Technique collage : Vocabulary and technique of collage

It appears here only of the basic words which are useful in industry of the joining which can interest on a purely documentary basis the artists collagists.

- Adhesive of reaction : it is an adhesive with several components which must be mixed before the application. The preparation must be implemented during a certain lapse of time (lifespan out of pot). It also can that it is about an adhesive with only one component which reacts under the action of moisture, of heat

. - Thermofusible Adhesives : in fact adhesives are fluxed by heat before the application. Final hardness is reached by cooling and/or chemical reaction. - Adhesion: They are the intermolecular forces to the interface between material to be stuck and the adhesive preparation. - Self-adhesive Joining: this type of joining requires self-adhesive adhesives which remain sticking for a long time. In general, the adhesive preparation is coated only on one element, and the parts are stuck after drying, often under a light pressure.

- Joining a face or joining in wet phase : the adhesive preparation is applied only to one or the other of the two elements to be stuck and the elements are assembled during the period indicated

. - Cold Joining: during cold joining, the elements to be bound are assembled during opened time, at ambient temperature

. - Joining with heat : in this case there, the elements to be bound are assembled at a temperature of activation and under a pressure given. - self-adhesive: it is a process of joining for which the adhesive preparation is applied to two surfaces to stick. After complete evaporation of solvents, the two elements are assembled in pressure. The initial catch is very high

. - Adhesive containing solvents : it is an adhesive which contains the solids in dissolved preparation

. - Adhesive of dispersion : they are adhesives which contain solids, finely dispersed

. - Maximum Concentration with the site of work : by maximum concentration with the site of work, one includes/understands the highest concentrations at the place where one works of solvent vapors in the air

. - Lifespan out of pot : the lifespan out of pot is an indication concerning the adhesives with two or several components. It describes the period during which a preparation can be implemented.

- Dry Extract : the dry extract is indicated in % and represents the share of solids (they are the nonvolatile matters) of an adhesive. - Inflammability: inflammability is an indication concerning the regulations of safety and indicates the flash point or the point flash.

- Limit of explosiveness : the range in which the ignition of a vapor mixture of solvent-air can explode calls limit of explosiveness or beach of inflammability.

- Not flash : indication of the temperature to which are disengaged from the vapors in sufficient quantity to cause the formation of a detonating air-steamer mixture

. - Report/ratio of mixture : this indication defines the parts in weights which must be mixed for adhesives with several components.

- Source of ignition : in a company, there is a great potential of sources of ignition. One can quote the naked flames, the blowpipe flames, the tobacco in ignition,… There are also hot surfaces, electricals appliance

. - Open Time : this time indicates the maximum lapse of time which can pass between the gluing and the assembly of elements during joining contact.

- Viscosity : viscosity represents the rheological behavior of a matter.

Technical collage 4 : conclusion

The important progress made in the field of the adhesives (generic term of the adhesives, cements and coating) allows the assembly of the near total of materials. The technical and economic consequences make that they are used more and more in sectors as various as mechanics, the textile, wood, transport, the building.

It is in the assembly that the evolution is most spectacular because sometimes, if joining replaces the means traditionally employed, it has the advantage of widening in an important way the framework of the applications. So it is often preferred for one or more of the following reasons:

Uniform distribution of the efforts on the whole of film of adhesive

Price with the m ² often less low Invisible means of assembly (decoration)

Sealing and protection counter corrosion carried out at the same time as the Suppression assembly of the resumption of parts (fettling, sandpapering, cementing.)

Very different material assembly

But all these qualities should not make forget that joining is technique of a modern and rather complex assembly to implement. It is necessary to have good knowledge in the theory of the adhesive to be able to apply this method under satisfactory conditions.

Collage should not be a palliative or a spare wheel. It is necessary to think of joining as of the design of the product. The conditions of success are all the more large as one controls the theory of the adhesives and that one has good notions of the adhesives available on the market.

