Good adhesion what. What is cement adhesion? An excerpt characterizing Adhesion

Thanks to the development of new technologies in dentistry, today we have the opportunity to restore the integrity and functionality of damaged and decayed teeth quickly, efficiently and for a long time. Adhesive systems provide reliable fixation of fillings and artificial prosthetic structures.

In this article, we will look at what adhesion is in dentistry and how it works in the service of a beautiful and healthy smile.

Adhesion - what is it

In general, the word "adhesive" in translation from of English language means "adhesive substance, sticking". This "glue" is used in dentistry in order to connect materials of different composition with the tooth tissue (do not confuse adhesion and cohesion - this is a physical term).

By itself, the filling material does not have chemical adhesion, that is, the ability to adhere to naturally moist dentin, so a “mediator” is needed here, which will take care of the reliable adhesion of two dissimilar tissues. During polymerization, the composite material shrinks, so if adhesive systems are not used, the desired adhesion quality cannot be achieved. And this is a direct road to the development of repeated caries or even under a filling.

“I have been worried about my diastema since childhood, . About 5 years ago, I heard that there is such a technique as adhesive reconstruction of teeth, in which no painful grinding is needed and the material literally “sticks” to the teeth. The doctor simply polished the enamel of the front teeth and covered the unattractive gap in layers with a composite. The enamel remained intact, and the smile became open.

Elena Salnikova, review on the website of one of the Moscow dentistry

Innovative light-curing adhesive systems are used for filling teeth with composites, for fixing bridges, as well as for installing braces, veneers, skyces.

Classification of adhesive systems

In essence, the composition of the adhesive system is represented by a group of liquids from the etching component, the bond, and the primer. Together they provide micromechanical links between artificial materials and dental tissues.

Since the structure of enamel and dentin is heterogeneous, the adhesive systems used for them are also different. In the classification of adhesive systems, options are distinguished separately for enamel and separately for dentin.

Modern adhesive systems differ in the following characteristics:

the number of components that are included in their composition (1, 2 and more),
filler content: if acid is present, it is a self-etching adhesive system,
curing method: self-curing, light-curing, and dual-curing.

So, in the composition of enamel adhesives - low-viscosity monomers of composite materials. Important point is that enamel adhesives do not work on dentin. Therefore, it is important either to put insulating pads for the hard part of the tooth, or to use a special dentin adhesive - a primer.

What are the types of adhesion

There are several types of adhesion: mechanical, chemical, and combinations thereof. The simplest is mechanical. The essence of the system is to create micromechanical bonds between the components of the material and the rough surface of the tooth. To ensure high quality adhesion, the natural micropits on the surface of the dental tissues are thoroughly dried before applying the adhesive.

Interesting! Dr. Buoncore found out 63 years ago that phosphoric acid roughens tooth enamel. This helps to enhance the adhesion of the composite to the tooth tissues. Appeared more than half a century ago, the technique of etching tooth enamel with acid became the foundation for modern adhesive restorative methods.

The chemical bonding option is based on the chemical bonding of the composite material with enamel and dentin. Only glass ionomer cements have this type of adhesion. Other materials used by dentists have only mechanical adhesion.

How does the composite “stick” to the enamel surface?

As noted above, in dentistry, the mechanisms of adhesion to enamel and dentin differ. The protective outer shell of the teeth is transformed under the influence of acids. If we examine the enamel after acid etching under a microscope, it will resemble a honeycomb. The acid in this case works to strengthen the bond with the composite. As a result, viscous hydrophobic adhesives penetrate deeper layers of enamel more easily and ensure its strong adhesion to the composite.

Interesting! Enamel is considered the hardest tissue in our body. It contains the most a large number of inorganic substances - approximately 97%. The remaining 2% is water, 1% is organic matter.

How enamel is etched

This treatment method involves removing a portion of the 10 micronewton (µN) layer from the enamel. As a result, pores with a depth of 5–50 μN appear on its surface. Often, enamel is lubricated with phosphoric acid for etching, but organic acids can be used for dentin, but in a low concentration.

The etching process lasts from 30 to 60 seconds. Crucial have individual characteristics structure of the enamel surface, in particular its initial porosity. If the acid is overexposed, it will inevitably affect the structure of the enamel and weaken the adhesion. So if the patient's dental tissues are rather weak, then the etching should last no longer than 15 seconds. The acid is removed with a jet of water, and for the same amount of time as it is kept on the enamel.

How does the composite adhere to the dentine surface?

