyltriethoxy-silane coupling agent when incorporated into a primer/adhesive system to bond rubber-to-metal under cathodic conditions is investigated. For durability improvement, the primer was modified by adding 6 % by weight of this silane prior to being applied to the metal substrates. The silane-modified bonded joints were found to be more resistant to weakening -a form of bond degradation- as compared with the control system for identical conditions. The concentration of the silane is correlated with reduced weakening rates.



Tests on thin free-standing films in highly alkaline NaOH solutions show that the primer reformulation resulted in enhanced hydrolysis resistance of the primer itself. Indeed, the authors showed that water uptake following exposure to alkali was inversely proportional to silane concentration.


Nobuo Ikuta; Department of Materials Science and Engineering, Shonan Institute of Technology, 1-1-25, Nishikaigan, Tsujido, Fujisawa, Kanagawa 251-8511, JAPAN

Effect of Silanes on Resin Impregnation in Rtm Molding



Effect of silane coupling agent on resin impregnation into surface modified glass fiber was examined using resin transfer molding (RTM). Glass fiber was set on a cavity in RTM , which was able to flow unsaturated polyester resin under constant pressure. The resulting glass fiber composite mold gave whitening due to micro-void around glass fiber observed from the cross-section by scanning electron microscopy. The whitening was depressed with concentration of silane coupling agent, aminopropyltriethoxysilane, for the treatment of glass fiber. In comparison, the bending modulus of the composite with silane-treated glass fiber was measured to evaluate the interfacial reinforcement by silane treatment. The critical concentration of depression of whitening was significantly lower than the minimum value of effective concentration on interfacial reinforcement. This meant that silane coupling agent gave another function different from the function of interfacial reinforcement. We call this function "resin impregnation improvement." This function was impossible to be interpreted in terms of surface wettability of resin, unlike that of water. The concept of viscoelastic shear stress of liquid resin around glass fiber was necessary to explain this function.


Eid A. Ismail; Petrochemicals Department, Egyptian Petroleum Research Institute, Nasr City, Cairo, EGYPT

WITHDRAWN



Prepatation of Thermoplastic/Thermosetting Polyurethane Adhesives Using Rosin and Modified Rosin as Chain Extenders Tackifiers



Different samples of thermoplastic and thermosetting polyurethane (PU) adhesives were prepared. The polyol used in this study was a polyester prepared by the polycondensation of 1mole phthalic anhydride with 2moles ethylene glycol to obtain a solid waxy opaque polyethylene phthalate (PEPh), MW1800. 4,4'-diphenylmethane diisocyanate was reacted with PEPh to produce isocyanate-terminated polyurethane prepolymer. The prepared prepolymer was chain extended by using ethylene glycol (EG), rosin (R) or modified rosin to produce three series of thermoplastic, thermosetting and partially thermosetting polyurethane adhesives. The modification of rosin was carried out throughout the esterification of 1mole rosin with 1mole glycerol or 1mole pentaerythritol to produce rosin-modified glycerol (RG) or rosin modified pentaerythritol (RPe) and they were characterized by IR spectra. The mechanical properties, adhesion strength and molecular weights of the prepared adhesives were determined. The molecular weight and green strength increased by increasing tackifier percent in each series. In the time, the addition of the same percent of tackifier in the three series, increased the molecular weights and green strength in the direction of RPe more than RG more than rosin. PU samples modified by rosin and RG produced thermoplastic adhesives, while the samples modified by RPe (3.31-6.92)% produced thermosetting adhesives and that modified by RPe 1.26% give partially thermosetting adhesive. The thermosetting samples are infusible and insoluble in organic solvents.


F.R. Jones1 and V Cech2

1) Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building Mappin Street, Sheffield, S1 3JD, UK



2) Institute of Materials Chemistry, Brno University of Technology, Purknova 118, Brno, CZECH REPUBLIC



Thin Films from Vinyl Triethoxysilane Prepared by Plasma Polymerisation and Aqueous Solution



Glass fibres are traditionally surface coated with aqueous based silane coupling agents. Plasma polymerisation has been used to deposit thin conformal films from the gas phase. The structure and mechanical properties of these 'silane' films have been compared. For the former FTIR, XPS have been used extensively whereas nanoindentation has been used to assess the modulus of the deposits.