Si votre soif de connaissances sur le collage n'est pas étanchée après tout ça, le Laboratoire de Matériaux vous propose les deux ouvrages suivants écrits au laboratoire:

Le collage structural moderne (Théorie et pratique) de Patrice Couvrat Éditions: TEC & DOC LAVOISIER (1992)
Le collage moderne de Patrice Couvrat Collection: Technologie de pointe Éditions: HERMES (1990)

Origin of the techniques of collage and the adhesives

The use of adhesives was known as of 4500 front JC.

These adhesives were composed of raw materials animal and vegetable, as the adhesive of bone (animal grease) and casein, as well as tar, pitch, waxes, etc It is only at the end of the 19iéme century (in approximately 1876) that one produces the first resin and rubber solutions with benzene which are used for a relatively reliable joining of wood, paper, paperboard, fabrics and leather.

At the beginning of the 20th century, appear the first adhesives containing nitrocellulose which allow an assembly of construction, partly without use of average mechanics. Because of decisive progress in the field of macromolecular chemistry, the bases of the modern techniques of joining were installation. It is into 1949 that the adhesives on the basis of Neoprene are introduced.

The means of joining evolve/move and gain more and more importance in the current methods of industrial production. The advantages of joining are numerous. One can think for example of

Homogeneous distribution of the forces on all stuck surface. - Not - Deterioration of materials contrary to riveting, nailing. - Saving in weight (application on materials low thickness - effect of against plating: low-weight material but of high solidity) . - Widening of the possibilities of combinations of materials.

Technical collage 2 : Adhesion know minimum

The adhesion of a liquid on a solid utilizes two independent concepts :

- The solid liquid interaction which characterizes adhesion.

- The damping which characterizes the spreading out of the liquid on the solid.

Some considerations on absorptivity

It represents the aptitude which greatest possible surface has a liquid to occupy when one lays out it on a solid surface. We will quantify it by the introduction of the concept of energy of surface of a liquid or a solid.

Énergie superficielle d'un liquide

Surface energy of a liquid

As called surface tension, it characterizes the aptitude as for the surface of a liquid to take the smallest possible value in a given medium. It also characterizes the cohesion of a liquid since it is necessary to overcome the forces of internal cohesion of this one to increase this surface.

Mechanically, it is expressed like a force being opposed to an increase in surface and brought back to the unit of length. The unit used is N/m

Tension superficielle forte ( mauvais pour le collage).

Tension superficielle faible ( bon pour le collage).

It represents the quantity of work which it was necessary to spend to create the aforementioned surface, the temperature and the pressure being constant. It is expressed in J/m ².

Concepts of absorptivity

Let us pose a drop of liquid on a solid surface.

The balance of the forces gives the equation of Young :

g lv cos q + g sl = g sv

Where G S, G sl, G L represent the energy of surface of the solid, interfacial energy liquidates solid and the surface tension of the liquid.

Critical surface energy

The spreading out of the liquid is perfect only if the contact angle A is null. This value corresponds to a breaking value of the surface energy of the solid which makes it possible to predict that if :

g l < a="0,">

g l > g c alors A is positive, damping is bad.

Which are the connections which intervene ?

One thus qualifies the whole of the forces which are established between the adhesive and the surface of the solid. Several explanations exist, without one being able to generalize one or the other of those.

- Mechanical Theory. Adhesion was regarded a long time as being a simple mechanical problem, the solidity of the joint resulting from the penetration of the adhesive in the asperities of solid surface. Explain part of adhesion.

- Electric Theory. Adhesion would be due to the establishment of an electric layer to the interfaces, the forces being of electrostatic nature. Very discussed.

- Chemical Theory. It interprets the connection by the formation of covalent bonds between two involved bodies. Has place only in certain cases.

- Theory of the diffusion. There is inter-diffusion between two involved surfaces. It supposes the mutual solubility of materials. Joining of PVC for example.

- Thermodynamic Theory. It indicates the establishment of weak connections (forces of Van Der Waals) between surfaces. These forces are exerted on short distances and exist in all the cases of figure. Explain a good part of adhesion.