The properties of dentin are such that its outer layer is moist. The fluid in this part of the tooth is updated quickly, so it is very difficult to dry it. And so that moisture does not affect the quality of adhesion of dentin to the composite, special water-compatible (scientifically - hydrophilic) systems are used. Also, the bond strength is directly affected by the so-called “smear layer”, which occurs as a result of instrumental processing of dentin. There are 2 approaches to using linking mechanisms:

the smear layer is impregnated with water-compatible substances,
the smeared layer is artificially dissolved and scraped off.

It is worth noting that the latter method, which involves the removal of excess microparticles from the surface of the enamel, is now used much more often than the first.

How dentine is poisoned

Japanese dentist Fuzayama 39 years ago was the first in history to apply the dentine etching technique. Today, before the procedure, special conditioners are applied to the tissues of the teeth - they help hydrophilic substances to penetrate deeper into the dentinal tissues and adhere to the water-repellent composite. At the same time, the smeared layer partly leaves, the dentinal tubules open, and mineral salts come out of the upper layer. After that, the conditioners are washed off with water. Next comes the drying stage, and the main thing is not to overdo it, otherwise it will affect the grip.

Next, a primer is applied, which helps the hydrophilic substances to pass into the tubules and adhere to the collagen fibers. As a result, a kind of hybrid layer is formed, which contributes to the effective bonding of the composite to the dentin. It also serves as a barrier against seepage of chemicals and microbes into the internal structures of the tooth.

Adhesive systems for enamel

If we are talking about enamel, then adhesion here is provided on the basis of micromechanical coupling. For this, hydrophobic liquids are used, however, they will not give the necessary “sticking” to wet dentin, therefore a primer is also used. The handling of enamel adhesives having a one-component composition is based on the following steps:

etching the enamel with phosphoric acid - about half a minute,
removing the etching gel with a water jet,
enamel drying,
connection in the same proportion of the substances of the adhesive system,
introduction of an adhesive into the tooth cavity with an applicator,
leveling it with an air jet.

Only after performing all of the above manipulations, the doctor introduces the composite material.

Adhesive systems of different generations in clinical dentistry

To date, 7 generations of adhesive systems are known. Today, dentists use systems, starting from the 4th generation, that help us keep our teeth whole and healthy throughout our lives. They contain 3 components: conditioner + primer + adhesive. But the innovative 6th and 7th generations with single-stage drugs, alas, have not yet become widespread.

Interestingly, many experts talk about the primary role of enamel adhesion, but dentine adhesion comes second. Conducted laboratory research also indicate that today maximum efficiency demonstrates alcohol protocol of adhesion. Ethanol helps to eliminate pain and sensitivity after the procedure. In addition, when using this type of adhesion protocol, there is less leakage of dentinal fluid. However, in each individual situation, the doctor himself decides which protocol and which adhesive system to give preference to in the existing clinical conditions.

1 Protocols for the use of adhesives Popova A.O., Ignatova V.A. - 4th year students of the Faculty of Dentistry.

During large-scale or repair concrete work, situations often arise when it is not possible to simultaneously pour the entire concrete structure.

As a result, cold joints appear at the point of contact of the concrete layers, which lead to loss of strength, loss of water tightness, delamination and other “troubles”.

In this regard, when repairing concrete and reinforced concrete structures, as well as during the construction of screeds, it is necessary that adhesion of concrete to concrete was as deep and reliable as possible.

The main cause of poor adhesion of concrete to concrete and, accordingly, the formation of cold joints and delamination is the natural process of concrete carbonization.

Free lime, as the main source of functional interaction of concrete layers, is practically absent on the surface of "old" concrete. Under the influence of ambient air CO2, active lime turns into calcium carbonate, which is an inert substance that reacts only with acidic compounds.

Therefore, fresh concrete, which has an alkaline reaction, very poorly “adheres” to the old carbonized surface, and if adequate measures are not taken, it will form cold joints or “fall away” over time.

General case of a set of measures to ensure high-quality adhesion of concrete to concrete

Mechanical preparation of the old surface: grinding, dedusting, removal of greasy stains, etc.;
Coating with special primer;
Surface treatment with special compositions "related" to each other;
Surface treatment with compositions with a high degree of "sticking";
The use of compounds that are not “related” to each other in terms of chemical composition.

An example of a set of measures to ensure high adhesion of concrete to concrete

Application of ASOCRET-KS/HB intermediate adhesive on the pretreated surface. Provides required level adhesion to old concrete;
Application of a repair non-shrinking compound with a high rate of curing: ASOCRET-RN - up to 20 mm of adhesion, ASOCRET-GM100 - up to 100 mm of adhesion depth;
Application of finishing solution ASOCRET-BS2.

The above materials have a cement-sand base modified with appropriate additives. So-called "dry polymers" are used as additives, which are powdery high-molecular compounds.