This paper will show how the plasma technique can be used to control the properties of the coatings more efficiently.


D.J. Marks and F.R. Jones; Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building Mappin Street, Sheffield, S1 3JD UK

Plasma Polymerised Coatings for Adhesion Promotion in Fibre Composites



The paper will review the use of plasma polymers for adhesion promotion and present the results of a study of their application to glass fibres. Uncoupled unsized glass fibres were subjected to a continuous treatment to coat the tows with an Acrylic Acid / Octadiene plasma copolymer. The fibres were separated prior to coating in order to minimise shadowing effects associated with the coating of fibre bundles. The plasma polymer coating was analysed for composition and coating uniformity using high resolution XPS which confirmed that increasing Acrylic Acid content in the plasma copolymer led to an increase in retained surface Carboxylic Acid groups (confirmed by Trifluoroethanol derivatisation). The single filament strengths of the coated and uncoated, separated control fibres were comparable. However, for the plasma polymer coated fibres, there was less variability (assessed using Weibull modulus), in comparison to the separated unsized fibres. Single fibre fragmentation testing was used to identify the change in the interfacial response as a function of the fibre coating. A functionalised plasma polymer with high acrylic acid content gave rise to a strong interfacial bond, with little debonding. The unfunctionalised Octadiene plasma polymer coated fibres, exhibited a poor interfacial strength, with significant levels of debonding. It is concluded that glass fibre tows can be continuously coated with plasma copolymers, leading to uniform levels of coating throughout the fibre tow, thus giving the ability to tailor the interfacial response of the composite.


Stephen L. Kaplan; 4th State Inc., 1260 Elmer Street, Belmont, CA 94002-2806

Cold Gas Plasma and Silanes

For many decades silane coupling agents have dominated as the chemistry of choice to significantly enhance adhesive bonding between different materials. In the past two or three decades cold gas plasma has become a viable contender as the preferred means of treating materials to enhance adhesion. What happens if these two potent methods work in concert? This paper will present data on the use of plasma processes employing silanes to promote adhesion.


Amir Ershad Langroudi; Faculty of Processing, Iran Polymer and Petrochemical Institute, P.O.Box 14965/115, Tehran, IRAN

Synthesis and Characterization of Nanocomposite Hybrid Coatings via In Situ Sol-Gel Reactions



A series of hybrid nanocomposites have been prepared by undergoing partial free radical copolymerization of methyl methacrylate and alkoxysilane-methacrylate at several feeds. The partial copolymer precursors were then hydrolyzed and condensed during the simultaneous in situ growing of the silica phase through the acid catalyzed sol-gel polymerization of tetramethylorthosilicate.



The hybrids were characterized by different techniques. The hybrid coating system was applied on copper plate and soda glass pieces. The experimental results show the coating film has good qualities like optical transparency, excellent adhesion to the substrates and nanoscale phase separation. The hydrophobic behavior of hybrid was increased by adding different fluorinated precursors to the system. The hydrophobicity of coating system depends to the long of chain in the surface modifier precursors. By increasing of long of fluorinated chain in the precursors, the hydrophobicity of coating increases up to 105 and the free surface of energy decreases to about 15mJ/m2. In addition, experimental results show that hydrophobicity of coating is not influenced by the substrates.


