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Second international conference on speciality hot melts
considered as an anticipation of future problems. The participants of the conference were informed on the behaviour of composite materials under impact-like load conditions that may occur by hail, birds, screws and stones whirled up from the runway or by improper handling. In this context, too, the question arose as to what extent composite structures, like metal structures, 'forgive' minor damage and under what conditions failure of the component part has to be taken into account. In general the impression dominated that current testing procedures (essentially NDT) are not satisfactorily reliable for advanced recognition of damage or for the localization of damaged areas. An active interest also met statements concerning the protection of composites from the consequences of lightning, and the effects of the shock wave and thermal loadings on the structure. Possibilities for a remedy besides those by design changes were pointed out. Participants were also reminded that after a repair the flow of current through the component part has to be guaranteed. In a remarkable contribution on structural materials for future aircraft generations, it was stated that, in addition to increased safety for aircraft and passengers, reductions of the structural weight and manufacturing cost will be the highest priorities. From this point of
view, large-scale use of aluminium/lithium alloys at least seems to be doubtful. On the other hand, the application of carbon fibre-reinforced plastics (CFRP), especially as CFRP/honeycomb sandwich structures, will also be extended to primary structural parts. As a result, in addition to a substantial weight reduction, increased fire protection against the penetration of the flames or collapse of the structure will be achieved compared with metal structures. Furthermore, a great potential for economy in manufacturing costs, utilized inadequately to date, may be exploited by the use of advanced manufacturing techniques and adequate materials, such as superplastic materials. The meeting concluded with a final discussion of the participants together with the readers of the papers under the chairmanship of Dr Brockmann. Afterwards there was a chance to vist the repair shop of Deutsche Lufthansa in Hamburg; most of the participants of the meeting made use of this opportunity. The participants of the BASTART 87 workshop agreed that the meeting was useful for an improved information exchange and hence should be continued.
14. Schafer I~ Wolitz
Second International Conference on Speciality Hot Melts Penta Hotel, Heathrow, UK, 14-1 5 May 1987
Organized by: Dermil Research Limited Dermil Research Limited achieved an attendance of something over two hundred, drawn from at least eight different countries, during their Second International Conference on Speciality Hot Melts. During the two days of the meeting, twenty-two separate papers were given, of which only two were from the organizers. Before plunging into the details of any particular type of adhesive or the intricacies of specific applications, Dr John C o m y n of Leicester Polytechnic laid the foundation with a lucid but concise account of the fundamentals of the whole concept of hot-melt adhesives. This was augmented by a discussion of contributions to adhesive properties by the introduction of functional and polar groups into an EVA copolymer adhesive from the groups at Mulhouse and delivered by M.P. Borg. Then followed a series of papers which fell into two groups (although these were distributed through the two days.) One group dealt with detailed chemistry and uses of individual types of adhesives and their most recent developments. The other group considered areas of industry where hot-melt adhesives have a significant role, and how these roles were (or were not) being played satisfactorily. If I am not to weary my readers beyond endurance it is impossible to consider each of these papers in any detail, so I must select. The choice
218
INT.J.ADHESIONAND ADHESIVES OCTOBER 1987
must be idiosyncratic but I hope will be without prejudice. A dual act by Mr Godfrey and Dr Cooray presented an account of their development of a range of urethane-acrylic prepolymers which are applied by hot-melt techniques but which then cross-link by a second heating. This seems to present some novel features and attracted attention. An alternative system, described by Mr C.M. Allen, was based on a polyurethane prepolymer which is applied as a melt at 60-100°C and then cured by reaction with atmospheric moisture. This clearly implies that there is some time during which the full strength is increasing; with leather this can be as short as 5-8 hours although with metal substrates it may be several days. Another group of more recently developed hot-melt adhesives is being produced from polyamide derivatives of dimerized, unsaturated long-chain carboxylic acids derived from natural fats and oils as described by Dr J. Wichelhaus. Then there were accounts of copolyester (dimethyl terephthalate) resins and of copolymers of ethylene with maleic anhydride and acrylic esters for which particular advantages were claimed. In the areas of application there were papers discussing the use of hot-melt materials in carpet production, in interlinings and textile laminates, in the
shoe industry and in the growing field of motor car manufacture. There were also accounts both of techniques which may be used for applying hot-melt materials and of some of the problems and faults which may arise during their processing. An unusual paper was the one which came from China and was read in translation. This gave a review of the current uses and the development trends with polyethylene, with ethylene vinyl acetate, with polyamide and with copolyether/ester materials in China. A rather sparse account, but nevertheless useful because information from there is less than common. It is necessary to recognize the proper place of this conference amongst the variety which are currently available. The intention was to provide a contemporary 'state-of-the-art' account of a very particular sector of the adhesives industry. It was not a forum for
consideration of the more arcane theories nor of the latest brainchild of the synthetic chemist which might possibly have some uses. It gave an account of what is practical and is in production, of real use at the moment, together with sufficient information about chemistry, composition and properties to support their application. One had to expect that the commercial aspects would receive more attention that at some other events and recognize the pressures to which salesman (even if technical salesman) are subject. Most of the speakers achieved a reasonable balance between useful technical information and blatent trade propoganda. Overall the event succeeded in its quite valuable objectives and the organizers are to be congratulated on a successful event.