When mixing such mixtures with water, a full-fledged liquid polymer is formed, which gives the composition the required functional property - ensuring reliable adhesion (adhesion) of concrete to concrete.

Adhesion is the bond between dissimilar surfaces brought into contact. The reasons for the emergence of an adhesive bond are the action of intermolecular forces or chemical interaction forces. Adhesion leads to bonding solids- substrates - with the help of an adhesive - an adhesive, as well as a bond of a protective or decorative paintwork with base. Adhesion also plays an important role in the dry friction process. In the case of the same nature of the contacting surfaces, one should speak of autohesion (autohesion), which underlies many processing processes. polymer materials. With prolonged contact of identical surfaces and the establishment in the contact zone of a structure characteristic of any point in the volume of the body, the strength of the autohesive connection approaches the cohesive strength of the material (see cohesion).

What is surface adhesion?

However, high adhesion can also be achieved in this case, if the surface layers of the contacting bodies are in a plastic or highly elastic state and are pressed against each other with sufficient force.

Liquid adhesion

Adhesion of a liquid to a liquid or a liquid to a solid. From the point of view of thermodynamics, the cause of adhesion is a decrease in free energy per unit area of the adhesive joint in an isothermally reversible process. The work of reversible adhesive separation Wa is determined from the equation: >Wa = σ1 + σ2 - σ12

where σ1 and σ2 are the surface tension at the phase boundary, respectively 1 and 2 s environment(air), and σ12 is the surface tension at the interface between phases 1 and 2, between which adhesion takes place.

The value of adhesion of two immiscible liquids can be found from the equation above from the easily determined values of σ1, σ2 and σ12. On the contrary, the adhesion of a liquid to the surface of a solid, due to the impossibility of directly determining σ1 of a solid, can only be calculated indirectly using the formula:>Wa = σ2 (1 + cos ϴ)

where σ2 and ϴ are the measured values, respectively, of the surface tension of the liquid and the equilibrium wetting angle formed by the liquid with the surface of the solid. Due to wetting hysteresis, which does not allow accurate determination of the contact angle, only very approximate values are usually obtained from this equation. In addition, this equation cannot be used in the case of complete wetting, when cos ϴ = 1.

Both equations, applicable in the case when at least one phase is liquid, are completely inapplicable for assessing the strength of the adhesive bond between two solids, since in the latter case, the destruction of the adhesive joint is accompanied by various kinds of irreversible phenomena due to various reasons: inelastic deformations of the adhesive and substrate, the formation of a double electric layer in the area of the adhesive joint, the rupture of macromolecules, the “pulling out” of the diffused ends of the macromolecules of one polymer from the layer of another, etc.

Polymer adhesion

Almost all adhesives used in practice are polymer systems or form a polymer as a result of chemical transformations that occur after the adhesive is applied to the surfaces to be bonded. Non-polymer adhesives include only inorganic substances types of cements and solders.

Methods for determining adhesion

The method of simultaneous separation of one part of the adhesive joint from the other over the entire contact area;
The method of gradual delamination of the adhesive joint.

Pull-off Method - Adhesion

In the first method, the breaking load can be applied in a direction perpendicular to the plane of contact of the surfaces (peel test) or parallel to it (shear test). The ratio of the force overcome with simultaneous separation over the entire contact area to the area is called adhesive pressure, sticking pressure or adhesive bond strength (n/m2, dyne/cm2, kgf/cm2). The tear-off method provides the most direct and accurate characterization of the strength of an adhesive joint, however, its use is associated with some experimental difficulties, in particular, the need for a strictly centered application of the load to the test sample and ensuring a uniform distribution of stresses over the adhesive joint.

The ratio of the forces overcome during the gradual delamination of the sample to the width of the sample is called the peel resistance or delamination resistance (n/m, dyn/cm, gf/cm); often the adhesion determined during delamination is characterized by the work that must be expended on the separation of the adhesive from the substrate (j/m2, erg/cm2) (1 j/m2 = 1 n/m, 1 erg/cm2 = 1 dyn/cm).

Peel Method - Adhesion

Determination of adhesion by delamination is more appropriate in the case of measuring the strength of the bond between a thin flexible film and a solid substrate, when, under operating conditions, peeling of the film usually proceeds from the edges by slowly deepening the crack. With adhesion of two rigid solid bodies, the tear-off method is more indicative, since in this case, when sufficient force is applied, almost simultaneous tear-off can occur over the entire contact area.