Wim Laureyn; IMEC, MCP-BIO, Kapeldreef 75, B-3001 Heverlee, BELGIUM

Biosensor Interfaces Based on Functionalised Self-assembled Monolayers of Trichlorosilanes



(Abstract not yet available) WITHDRAWN


H. Barthel1, T. Gottschalk1, and M. Lucarelli2

1) Wacker-Chemie GmbH, Werk Burghausen, D-84489 Burghausen, GERMANY

2) Wacker Chemical Corporation, 3301 Sutton Road, Adrain, MI 49221-9397



Organofunctional Pyrogenic Silica as a Reactive Reinforcing Filler for Polymers



Reinforcing fillers have been used in thermosetting polymers as a means of improving mechanical propeties. The incorporation of the proper filler can significantly improve properties such as transparency, scratch resistance and heat resistance as well as others. This session will deal with the use of organofunctional pyrogenic silica as a filler capable of chemically bonding into the polymer network, resulting in the improvement of the mechanical strength of various polymers. The aim of the paper will be primarily focused on the functionalizing of the silica as well as the impact of these silicas on the rheological and mechanical properties of the polymers, such as epoxies, polyurethanes and silicones.



POSTER


Helmut Mack; DEGUSSA AG, AS-FA-SL, Untere Kanalstrasse 3, D-79618 Rheinfelden, GERMANY

Silane Oligomers: A Class of Their Own



Monomeric organofunctional silanes, e.g. R-(CH(subscript: 2))(subscript: 3) -Si(OR')(subscript: 3) (R = organofunctional group, R' = acyloxy, alkoxide) have been used as adhesion promoters for many years. More recently, oligomeric silanes have been commercialized and their value in improving adhesion has been investigated. Of particular interest is the improvement in silane film-formation on substrates which results from their use. In addition, oligomeric silanes offer outstanding physical properties such as low volatility, low viscosity, and reduced volatile organic compounds to the user. Moreover, a chemical multifunctionality can be realized within one silane product. Product processability and safety (e.g. high flash point) is excellent. The superior performance of oligomeric silanes over commonly used monomeric silanes will be illustrated by (superscript: 29)Si NMR (nuclear resonance spectroscopy) and AES (Auger electron spectroscopoy) data.


J. P. Matinlinna, K. Laajalehto, A. Yli-urpo, L. V. J. Lassila and P. K. Vallittu; University of Turku, Department of Prosthetic Dentistry and Biomaterials Research, FIN-20520 Turku, FINLAND

FTIR and XPS Surface Characterization of Allyltrimethoxysilane and 3-Methacryloxypropyltrimethoxysilane Mixture Treated Titanium Substrate



3-methacryloxypropyltrimethoxysilane (MPS) is widely used to enhance bonding metals and ceramics to composite resins in dentistry. The aim of this study was to estimate adhesion promoting siloxane film formation on titanium. Very recent theory suggests that silane mixtures may show good performance. MPS and ALS (allyltrimethoxysilane) together could form a stable, interpenetrating network layer with titanium.



Titanium substrates were wet ground (1200 grit), rinsed with de-ionised water, and degreased ultrasonically with ethanol and acetone. Silane mixtures applied were 0.25% ALS + 0.25 MPS, and 0.5% ALS + 0.5% MPS, both in 95% wt-% 2-propanol. The pH was adjusted to 4.5 and 1 h was allowed for the hydrolysis.



Titanium substrates were silanated and the hydrolysation and condensation were followed at room temperature (RT) for 15 min. Another group of samples were silanated and cured for 1 h at 110 C. Surface analysis was performed with ATR- (attenuated total reflectance infrared spectroscopy), RA-FTIR (reflectance-absorbance Fourier transform infrared spectroscopy), and XPS (X-ray photoelectron spectroscopy) techniques.



The XPS analysis indicated a uniform layer of covalent siloxane bonds (-Si-O-Si) and Ti-O-Si bonds on the titanium surface. All FTIR signals for these bonds were essentially stronger in heat cured samples, suggesting a more complete polycondensation of siloxane network than obtained at RT. Water storage in 37 C for 24 h did not deteriorate the surface. These results could influence the stability of silane promoted adhesion in a moist environment.