K.W. Allen
Rubber-Metal Bonding NovoteI-Les Halles, Paris, France, 18 June 1987
Organized by: Association Franqaise des Ing~nieurs du Caoutchouc et des Plastiques (AFICEP) and Association Franqaise des Ing~nieurs et Techniciens de I'Electrolyse et des Traitrnents de Surface (AITE) The aim of this day was to permit the exchange of information between surface treatment and rubber specialists, in order to define the best conditions for adhesion between rubber and metal. After the welcome introduction by G. Flauraud for AFICEP and by J.C. Catonne for AITE expressing the need for such studies, Professor J. Lacombe, who presided at the meeting, emphasized the importance of surface treatments in the field of bonding and adhesion before introducing the programme. In the first session, a review of the seven classical theories of adhesion, usually applicable to the specific problem of polymer-metal adhesion mechanisms, was given. The notion of potential surface free energy, which expresses the ability of the polymer surface to reconstruct in contact with a given medium, has to be taken into account especially in the study of polymermetal adhesion (L. Lavielle, CNRS, Mulhouse). P. Marcus (Ecole Nationale Suprrieure de Chimie, Paris) discussed the chemical analytical methods of surface examination by ESCA and Auger spectroscopy, outlining the advantages and disadvantages. In the case of aluminium, the role of magnesium impurity on the surface composition was examined; in rubber-brass joints, ESCA spectra showed the presence of copper sulphide (Cu2S) at the interface after separation. The different treatments applicable to metallic surfaces in order to increase their hydrophilicity and so their adhesion ability were described by J.C. Catonne. Polishing, degreasing and pickling were recommended
to be used in that order. Various mechanical, chemical and electrolytic treatments were detailed. In a well documented speech, A. Katzanevas (Henkei-France) examined rubber-metal adhesion by interdiffusion of the adhesive in the elastomer. Ebonite, isocyanates and resorcinol-formaldehyde resins can be used as chemical adhesives. The need for other supports (polymer, glass) important in the future were mentioned. The different sorts of reactive and non-reactive glues and adhesives were precisely described by G. Kern (Henkel-France), with the corresponding reactions and the working processes given. Numerous formulation parameters for the adhesive, the elastomer, the brassing of metallic surfaces and their consequences on adhesion were detailed by J.M. Beurrier (Vibrachoc, Evry) for m a n y systems. Adhesion is in fact a complicated chemical process. Finally, the more recent non-destructive control tests for rubber-metal joints were reviewed by D. Jahier (CETIM, Nantes). Control by echography, thermography, acoustic emission, holography and radiography are now available. The final discussion ending the meeting showed the necessity for industrial uses to improve the performance of rubber-metal adhesion against temperature increases and corrosive atmospheres. More comparative and ageing studies are needed in that field.
L Lavielle
INT.J.ADHESION AND ADHESIVES OCTOBER 1987
219
view, large-scale use of aluminium/lithium alloys at least seems to be doubtful. On the other hand, the application of carbon fibre-reinforced plastics (CFRP), especially as CFRP/honeycomb sandwich structures, will also be extended to primary structural parts. As a result, in addition to a substantial weight reduction, increased fire protection against the penetration of the flames or collapse of the structure will be achieved compared with metal structures. Furthermore, a great potential for economy in manufacturing costs, utilized inadequately to date, may be exploited by the use of advanced manufacturing techniques and adequate materials, such as superplastic materials. The meeting concluded with a final discussion of the participants together with the readers of the papers under the chairmanship of Dr Brockmann. Afterwards there was a chance to vist the repair shop of Deutsche Lufthansa in Hamburg; most of the participants of the meeting made use of this opportunity. The participants of the BASTART 87 workshop agreed that the meeting was useful for an improved information exchange and hence should be continued.