Adhesion test methods

Adhesion and autohesion during peel, shear and delamination tests can be determined on conventional dynamometers or on special adhesion meters. To ensure complete contact between the adhesive and the substrate, the adhesive is used in the form of a melt, a solution in a volatile solvent, or a monomer, which polymerizes when an adhesive compound is formed.

However, during curing, drying, and polymerization, the adhesive typically shrinks, resulting in tangential stresses at the interfacial surface that weaken the adhesive bond.

These stresses can be largely eliminated by introducing fillers, plasticizers into the adhesive, and in some cases by heat treatment of the adhesive joint.

The strength of the adhesive bond determined during testing can be significantly affected by the size and design of the test sample (as a result of the action of the so-called edge effect), the thickness of the adhesive layer, the history of the adhesive joint, and other factors. Of course, one can speak about the values of the strength of adhesion or autohesion only in the case when the destruction occurs along the interfacial boundary (adhesion) or in the plane of the initial contact (autohesion). When the sample is destroyed by the adhesive, the obtained values characterize the cohesive strength of the polymer.

Some scientists believe, however, that only cohesive failure of an adhesive joint is possible. The observed adhesive nature of the destruction, in their opinion, is only apparent, since visual observation or even observation with an optical microscope does not make it possible to detect the remaining thinnest layer of adhesive on the surface of the substrate. However, in recent times Both theoretically and experimentally, it was shown that the destruction of an adhesive joint can be of the most diverse nature - adhesive, cohesive, mixed, and micromosaic.

With this process of adhesion, the attraction of different types of substances at the molecular level is carried out. It can affect both solids and liquids.

Determination of adhesion

The word adhesion in Latin means adhesion. This is the process by which two substances are attracted to each other. Their molecules stick together. As a result, in order to separate two substances, it is necessary to produce an external effect.

This is a surface process, which is typical for almost all systems of the dispersed type.

Adhesion - what is it? Adhesion: definition

This phenomenon is possible between such combinations of substances:

liquid + liquid,
solid body+solid body,
liquid body + solid body.

All materials that begin to interact with each other during adhesion are called substrates. Substances that provide substrates with tight adhesion are called adhesives. For the most part, all substrates are represented by solid materials, which can be metals, polymeric materials, plastics, ceramics. Adhesives are predominantly liquid substances. good example adhesive is a liquid such as glue.

This process may result in:

mechanical impact on bonding materials. In this case, in order for the substances to hold together, it is necessary to add certain additional substances and use mechanical methods clutch.
interactions between molecules of substances.
Formation of an electric double layer. This phenomenon occurs when an electrical charge is transferred from one substance to another.

Currently, there are not rare cases when the process of adhesion between substances appears as a result of the influence of mixed factors.

Adhesion strength

Adhesion strength is a measure of how tightly certain substances adhere to each other. To date, the strength of the adhesive interaction of two substances can be determined using three groups of specially developed methods:

Separation methods. They are further subdivided into many ways to determine the adhesive strength. To determine the degree of adhesion of two materials, it is necessary to try, using an external force, to break the bond between the substances. Depending on the bonded materials, the simultaneous tear-off method, or the sequential tear-off method, can be used here.
A method of actual adhesion without interfering with a structure created by bonding two materials.

Using different methods different indicators can be obtained, which largely depend on the thickness of the two materials. The peeling speed and the angle at which separation is to be carried out are taken into account.

Adhesion of materials

AT modern world meet different kinds adhesion of materials. Today polymer adhesion is not a rare occurrence. When mixing different substances, it is very important that their active centers interact with each other. At the interface between two substances, electrically charged particles are formed, which provide a strong connection of materials.

Glue adhesion is a process of attraction of two substances by mechanical interaction from the outside. Glue is used to stick two materials together to create one item. The bonding strength of materials depends on the strength of the adhesive in contact with certain types of materials. To bond materials that do not interact well with each other, it is necessary to increase the effect of the adhesive. To do this, you can simply use a special activator. Thanks to it, strong adhesion is formed.

Very often in the modern world we have to deal with the bonding of materials such as concrete and metals. The adhesion of concrete to metal is not strong enough. More often in construction, special mixtures are used that provide reliable bonding of these materials. Also, building foam is often used, which forces metals and concrete to form a stable system.

Adhesion Method

Adhesion methods are methods by which it is established how different materials can interact with each other within a certain specificity. Various building objects and household appliances are created from materials that are fastened together. In order for them to function normally and do no harm, it is necessary to carefully control the level of adhesion between substances.

Adhesion measurement is carried out using specialized devices that allow at the production stage to determine how firmly the products are attached to each other after using certain bonding methods.