Carosena Meola1 and Giuseppe Giorleo2

1) DETEC - Università di Napoli "Federico II", P.le Tecchio 80, 80125 Napoli, ITALY

2) DIMP - Università di Napoli "Federico II", P.le Tecchio 80, 80125 Napoli, ITALY



Role of Polymer Surface Modifiction in Adhesively Bonded Joints: Analysis and Testing



(Abstract not yet available)


Anthony A. Parker; A. A. Parker Consulting, Newtown, PA 18940

Keeping the Music Alive with Surface Chemistry: Musical Instrument Strings and Corrosion

The corrosion resistance of musical instrument strings can be improved by minimizing the galvanic couple between the winding and core metals, where the best corrosion resistance is achieved when the metals are galvanically equivalent. Corrosion resistance can also be improved through the use of appropriate metal surface treatments. For the case of phosphor-bronze wound strings, corrosion resistance is improved when the surface is modified with azole compounds such as benzotriazole and benzimidazole. Corrosion resistance is also improved when the surface is modified with N-2-aminoethyl-3-aminopropyltrimethoxysilane(AAPS). These improvements are most noteworthy when the core of the string is more cathodic in character (i.e.,titanium as opposed to steel). The corrosion inhibiting function of benzotriazole and other azole compounds is known to result from a combination of factors including the ability of the azole functionality to chelate with the metal oxide surface to form an oxide-reinforcing polymer network. Unlike other comparative compounds, AAPS possesses analogous molecular-level capabilities, and also provides improved corrosion protection. Collectively, these results provide unique insight into the common molecular level attributes of good corrosion inhibitors.


Vignesh Palanivel and W.J. van Ooij, Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221-0012, USA

Modified Silane Films as an Alternative to Chromates for Corrosion Protection of AA2024-T3 Alloys



Silane coatings on the aluminum aerospace alloy AA2024-T3 have been proposed as an alternative to chromate conversion coatings for surface pretreatment. The corrosion protection offered by these silane films is comparable to chromates and in certain cases even better. However, the silane coatings are not visible and do not posses the "self-healing" capability that chromates are known for. In this paper we show that silane films can be colored and that a self-healing effect can be achieved by adding optimum amounts of leachable inhibitors to the silane film which can be released at a controlled rate. We have studied the corrosion properties of colored silane films and have shown that the corrosion inhibition property of the silane film is not affected adversely. Additionally, loading of a small amount of nanoparticles such as silica into the silane film can strengthen and enhance the corrosion protection of silanes on AA2024-T3 alloys further. Two different silane systems were studied, viz., a solvent-based system and a completely water-based system.


E. R. Pohl and A. Chaves; Crompton Corporation, OSi Specialties, 771 Old Saw Mill River Road, Tarrytown, NY 10591

Hydrolysis of Sterically Hindered Alkoxysilanes



Alkoxysilanes with sterically hindered alkoxy groups have been used in one-component waterborne formulations with long-term shelf stability. Vinyltrialkoxysilanes were used to investigate the effects of the leaving group on the rates of silane hydrolysis. The acid and base-catalyzed rates of hydrolysis for these silanes were measured under pseudo-first order conditions in an aqueous acetone solution. Steric and polar characteristics of the alkoxy leaving group affect the hydrolysis rates. Taft equations were constructed by using the rate constants and redefined substituent constants.


Rex D. Ramsier; Departments of Physics, Chemistry, and Chemical Engineering, The University of Akron, 250 Buchtel Commons, Ayer Hall 111

Akron, OH 44325-4001



Adsorption of Organo-Phosphorus Species on Oxidized Metal Surfaces



Adsorption of Organo-Phosphorus Species on Oxidized Metal SurfacesAluminum, titanium and zirconium alloys play a major role in industrial applications where corrosion resistance is a primary safety concern. We are studying the adsorption of thin films of hydrogenated and fluorinated phosphorus-acids on oxidized aluminum, titanium and zirconium surfaces to investigate their potential as corrosion inhibiting coatings, adhesion promoters, or anti-stiction modifiers. Our goals are to determine (1) the surface reaction mechanisms, (2) the role of the film deposition method, and (3) the resulting environmental stability of the films. Combining surface infrared spectroscopy with solid state nuclear magnetic resonance and other techniques we are able to elucidate the controlling factors in film deposition and subsequent behavior. For example, on aluminum, local sonication during deposition strongly enhances the surface coverage and durability of certain fluorinated thin films but does not improve films made from hydrogenated species. Similarly, thermal pre-processing of Zircaloy-2 strongly affects its subsequent reactivity toward many organo-phosphorus compounds. In this presentation we summarize our findings and relate these to relevant technologies.