The forces of Van Der Waals result from the dissymmetry of burden-sharing positive and negative involving the formation of dipoles as well in polymer as in the substrate and linking themselves head-digs. These various assumptions show that the phenomena of adhesion are not yet well elucidated. It seems however that the establishment of weak but very many connections is one of the principal reasons of adhesion in much of case.

Importance of roughness

An increase in roughness has two direct incidences:

- A better mechanical anchoring.

- A rise in the real surface of contact (10 to 100 times apparent surface). One could then expect that the resistance of the joint increases in similar proportions.

However it is not the case. Two essential reasons explain these observations.

Le mouillage n'est pas réalisé dans les creux. Il y a concentration de contraintes au sommet des aspérités.	Sans creux, le mouillage est mieux réalisé. Le sablage à créé des angles très ouverts, l'adhésion sera donc meilleure.

TO RETAIN ABSOLUTELY

- Absorptivity must be the best possible one so that the maximum of connections are established between the adhesive and the substrate. The equation of Young indicates to us that a surface treatment is practically essential so that the energy of surface of the substrate is maximum. These treatments must have like principal goal to clean the solid surface of all the elements likely to establish a barrier with the establishment of the connections.

- The surface tension of the adhesives used must be lower than the energy of surface of the solids considered. This is why it is extremely difficult to stick plastics at the rough state.

- A good absorptivity is not a sufficient condition, still is necessary it that it is formed connections many and solid, which supposes that the geometry of surface is well known and that the chemistry of the adhesive and solid surface are adapted perfectly.

JOINTS

There, if I am a a little mechanic, I see well that it is necessary to avoid cleavage and peeling….But shearing ?

If I believe Volkersen of it, attention should be paid, because the constraints are not very homogeneous.

The reader will be able to refer to the two books indicated to have more information in this field, because it is true that that starts to become complicated ...... .

I retain nevertheless that the constraints must be distributed on the whole of the joint for better resisting the efforts applied

Technical collage 3 : Various Adhesive

An adhesive, it is first of all a basic polymer which gives the cohesion of the unit. It is then the addition of elements intended to increase the sticking capacity, to increase the flexibility in certain cases.

Let us start with the structural adhesives

The concept of structural adhesive appeared when one started to carry out adhesive bonded joints being able to support constraints as important as the assemblies mechanic - welded. The adhesive bonded joint then has a resistance equivalent to that of materials constituting the structure.

The adhesive is integral part of the whole of the structure to the difference of the products of coatings or cements of sealing, from where the name of structural adhesives.

They are conceived to resist constraints higher than 7 MPA (it is not an insuperable border! …) at ambient temperature. They can be requested without failure with a high percentage of their maximum resistance for a long period, this under hostile conditions (low temperatures, heat, chemical agents,…).

POLYURETHANS

It is a very vast class of products of which some can be classified among the structural adhesives. They are then reactive polymers without solvents or with very high dry extract. They result from condensation between a monomer isocyanate and a monomer hydroxide or polyol. They are appeared as Bi-components but the evolution tends to support the development of the adhesives polyurethanes mono-components because of their simplicity of implementation. They have an excellent behaviour with peeling, with the tear. The polyurethanes Bi-components are regarded as a semi-structural adhesive. They are appropriate perfectly for the mixed assemblies plastic metal/. Certain manufacturers develop polyurethane mono-component ranges. These adhesives are presented under a pasty state then become after reticulation with the ambient moisture of the elastic masses.

The excellent properties of adherence of the polyurethanes found applications in the adhesives to means and high module in all the industrial branches of industry, in particular each time the assemblies are subjected to dilation, of the shocks or the consequent vibrations. They find many uses in fields as different as the means of transport, the shipbuilding, the electric components,… The polyurethanes are slower than epoxies but on the other hand they are much more flexible. Moreover one can stick them on practically all surfaces without using primary educations of adhesion. The latter are necessary only on Teflon,…, i.e. of the materials which are supposed incollables.