Adhesion of paints and varnishes

The adhesion of paint and varnish coatings is the adhesion of paint to various materials. The most common adhesion of the paint and varnish substance and metal. In order to cover hardware a layer of paint initially tests the interaction of two materials. It is taken into account with what layer it is necessary to apply a paint and varnish substance in order to determine its degree of adsorption. Subsequently, the level of interaction between the ink film and the material with which it is coated is determined.

adhesive property

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The adhesive properties are characterized by the normal pull-off stress p of two solid surfaces brought into interaction. An increase in the adhesion force increases the intensity of granule formation, but makes it difficult to work with the material due to its sticking to the walls of the apparatus. Ceteris paribus, /ad depends significantly on the concentration of the binder, and this dependence is of an extreme nature.

The adhesive properties of adhesives of plant and animal origin are inextricably linked with their chemical nature. However, in some cases it is difficult to identify a direct relationship between the chemical nature of the adhesive and the substrate when gluing wood, not only because of the complexity of the chemical nature of wood, but also because it is subject to more significant changes than the adhesive layer. For example, under conditions of high humidity and high temperatures, wood deforms due to swelling and shrinkage. Besides, wooden structures and products illuminated by sunlight absorb radiant energy and heat up to a temperature much higher than the ambient temperature. The temperature in the plywood skin of an aircraft, for example, can reach 90 C.

Adhesive properties play an important role in the functioning of dressings.

On the one hand, the bottom layer of the dressing should be easily wetted, ensuring a tight fit of the dressing to the wound, on the other hand, the surface energy at the dressing-wound interface should be minimal to ensure the least trauma when it is removed from the wound.

Adhesive properties sometimes have a decisive influence on the choice of method and conditions for the manufacture, storage, use and transportation of powder. different materials.

The adhesive properties of various high-strength and heat-resistant enamels are approximately the same and significantly higher than those of PEL and PELU wires. When testing by twisting, samples 50 mm long in accordance with GOST 7262 - 54 must withstand, depending on their dimensions, at least 7 - 17 twists. In fact, these tests often give better results. Thus, wires of the PELR-2 brand with a diameter of 0 55 - 1 20 mm often withstand up to 30 - 24 twists.

The adhesive properties (stickiness) of synthetic adhesives have not yet been studied enough, but scientists suggest that they depend on at least two main factors: the flexibility of the macromolecule units and the presence of polar groups in it.

The adhesive properties of various high-strength enamels are approximately the same and significantly higher than those of PEL and PELU wires. When tested by twisting, samples 50 mm long, in accordance with the standard, must withstand, depending on their dimensions, at least 7 - 17 twists. In fact, these tests often give better results. So, when testing wires PELR-2 with a diameter of 0 55 - 1 20 mm, the samples often withstand up to 30 - 24 twists.

The adhesive properties of some film-forming materials depend on their plastic properties. Since shrinkage of film-forming materials occurs during hardening, the stresses developing between the film and wood can lead to a significant weakening of the bond between the coating and wood - their lagging, and in brittle coatings - to cracking. Therefore, plasticizers are introduced into many paints and varnishes, which increase the plastic properties of the coating. An increase in the thickness of the lacquer film adversely affects the adhesive properties of coatings due to an increase in shrinkage stresses.

Adhesive properties can manifest themselves only in a monolayer of particles deposited on the walls or filter surfaces of gas cleaning devices, and due to the very small thickness of such a layer, as a rule, they do not affect the operation of dust and ash collection systems.

Adhesion of concrete to concrete: how, what and why?

The adhesive properties of paraffin are most strongly enhanced by atactic polypropylene and oxidized petrolatum, while their combined presence gives a synergistic effect.

The adhesive properties of dusts characterize the tendency of dust particles to stick together, which affects the performance of dust collectors.

The adhesive properties of substrates can be changed by grafting. Grafting is carried out using high energy sources or in electric field.

The adhesive properties of bitumen make it a valuable material for the manufacture or fastening of many products.

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There are many types of fastening: welding, rivets, connection with fasteners and so on. However, the use of an adhesive composition remains one of the most popular, as it allows you to connect the surfaces of very different materials and without mechanical impact on objects.

Glue laying

One of the fundamental selection factors in this case is the high adhesion of the adhesive.

What it is

Gluing is a method of permanent connection of any elements, due to the formation of an adhesive bond between the surfaces to be glued. The composition used for this is called glue. A substance can be of natural or artificial origin, but in any case it must have certain properties.

Adhesion is a property that ensures the strength of the connection of materials. After the adhesive layer has hardened, the objects should form, as it were, a single whole. If the connection cannot be separated, we can talk about the high adhesive properties of the substance.