Michael S. Kent,1 Guirong Pan,2 Jarek Majewski,3 and Dale W. Schaefer2



1) Sandia Nation Laboratories, Albuquerque, NM 87115



2) Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221



3) Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, NM 87585



Swelling of Silane Water-Barrier Films



Neutron reflectivity is an effective tool to examine the swelling and degradation of silane water-barrier films. Sub micron films of bis(triethoxysilyl)ethane (BTSE) and bis(triethoxy)aminopropane (BTSA) were examined in the dry state and in the presence of deuterated water and nitrobenzene vapor. Deuteration provides excellent neutron contrast with the silane. BTSE does not swell in either vapor, consistent with a high crosslink density as expected from its chemical structure. On the other hand, at room temperature BTSA swells substantially in both water and nitrobenzene, consistent with lower crosslink density, enhanced hydrophilicity, and reduced water barrier properties.

Degradation of the films was induced by exposure to water at 80 C. The swelling behavior of BTSE was unaffected by conditioning at 80 C, suggesting little or no degradation or chemical changes. The BTSA films, on the other hand, showed irreversible changes in the network structure, evidenced by reduced swelling after conditioning.

By modeling the reflectivity data it is possible to map the swelling profiles. The results indicate that the swelling is greater near the air surface, consistent with a gradient in the crosslink density of the films.


Eckhard Schollmeyer, Torsten Textor, Dierk Knittel, Thomas Bahners

Deutsches Textilforschungszentrum Nord-West e.V. D-47798 Krefeld, GERMANY



Coating of Textile Fibres with Organic-inorganic Hybrid Polymers



Increasing demands for specialised textiles, above all technical textiles as high performance products can be observed world-wide. Therefore intensive research work is done for finding new methods that lead to well-aimed modification or functionalisation techniques for (synthetic) fibre surfaces yielding in improved or even new properties. Innovative methods for textile finishing are the coating of fibre material with organic-inorganic hybrid polymers following the sol-gel process or the employment of excimer-UV-light sources to create certain surface properties.



In modern material development ceramic materials, primarily the application of thin ceramic layers offer far-reaching possibilities for permanent surface modifications. In this context coatings based on organically modified ceramics (organic-inorganic hybrid polymers) as known from other materials, have an immense potential for creative modifications of surface properties with a comparatively low technical effort at moderate temperatures.



Excimer-UV-sources allow to achieve various interesting surface modifications. Photo-chemical surface grafting reaction can be carried out, making use of the monochromatic radiation emitted by excimer-UV-lamps. The graftings can e.g. lead to very hydrophobic/oleophobic or hydrophilic surfaces but the approach can also solve certain adhesion problems. Using excimer-UV-lasers polymer surfaces can be physically modified without significant photo-chemical modifications. These modifications change the surface structure of films or fibres, leading to a micro-structured topography.


Anuj Seth and Wim J. van Ooij; Department of Chemical And Materials, Engineering , University of Cincinnati, Cincinnati, OH 45221-0012

Silane Coupling Agents For Prevention of Corrosion Fatigue Cracking of Aerospace Alloys AA2024-T3 AND AA7075-T6



Currently used chromate pretreatment used for aerospace alloys to prevent corrosion and corrosion fatigue cracking contain Cr(VI) ions which results in health hazards associated with the current process. Thus these chromate conversion coatings have been subjected to restrictions. Silane coupling agents have been found to provide excellent corrosion inhibition, economic competitiveness, and possess environmental compatibility. They can be regarded as prospective replacements for the chromating technology. In this work, an investigation has been carried out using a probabilistic model for the efficiency with which bis-type silanes such as bis-amino, bis-sulfur silane, bis-ureido silane, tris-silanes, and a combination of these, can be used to prevent corrosion fatigue cracking of AA2024-T3 and AA7075-T6 alloys. The model consists of loading dog-bone specimens at 65% of their calculated UTS for an AA7075-T6 alloy and at 70% UTS for an AA2024-T3 alloy. The dog-bones are loaded and alternated with exposure to salt spray conditions. This cycle of fatigue loading and salt spray continues until the sample breaks. Control specimens are chromated and uncoated samples. It is observed that most silanes result in a corrosion fatigue life which is greater than that observed for the chromated control samples for both alloys. A model will be presented and discussed.