One of the large advantages of the polyurethanes currently on the market are that they stick glass without primary education. There is thus a use much simpler than with epoxy. On the other hand if one wants a rapid hardening one frequently uses mixed joinings: polyurethane and adhesive tape. One limits the use of the adhesive tapes because they are of a rather high cost. There are polyurethanes Bi-components. The latter have the advantage of showing higher mechanical characteristics but their implementation is much more complex. They are hard to spread out and the investments are heavy.

The manufacturers now develop mono-components with characteristics which tend to approach those of the Bi-components. One of the principal applications of the polyurethanes is the joining of glass. On the other hand they have a bad behaviour with UV. Many research is undertaken in order to reduce this problem (problem of the joining of avoid-break cars). Another application of these adhesives is the realization of groundsheet, of, assembly seals of elements of boats,… One exploits much the fact of the great flexibility of these adhesives. One speaks besides rather often about flexible joining for the polyurethanes mono-components.

The principal characteristics of the polyurethanes are :

- Important Elasticity and flexibility even at low temperature - Good adherence to the majority of materials - Good resistance to the ageing

- Resistance to the not diluted acids - Good behaviour with moisture - Behaviour at the average temperatures (80-90 °C)

- Hardening hot fast (mono-component) - Speed of reticulation from 3 to 5 MM per day for the mono-components - Implementation technical for the Bi-components

- Electrical insulator Property, property of sealing

- Absence of toxicity in the majority of the cases - Need for drying ovens for the mono-components - Shear strength less low than the other structural adhesives

- Very good Hardness At present, of the manufacturers polyurethanes mono-components market which do not have any more their principal defect i.e. slowness of polymerization. This new adhesive is obtained by the presence of an activator. One thus has the advantages of a polyurethane mono-component (ease of use) and those of Bi-components (speed of catch).

EPOXIES

They are the thermohardening adhesives among most current and most powerful. Their denomination comes from the presence of a characteristic grouping called epoxy grouping. The formulations are presented in the form of liquid or pasty products according to case's.

They are adhesives without solvents, mono or Bi-components. For the adhesives Bi-components, the mixture hardener basic resin is made at the time of joining, by respecting the quantities strictly. An exothermic reaction takes place then, allowing the reticulation. Generally, joining is made at ambient temperature but it can be accelerated by a contribution of heat. For the adhesives mono-components, the adhesive is ready with employment i.e. that the basic resin and the hardener cohabit without the reaction taking place. It is necessary to have a contribution of heat so that the reaction occurs.

The conditions of storage are important: the temperature should not exceed 20 to 30 °C, with the risk to cause a beginning of reaction. The epoxies are frequently used for joinings metal/metal or plastic metal/having to resist very high mechanical constraints. They offer a very good adhesion on the majority of materials and an excellent resistance to the ageing. For epoxies being able to tolerate high temperatures, one inserts ceramics particles.

The problem is then the handling time which reaches 24 H. research is centered on the behaviour in temperature of these adhesives like on the increasingly current realization of epoxy mono-component to high mechanical characteristic. One markets epoxies with rapid hardening, semi-rapid, normal. But resistance drops as the time of catch shortens. It is thus necessary to find a compromise between the requirements of speed of industrial realization and the behaviour of joining.

Let us quote like characteristics for the mono-components:

- Excellent resistance in temperature being able to go from -55 to +200 °C - Excellent shear strength: up to 40 MPa with 20°C - Excellent behaviour with the environments

- Excellent resistance to oils, solvents

- Storage with +4 or -18 °C - High Price - Harmfulness - Unflexibility

For the epoxies Bi-components, one can quote:

- Excellent resistance in temperature

- Excellent shear strength

- Good behaviour with the environments

- Good resistance to oils and solvents

- Possibility of reducing the duration of polymerization by increasing the temperature

- Storage at ambient temperature

ACRYLIC RESINS

There are several types of adhesives at acrylic base.