Preparation of the adhesive

This quality indicates the ability of the adhesive composition to gain a foothold on the surface. Thus, the metal is a low-porosity substance, which indicates its low adhesive properties. regular glue, for example, on the surface of metal or glass simply will not hold.

Adhesion - what is it in construction

Adhesive with enhanced adhesive properties forms a bond strong enough to bond smooth surfaces.

What is cohesion? The strength that the glue itself provides when it hardens. For example, plasticine can temporarily hold two objects together, but under the weight of one of them, the material is easily destroyed. Adhesive composition with good cohesion ensures bond strength.

This value is relative, as it depends on the nature and weight of the objects being glued. So, the label attached to the bottle has a minimum weight, and to keep it, a mixture with rather low cohesive qualities is enough. But tile adhesive with adhesion to concrete should have increased cohesion, since the tile is a heavy product.

Mixing mortar for tiles

Another important parameter composition - the ability to maintain the strength of the connection at different temperatures. In everyday life, mixtures are used that provide a setting when normal temperature, that is, about 20–30 C. However, already in construction work, when fixing stone and ceramics, when fixing metal panels and bricks, this is not enough. Release different types products designed for operation at different temperatures.

Adhesion, cohesion, temperature operating range of the product is regulated by GOST.

The essence of gluing

Regardless of the nature of the adhesive mixture, its mechanism of action is the same and is determined by 2 main factors.

Glue with good adhesion - tile, for metal surfaces, and so on, is supplied to the consumer in a semi-finished form. Its components are mixed, but have not entered into a final reaction. When preparing the composition - mixing and mixing of dry components with water occurs chemical reaction, and the substance begins to polymerize. In this case, the pasty product slowly or quickly turns into a solid state.

In everyday life, this process is called setting or hardening. It is known that it is possible to glue materials only while the mixture is in a semi-liquid state.

Glue application

The affinity of materials - it is clear that substances similar in nature have high adhesion to each other, the only exception is metals. Both ceramic products - tiles, porcelain stoneware, and concrete are complex compounds, they include quite a lot of various components. If the solution connecting them has a similar composition, its adhesive properties with respect to these materials will be increased. So, for laying tiles on concrete and brick bases, compositions that include cement are most often used.

How to choose a high adhesion adhesive for tiles

There are quite a few factors to take into account:

Operating conditions - when it comes to exterior decoration, it is clear that ceramics will be exposed to low temperatures, and, therefore, it makes sense to use only good special compound frost resistant. When it comes to facing the fireplace, the situation is the opposite - you need a material that can withstand the action of very high temperatures.
In addition, humidity must also be taken into account. For a damp room, you will need an adhesive that is elastic. In the photo - samples of good adhesive mixtures.
Affinity for the base - concrete, brick, cement-sand binders are considered a simple base for ceramic finishing, since, firstly, they themselves are quite porous materials, and, secondly, they include many components such as cement, mineral filler, and so on. For connection with metal or glass surfaces, only specialized mixtures are used, with increased adhesion in relation to low-porous materials.

Cement adhesive for tiles

Adhesion of adhesive for tiles is regulated by GOST. If we are talking about a porous version, then ordinary mixtures are used, even cement ones. When it comes to low-porous materials, a special solution is required. For example, porcelain stoneware and clinker fall into this category, for example, since their porosity is very low and the usual cement tile composition does not hold the product on the wall.

GOST 31357-2007

It is used for laying heavy large-format slabs and slabs of medium size and weight made of marble, natural and artificial stone for indoor and outdoor work. The maximum weight of glued boards is not more than 100kg/m2 of surface.

GLUE recommended for outer cladding bases subject to increased operational loads: plinths, columns, external stairs, basements, indoor areas with normal and high humidity: for bathrooms, balconies and terraces.

Coating adhesion

Ideal for tiling difficult substrates such as old tiles, heated surfaces, etc.

For interior and exterior use
For children's and medical institutions
Impact and crack resistance
Application when facing "complex" bases
Laying slabs using the "top-down" method
Use in the system "Warm floor"

Characteristics

Working temperature
The amount of water per 25 kg. dry mix
Layer thickness
Consumption when working with a spatula 6X6
Solution pot life
Tile laying time
Tile position adjustment time
Hardening time
Adhesion strength to the base
Tile holding weight
Frost resistance	at least 35 cycles
Operating temperature	from -50 to +70°C
Package

GLUE has increased strength characteristics, which allows it to be used when laying heavy slabs and operate in harsh conditions. The high adhesive power allows for top-down cladding.

GLUE is used on heated surfaces (up to +70C), including in the "Warm floor" system.

The plasticity of the finished solution makes the adhesive easy to use. After hardening, the adhesive retains its properties in direct contact with water and when exposed to negative temperatures.