A. N. N. Adams1, A. J. Kinloch1 and S. J. Shaw 2

1) Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, University of London UK

2) Future Systems Technology Division, QinetiQ, Farnborough UK



The Influence of Organosilane Surface Treatments on the Durability and Cyclic Fatigue Characteristics of Bonded Aluminium Alloy Joints



In order to promote adequate long-term durability in bonded aluminium structures, the alloy must usually be subjected to surface treatment prior to application of the adhesive and bonding. For bonded aerospace structures, surface treatments comprising CrVI compounds have traditionally been used. However, in recent years there has been growing pressure from government and environmental bodies to remove such substances from manufacturing processes. With these concerns in mind, considerable effort in numerous laboratories has been directed toward the development of relatively benign alternatives to the CrVI based systems. Much of this effort has focused on organosilanes.



Recent effort within the authors laboratories has contributed to an international project designed to both explore the optimum methods of silane application and the mechanisms responsible for the improved durability performance obtained. In this paper we present the results obtained from several aspects of this work.



First, the various solution parameters appropriate for enhanced joint durability are discussed with reference to 'simple' durability assessment based upon Boeing wedge joints. Results obtained to assess the influence of parameters such as the nature of the solvent employed with silane solutions, together with silane concentration and film drying conditions, are discussed. In addition, the effects of cyclic fatigue loading on tapered double cantilever beam joints prepared from substrates previously pre-treated from an optimised silane solution are considered. The improvements in performance provided by this treatment, with particular emphasis on Gmax - da/dN and fatigue threshold characteristics are discussed, together with observations on the failure mechanisms prevailing under the experimental conditions studied.


Matthew B. Stacy and Wim J. van Ooij; Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221-0012

Rubber-Metal Bonding by Organofunctional Silanes

This study deals with the bonding of sulfur-vulcanized rubber compounds to metals using a silane technology. Brass alloys, plated brass on steel, and electrogalvanized steel surfaces were all bonded to typical tire cord NR rubber compounds with and without cobalt adhesion promoters.

Previous experiments have reported excellent adhesion results using deposited non-hydrolyzed mixtures of bis-(trimethoxysilylpropyl)amine and bis-(triethoxysilypropyl)tetrasulfide. While these silane mixtures also demonstrated excellent corrosion resistance, efforts have continued to identify other adhesives without resorting to neat applications, but rather using submicron thin films resulting from hydrolyzed silane solution application. This paper details the positive results of rubber peel tests using hydrolyzed silanes and discusses both the structure of hydrolyzed silane films on metal substrates and possible explanations for the poor results previously reported using such hydrolyzed materials as rubber-to-metal adhesives.


B. G. Tilset, F. Lapique, A. Bjørgum and C. J. Simensen

SINTEF Materials Technology, P.O.Box 124 Blindern, N-0314 Oslo, NORWAY



BTSE and g-APS Pre-treatments for Adhesive Bonding of Aluminium



Use of aluminium is increasing within the car industry. For this material, structural adhesive bonding is being investigated as an alternative to e.g. riveting and welding. Pre-treatments are necessary and most of the current ones involve the use of hexavalent chromium. For environmental reasons, alternatives must be found and silanisation is one possibility.

In the present study, monomolecular layers of g-aminopropylsilane (g-APS) and bis(triethoxy)silylethane (BTSE) were used alone or in combination as pre-treatments for adhesive bonding of aluminium with epoxy adhesives.