CYANOACRYLATES

In fact rather recent adhesives make rather important great strides because of some of their characteristics. The reaction is a simple reaction of polymerization of anion type, caused by the presence of a weak base on surface considered. At the beginning these adhesives were intended only for the joining of metals/rubber. Now, one also uses them for porous materials. The principal characteristics of these adhesives are:

- A speed of polymerization low in general but it strongly depends on the nature of the supports - Moisture is a good catalyst

- Polymerization takes place by compression of fine film of monomers - This polymerization takes place on a nonacid polar surface

- The mechanical resistances are high - Their resistance to solvents is good - They have a strong covering capacity

- Their behaviour at the temperature is low - The film is colourless In fact rather specific adhesives are in general intended for the precision tool industries. One uses them on small parts, for the joining of rubber seals,… They resist the shocks generally rather badly, at the temperature (100 °C).

But now certain manufacturers market cyanoacrylates which resist 150 °C, with sets of 0.25 mm, shocks, moisture. One thus eliminates the principal defects from this type of adhesive. One of the great advantages of these adhesives is to be able to adhere on famous surfaces incollables thanks to the use of primary educations of adhesion. One avoids thus on polypropylene, Teflon,…, of the surface treatments such as a plasma treatment followed by CORONA effects.

ANAEROBES

It is thermohardening adhesives for which polymerization can take place only in the absence of oxygen or of air. Metal surfaces have the property to catalyse the reaction but this one also requires the action of an activator or electromagnetic radiations such as the ultraviolet rays.

pplication of brake net to block the threaded assembly.

The principal characteristics are:

- Their time of weak catch

- An excellent shear strength but a very low tensile strength

- Their thermohardening character confers excellent characteristics according to the temperature to them. Some can hold up to 180 °C.

- Their chemical inertia is very good.

- They are unsuited to porous materials. Their fluidity is more or less important to supplement the plays. One uses them for the braking of nets, mechanical joining for the bearings.

The play must remain weak and lower than 0.25 Misters.

The principal parameters on the condition of uses of these adhesives are :

The nature of the substrates: metals are reactive to differing degree, the other materials require the use of the activators.

The play interfaces: the time of polymerization increases quickly with the play.

The choice of the product: with origin, various products can be equipped with different sensitivities to the anaerobic effect, with metals, even with radiation UV.

The cleanliness of surface: dirty surfaces delay polymerization and reduce the performances of the product. The surface treatments of ask for the use of more reactive products or a preparation of the activator. Activators: they are solvents containing of the active ingredients which remain on surfaces after evaporation. Their action is essential with certain adhesives or on nonreactive substrates.

ANAEROBES REACTIVABLES WITH UV

There is a reactivity for lack of oxygen and the presence of U.V.

This adhesive is used for the joining of glass on any support. Polymerization takes place into 20 S if there is a lamp UV, and of 24 H with the action of the sun.

This adhesive is important in optics, the construction of mirrors, decoration,…

They are very interesting since they have the same refractory index as glass. There is not thus a problem for industries of optics. It is possible to clean the surface which was exposed to the action of the air. This type of adhesive is used much in the sector of decoration.

ACRYLIC RESINS MODIFIED

There is, compared to the traditional acrylic resins, the appearance of a radical urethan.

This modification involves completely particular characteristics. Hardening is made possible by the addition of two different parts: an activator and adhesive.

The adhesive is consisted of the basic resin whereas the activator consists of peroxide. The principal characteristics of the acrylic resins modified are:

- A very fast catch, a few minutes for the catch in hand, a few hours for final resistance. - Adherence to badly prepared surfaces.

- A good behaviour at the temperature. - A very good shear strength. - The strength to the chemical agents and moisture is very honest.