GLUE is an environmentally friendly material. does not emit substances hazardous to human health and the environment during the production of work and operation.

The term "adhesion" is often found in documents in various scientific disciplines. It is used in physics, chemistry, and biology. However, each science has its own approach to what adhesion is, the definition of which, taking into account all the facets of the phenomenon, cannot yet be given by any scientist. True, everyone agrees on one thing: it is a connection, an interaction of various particles.

If we consider it as a process, we can say that adhesion is a phenomenon that consists in the appearance of interaction between some condensed phases. When their molecular contact occurs, this interaction leads to the emergence of a new heterogeneous entity.

If this phenomenon is understood as a property, then adhesion is (in the case of liquids) the interaction between the liquid and solid phases at their interface.

Physics

From the standpoint of physics, adhesion is the adhesion of surfaces of various substances when they come into contact. Moreover, substances can be both in the same and in a different state of aggregation. Thus, the effect may concern two solids, two liquids, or a liquid and a solid.

Substances adhere under the influence of the following factors:

chemical bonds between the molecules of two substances
diffusion occurs when the molecules of the first substance penetrate the boundary of the surface of the second,
van der Waals forces act, which arise when polarization of molecules occurs.

There are still special cases when adhesion can occur. They are often confused. These are autohesion and cohesion.

Autohesion occurs as a result of the adhesion of homogeneous bodies, however, the phase boundary is preserved.

Cohesion can occur when molecules of the same body interact.

AT natural conditions there are cases when adhesion due to various external causes becomes cohesion. Such a situation arises during diffusion if the phase boundaries become blurred. In some cases, the strength of the adhesive bond between the phases may be greater than the cohesive one. Then, depending on the strength of the substance, when a force is applied to the connection of substances, the interface is preserved or the cohesive bonds are broken.

Chemistry

Chemistry has a vision of the adhesion process similar to physics. Many technological processes in the chemical industry have adopted practical use of this phenomenon. It is this that underlies the manufacturing technology. composite materials, and production is also based on it paintwork materials. The concept of adhesion in chemical science is used when talking about the process of gluing surfaces in the solid state with an adhesive (substrates are glued together with an adhesive).

Biology

In biological science, the term is used not in relation to molecules, but in relation to relatively large biological particles - cells. Adhesion is such a connection of cells that allows the formation of histological structures correctly, and the type of these structures is determined by the specifics of the cells involved in the interaction. The result of the interaction depends on the presence of certain proteins on the surface of the connecting cells.

Effect on material properties

Adhesion has the ability to significantly change the characteristics of the surfaces that come into contact. It can help surfaces acquire a low coefficient of friction. If, in this case, the substances have a solid crystalline structure, then it becomes possible to further use them as anti-friction lubricants. Effects such as capillarity and wettability also occur due to this phenomenon.

unit of measurement

When adhesion occurs, the energy of the body on some part of the surface instantly becomes less. For this reason, it is customary to measure it by the work or force required to tear the surfaces apart on a certain unit area.

Application of adhesion in construction

Such a physical phenomenon as adhesion contributed to the improvement technological process manufacturing of steel plates and blocks having thin and thick walls. Possession of information about the mechanisms of the phenomenon made it possible to increase the productivity of the lines for the manufacture of these building products and significantly reduce the weight of structures.

Only this phenomenon makes it possible to paint and varnish the surfaces of building materials, apply galvanic and anodic coatings. These operations contribute to the creation of anti-corrosion protection of the metal, giving the material a marketable appearance.

Knowledge of the nature of the phenomenon is of great help in high-quality gluing of various materials and their strong welding. With the participation of adhesion, metals are coated with oxide films that perform protective functions. The effect is used in the production of concrete works - in situations where it is not possible to immediately achieve a complete pouring of the object with concrete. When refilling, two concrete bases form the so-called cold joint, negatively affecting the strength characteristics of the connection. Adhesion is also recommended for applications where it is necessary to separate concrete from steel moulds. In other ways, this operation is simply impossible to perform. The use of adhesion makes it possible to successfully deal with surface defects finished products from concrete.

cement mortars

The division of adhesive mortars with the participation of cement into classes C1 and C2 is based on an assessment of the degree of adhesion of the mortar to the base after hardening. Adhesion of class C1 adhesive solution to the substrate according to requirements European standards quality should be more than 0.5 MPa, while for cement adhesive solution class C2, its value is not less than 1.0 MPa. Thus, the difference between the two classes of solutions determines the adhesion strength.

Methods for determining adhesion

Methods by which adhesion is determined (GOST 15140-78):

flaking;
lattice cuts;
lattice cuts with reverse impact;
parallel cuts.