14. Schafer I~ Wolitz
Second International Conference on Speciality Hot Melts Penta Hotel, Heathrow, UK, 14-1 5 May 1987
Organized by: Dermil Research Limited Dermil Research Limited achieved an attendance of something over two hundred, drawn from at least eight different countries, during their Second International Conference on Speciality Hot Melts. During the two days of the meeting, twenty-two separate papers were given, of which only two were from the organizers. Before plunging into the details of any particular type of adhesive or the intricacies of specific applications, Dr John C o m y n of Leicester Polytechnic laid the foundation with a lucid but concise account of the fundamentals of the whole concept of hot-melt adhesives. This was augmented by a discussion of contributions to adhesive properties by the introduction of functional and polar groups into an EVA copolymer adhesive from the groups at Mulhouse and delivered by M.P. Borg. Then followed a series of papers which fell into two groups (although these were distributed through the two days.) One group dealt with detailed chemistry and uses of individual types of adhesives and their most recent developments. The other group considered areas of industry where hot-melt adhesives have a significant role, and how these roles were (or were not) being played satisfactorily. If I am not to weary my readers beyond endurance it is impossible to consider each of these papers in any detail, so I must select. The choice
218
INT.J.ADHESIONAND ADHESIVES OCTOBER 1987
must be idiosyncratic but I hope will be without prejudice. A dual act by Mr Godfrey and Dr Cooray presented an account of their development of a range of urethane-acrylic prepolymers which are applied by hot-melt techniques but which then cross-link by a second heating. This seems to present some novel features and attracted attention. An alternative system, described by Mr C.M. Allen, was based on a polyurethane prepolymer which is applied as a melt at 60-100°C and then cured by reaction with atmospheric moisture. This clearly implies that there is some time during which the full strength is increasing; with leather this can be as short as 5-8 hours although with metal substrates it may be several days. Another group of more recently developed hot-melt adhesives is being produced from polyamide derivatives of dimerized, unsaturated long-chain carboxylic acids derived from natural fats and oils as described by Dr J. Wichelhaus. Then there were accounts of copolyester (dimethyl terephthalate) resins and of copolymers of ethylene with maleic anhydride and acrylic esters for which particular advantages were claimed. In the areas of application there were papers discussing the use of hot-melt materials in carpet production, in interlinings and textile laminates, in the
shoe industry and in the growing field of motor car manufacture. There were also accounts both of techniques which may be used for applying hot-melt materials and of some of the problems and faults which may arise during their processing. An unusual paper was the one which came from China and was read in translation. This gave a review of the current uses and the development trends with polyethylene, with ethylene vinyl acetate, with polyamide and with copolyether/ester materials in China. A rather sparse account, but nevertheless useful because information from there is less than common. It is necessary to recognize the proper place of this conference amongst the variety which are currently available. The intention was to provide a contemporary 'state-of-the-art' account of a very particular sector of the adhesives industry. It was not a forum for
consideration of the more arcane theories nor of the latest brainchild of the synthetic chemist which might possibly have some uses. It gave an account of what is practical and is in production, of real use at the moment, together with sufficient information about chemistry, composition and properties to support their application. One had to expect that the commercial aspects would receive more attention that at some other events and recognize the pressures to which salesman (even if technical salesman) are subject. Most of the speakers achieved a reasonable balance between useful technical information and blatent trade propoganda. Overall the event succeeded in its quite valuable objectives and the organizers are to be congratulated on a successful event.
K.W. Allen
Rubber-Metal Bonding NovoteI-Les Halles, Paris, France, 18 June 1987
Organized by: Association Franqaise des Ing~nieurs du Caoutchouc et des Plastiques (AFICEP) and Association Franqaise des Ing~nieurs et Techniciens de I'Electrolyse et des Traitrnents de Surface (AITE) The aim of this day was to permit the exchange of information between surface treatment and rubber specialists, in order to define the best conditions for adhesion between rubber and metal. After the welcome introduction by G. Flauraud for AFICEP and by J.C. Catonne for AITE expressing the need for such studies, Professor J. Lacombe, who presided at the meeting, emphasized the importance of surface treatments in the field of bonding and adhesion before introducing the programme. In the first session, a review of the seven classical theories of adhesion, usually applicable to the specific problem of polymer-metal adhesion mechanisms, was given. The notion of potential surface free energy, which expresses the ability of the polymer surface to reconstruct in contact with a given medium, has to be taken into account especially in the study of polymermetal adhesion (L. Lavielle, CNRS, Mulhouse). P. Marcus (Ecole Nationale Suprrieure de Chimie, Paris) discussed the chemical analytical methods of surface examination by ESCA and Auger spectroscopy, outlining the advantages and disadvantages. In the case of aluminium, the role of magnesium impurity on the surface composition was examined; in rubber-brass joints, ESCA spectra showed the presence of copper sulphide (Cu2S) at the interface after separation. The different treatments applicable to metallic surfaces in order to increase their hydrophilicity and so their adhesion ability were described by J.C. Catonne. Polishing, degreasing and pickling were recommended
to be used in that order. Various mechanical, chemical and electrolytic treatments were detailed. In a well documented speech, A. Katzanevas (Henkei-France) examined rubber-metal adhesion by interdiffusion of the adhesive in the elastomer. Ebonite, isocyanates and resorcinol-formaldehyde resins can be used as chemical adhesives. The need for other supports (polymer, glass) important in the future were mentioned. The different sorts of reactive and non-reactive glues and adhesives were precisely described by G. Kern (Henkel-France), with the corresponding reactions and the working processes given. Numerous formulation parameters for the adhesive, the elastomer, the brassing of metallic surfaces and their consequences on adhesion were detailed by J.M. Beurrier (Vibrachoc, Evry) for m a n y systems. Adhesion is in fact a complicated chemical process. Finally, the more recent non-destructive control tests for rubber-metal joints were reviewed by D. Jahier (CETIM, Nantes). Control by echography, thermography, acoustic emission, holography and radiography are now available. The final discussion ending the meeting showed the necessity for industrial uses to improve the performance of rubber-metal adhesion against temperature increases and corrosive atmospheres. More comparative and ageing studies are needed in that field.
L Lavielle
INT.J.ADHESION AND ADHESIVES OCTOBER 1987
219