- The thickness of the joint must be low. They are used for manufacture in chain because the time of catch is rather weak contrary to epoxies. On the other hand this type of adhesive cannot be used in all the cases of figure. For example the following assembly cannot be carried out with adhesive of an acrylic type modified. This type of joining is impossible to carry out with an acrylic resin modified. Indeed the adhesive is liquid whereas the activator is viscous. The adhesive is thus driven out at the time of the hafting. If the detail of joining observes, we have :

THERMOFUSIBLE THE ONES GOLD HOT-MELTS

At the beginning they were used for joining paperboard/paperboard and of Wood. One quickly realized that they were whitebait to stick much of other things drank. Their principal immediate advantage is the wrestling. In fact adhesive cuts the effect of having to Be heated in order to Be fluxed, the wrestling taking place with cooling. They cuts has problem: during the application one cold materials, there edge Be the formation of has thin to bush-hammer (glacis has) which prevents joining. They consist of has BASIC polymer, has resin and has wax to which one adds additive stabilizing gold plasticizing. The BASIC polymer is intended to give cohesion, the behaviour thermal At the temperature and stability while the waxes cuts the aim of controlling viscosity. The resin tacktifiante is intended to increase the hot sticking capacity. The BASIC polymers are primarily copolymers of ethylene such have the EVA. One also finds polyesters and polyamides. From to their rather easy handling and to their time of weak wrestling, thesis adhesive make rather fast great strides. One principal edge give the advantages of this adhesive: - Setting misses fast -100% of dry extracts from where has facility of handling - Adherence to many supports - Absence of solvents - Réactivable hot permanently - Facility of uses - Machines adapted to evolutionary spleens (folding camera machine-splicing units) Goal one the other hand there are some defects: - Insufficient Creep strength - Speed of sensitive solidification to the temperature of the support - Delicate Compromised between speed of time of wrestling and the time of opening - Sensitivity to heat At the beginning the BASIC component was the acrylic resin. At present drank, the manufacturers uses the thermofusible ones containing mono-component polyurethane. They are packed in hermetic cartridges and in solid form. There are the advantages of has traditional HOT-MELT. Joining is done by heating. Adhesive Then the plays the share of has traditional polyurethane. There is thus has polymerization. The advantage is that the behaviour is fixed. It will not move any more. Moreover the wrestling is fast. Adhesive It is year miracle drank its implementation is complex. Indeed, ounce the cartridge is open to use must uses it until the end. It is necessary to uses has special and expensive gun. One must moreover had has heater of cartridge. Finally the gun must Be imperatively cleaned with has special solvent after each uses. Yew not, the adhesive polymerizes and stops the gun. One thus has in maintenance and has material rather heavy and expensive.

ADHESIVES IN AQUEOUS DISPERSION

All the products of this family are adapted perfectly to answer a great number of industrial requests. Their use is advised where the products in phase solvent are prohibited. Indeed the adhesives in aqueous dispersion have the advantage of being much less toxic than an adhesive solvent and to be flammable in the liquid state (interest on the level of storage and implementation).

These products give excellent results on a great number of supports such wood, the plastics, the fabrics, etc As example, these adhesives are used today for the fabric fixing on wood in the manufacture of speakers like for the joining of wall linings in particular in public transport.

These products also are very much used in the manufacture of industrial filters, of light materials, like for the assembly of products of insulation. The adhesives in aqueous dispersion result in general from two technologies:

- The adhesives contacts: a double gluing is carried out, one waits the time of evaporation necessary and one posts the two surfaces pasted by maintaining the pressure

- Self-adhesive adhesives: After complete evaporation of solvent (in fact of water), these products remain self-adhesive very a long time. That gets a great flexibility on the level of the process of implementation of the product. A contribution of heat can decrease in a considerable way time of drying of the adhesive. The adhesives in aqueous dispersion have a rate of rather important dry extracts in general. One can often stick with one liter of adhesive in dispersion a surface much more important than with one liter of solvent adhesive. For the implementation of these products, one can apply them without problem to the brush, the roller or the gun. ADHESIVE TAPES One distinguishes several kinds of structural adhesive tapes: supported films, the not supported films époxys, and finally acrylic films. The supported films have been developed for several years but are used little. The structural films mono-components have characteristics higher than the traditional epoxy adhesives. The joints can reach more than 30 to 35 MPA in shearing and from approximately 12 to 13 N/MM in peeling. They make it possible to fill rather important plays. A contribution of heat is necessary to ensure a good polymerization. There are many applications of the adhesive tapes:

- Traditional Joining - Ribbons for the electrical engineering

- Ribbons of protection for plastic condensers - Ribbon of masking (gilding of the contacts of printed circuits) - Adhesive tapes of saving for the surface treatments

- Working Ribbons of assemblies and refermables

- Antiblocking industrial Adhesive tapes Foams and the transfers very high adhesion are acrylic adhesives comparable with adhesives doubles faces. There are various types of adhesive masses on the market: - Rubber

- Natural rubber - Synthetic rubber - Nonthermohardening Rubber - Thermohardening Rubber - Réticulé thermohardening Rubber

- Acrylic resin

- Thermohardening Acrylic resin

- Réticulée Acrylic resin

- Silicone

- Thermohardening Silicone The most effective adhesive is that containing acrylic resin. It is the only one which can be regarded as structural. This type of joining has been known for more than 20 years. At the beginning they were primarily epoxy resins, D-activables hot more pressing. For 15 years the most powerful ribbons have been containing acrylic resin. There is a support, foam, and the adhesive.

One can fill rather important defects with the thickness. On the other hand one realized that when one made work this type of assembly, there was risk of rupture on the level of foam. The manufacturers currently market adhesives containing acrylic resin pure. The problem of foam thus is avoided.

There is according to needs' a more or less great thickness for the ribbon. For the low thicknesses there is acrylic resin pure. On the other hand for the ribbons stronger thicknesses there is acrylic resin emulsified. These products are rather interesting bus in addition to exceptional performances with wrenching and with shearing, they have a viscoelastic memory.

One can thus stick two materials with different dilation coefficients. The ribbon lengthens but does not break. One can also quote aptitudes of impact resistance, vibrations, corrosion, of electric insulation,…

They are moreover ungluable. Like example of use, one can quote the manufacture of the electrical equipment boxes. In the past, one placed a reinforcement in the shape of omega. It was then necessary to weld it then to sandpaper it for the application of painting. Maintaining with the presence of ribbons with very high properties of adhesion, the operation of sandpapering is not effective any more. This saving of time was not possible that because the new ribbons resist strong temperatures. One can quote, for example, with range VHB from 3M: 250 °C during 4 H, 150 °C uninterrupted.

Research is currently centered on the development of ribbons supporting still better heat and with the mechanical characteristics definitely more powerful.

PRIMARY EDUCATIONS Of ADHESION: THEIR FUNCTIONS

ls consists of a resin and often of polyurethane. This is why they are manufactured by the industrialists of the adhesive. The function of the primary educations is very vast. They have been developed for a few years for quite particular employment. Let us quote for example: - Concrete Accelerator of the instantaneous adhesives - Preparation of surface - Degreasing of surfaces - Increase in adhesion on the plastics, glass - Agent of polymerization - Gelation of the visible adhesive - They are used also as barriers with plasticizers, the gasolines, etc

PRESENTATION OF SOME OTHER EXISTING ADHESIVES

The adhesives from the basic nature of polymer and that of the additives, represent a very vast family which it would be tiresome to detail. We will thus limit ourselves to a fast and brief presentation of the other adhesives.

EMULSIONS AND SOLUTIONS

They are adhesives in aqueous or organic medium whose hardening results from the evaporation of solvent or its absorption by one or the other of the substrates. The natural adhesives of vegetable origin do not use an organic solvent.

The adhesives obtained starting from resins

thermoplastics, of thermohardening elastomer adhesives even, can according to case's being obtained either in aqueous medium, or in solvent medium. $ The natural adhesives cannot be qualified the structural ones but they however are very much used in the industry of wood, paper, delivers,…

THE ADHESIVES CONTACTS

The setting in contact of surfaces to be assembled takes place only after the evaporation of solvents, the assembly requiring a pressure to weld two films of adhesive. The typical example is the Néoprène adhesive.