Introductory studies showed that BTSE used alone was most efficient. It was speculated that BTSE reinforced the adhesive bond by interacting with the silanes present in the adhesive. To test this hypothesis, samples were bonded using silane-containing and silane-free adhesives. Samples were subjected to wedge tests, acetic acid salt spray tests and surface analysis. The results suggest that BTSE improves the durability of adhesive bonds by decreasing the hydrolysis and/or corrosion rate at the metal -adhesive interface. g-APS, on the other hand, increases the original strength of the adhesive bond by interacting chemically with the adhesive.

Currently, attempts are made to combine chemical bonding and corrosion protection. Results from these studies will also be presented.


N. H. Tung, Y. Inagaki, T. Fujii, K. Okubo; Doshisha University, Dept. of Mech. Engineering, Kyo-Tanabe, Kyoto 610-0321, JAPAN

Interfacial Adhesion Improvement of Bamboo Fiber and Polypropylene (PP) in Bamboo-PP Composite



Recently, bamboo-PP composite (BFPP) has been much attention. However, its strength is not enough for many applications. The poor interfacial strength between bamboo fiber and PP matrix arises, and lead to the low strength of the composites. To improve the interfacial strength, the bamboo fiber surface was treated by coupling agent. Three kinds of coupling agents (isocyanate, amino and methacryloxy silane) were used in this study.

After treatment, the coupling agents have multiply strong and stable bonds with the bamboo surface. The observed content of bamboo fibers in BFPP can be increased while the strength slightly decreases. The modulus of BFPP also increased due to isocyanate silane treatment. Isocyanate silane is the best coupling agent in three kinds of silane for BFPP.


Wim J. van Ooij, Vignesh Palanivel, Danqing Zhu, Matt Stacy, Anna Lamar and Anuj Seth; Department of Chemical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221-0012

Overview of Mechanisms of Corrosion Protection of Metals by Silane Films



Researchers at the University of Cincinnati have been engaged in the development of novel corrosion-inhibiting metal pretreatments since 1994. Such treatments are based on the use of silane coupling agents, especially the so-called bis-silanes which have been shown to be considerably more potent than the mono-silanes. The main application of such treatments is to replace chromate and phosphate pretreatments in a wide range of metal-finishing industries. In this paper an overview is given of the state of our research with emphasis on the mechanisms by which films of silane coupling agents prevent many forms of corrosion, both uniform and localized, in metals such as steel, stainless steel, aluminum alloys and magnesium. It will be shown that mixtures of silanes often have synergistic properties as compared with the individual silanes. Recently we have shown that thin silane films can be modified by additions such as small particles, dyes, fibers and leachable chemicals. This 'reservoir' function of silanes has opened up a whole new range of possible applications. Some of those will be discussed.


Petri Widsten and Jaakko E. Laine; Laboratory of Paper Technology, Dept. of Forest Products Techology, Helsinki University of Technology, P.O.Box 6300, FIN-02015 HUT, FINLAND

Manufacture of Resin-Free Fiberboard from Wood Fibers Activated by Treatment with Fenton's Reagent



Abstract - High-temperature defibration of wood at preheating temperatures of 171-202C generated low-molecular weight, water-soluble lignin fragments in the fibers. The lignin is characterized by a high content of phenolic hydroxyl groups and a low content of interunit -aryl ether linkages. When treated with hydrogen peroxide in the presence of a decomposition catalyst (Fenton's reagent), phenoxy radicals were formed in the lignin, presumably by the action of oxygen-based radicals formed as peroxide decomposition products. Dry-process fiberboards with densities in the hardboard range (> 0.9 g/cm3) of high mechanical strength were made from softwood or hardwood fibers treated with Fenton's reagent (H2O2/FeSO4) in the refiner blowline without synthetic resins. The adhesion effect is believed to be largely associated with interaction of phenoxy radicals on adjacent fibers, resulting in interfiber covalent bonding. The internal bond strength (IB) and other mechanical properties of the boards improved with an increase in defibration temperature, whereas board thickness swell was mainly dependent on the amount of sizing agent or other additives used. Differences in the lignin/carbohydrate distribution of fiber surfaces did not account for the different fiber reactivities observed during oxidation with Fenton's reagent.