Adhesion in metallurgy

During adhesion, the phase boundary between the bodies is preserved. The adhesion of metals finds its manifestation when non-metallic inclusions are coagulated in the composition of liquid metals and alloys. Adhesion contributes to the enlargement of non-metallic inclusions, which subsequently leads to their removal from the metal into the slag.

The effect of adhesion or wetting of non-metallic inclusions with liquid metal can:

interfere with the extraction of inclusions from the metal if the metal melt wets the non-metallic inclusions well (in this case, good adhesion takes place);
create conditions for the removal of non-metallic inclusions from the metal in a situation where these inclusions are not sufficiently wetted by the metal melt (in this case, the adhesion value is small).

During cold welding, almost all hard metals that are in a plastic state are joined under pressure. Adhesion underlies the adhesion of galvanic, oxide, sulfide coatings to metal, which are applied to the metal surface in order to protect products from corrosion. The adhesion of the coating ensures its reliable adhesion of such compositions to the surface of metals. It has found its application in powder metallurgy, when products are formed and sintered from metal powders.

Adhesion of materials is widely used in cases where it is necessary to solder, tin, zinc, apply a variety of paint and varnish coatings. Without it, the creation of various composite materials is not complete. In the manufacture of such materials, particles of a substance come into contact with the base of the alloy. The effect increases in the presence of an electric charge on the surfaces of the bodies, which makes it possible to form a donor-acceptor bond upon connection. Adhesion is also enhanced when carrying out chemical cleaning connected surfaces. For these purposes, degreasing, vacuuming, ion bombardment, and exposure to electromagnetic radiation are used.

Adhesion activator

When a car is in operation, the smallest pores on the surface of the paint layer and polymer parts become clogged with residues of dust, tar, auto chemicals. As a result, an attempt to glue something on the parts often ends in failure due to poor adhesion of the surface. Degreasing does not eliminate all contaminants. Adhesion activator is designed for use in preparing surfaces before applying decorative films, stickers, nameplates, double-sided tape. The activator significantly increases the adhesive properties of surfaces due to a specially developed composition. Its use ensures that the bonding is reliable and allows the materials to be joined to be used for a long time. The high adhesion provided by the activator is the reason for the high demand for it.

Definition of the concept of adhesion. Classification of adhesive compounds in dentistry. Mechanisms for the formation of adhesive compounds. Conditions for the formation and nature of the destruction of adhesive joints.

Adhesion- this is a phenomenon that occurs when dissimilar materials are brought together in close contact, for the separation of which it is necessary to apply force. When two materials are brought into such close contact with each other that their surface monomolecular layers can interact, the molecules of one substance interact in a certain way with the molecules of the other, experiencing mutual attraction. The forces of this attraction are called adhesion forces or adhesive forces. Unlike cohesive forces(cohesive forces), which determine the mutual attraction of the molecules of the same substance in its volume.

The material or layer that is applied to form an adhesive bond is called an adhesive. The material on which the adhesive is applied is called the substrate.

Adhesion is found in many applications of restorative materials in dentistry. For example, when connecting a filling with the walls of a tooth cavity, sealant and varnish with tooth enamel. When fixing fixed dentures with cements. In orthodontics, braces are attached to the surface of the teeth on the principles of adhesion. Adhesion is also present in combined prostheses, in which they seek to give aesthetic and functional properties to the restoration, namely, when using porcelain and metal in ceramic-metal prostheses, plastic and metal in metal-plastic prostheses.

Scheme 3.1 shows the classification of adhesive compounds used in dentistry.

Scheme 3.1. Classification of types of adhesive compounds in dentistry

It should be emphasized that there is a significant difference between the adhesive compounds of restorative materials with tissues of a living organism and compounds of dissimilar materials that are used in dentures.

There are several mechanisms for the formation of an adhesive joint due to various types of adhesive bonds (the classification of types of adhesive bonds is given in Scheme 3.2).

Mechanical adhesion consists in wedging of the adhesive in the pores or surface irregularities of the substrate. It can occur on a microscopic level, as in the case of bonding a polymer to etched tooth enamel, or on a macro level, when a plastic veneer is applied to the surface of a metal frame that has special grips. good example mechanical adhesion can be the fixation of fixed dentures with an inorganic cement, such as zinc phosphate cement.

A stronger and more reliable connection can be achieved using chemical adhesion. It is based on the chemical interaction of two materials or phases that make up an adhesive bond. This type of adhesion is inherent in aqueous cements on polyacrylic

Scheme 3.2. Types of adhesive bonds*

acid, which contains functional groups, capable of forming a chemical compound with hard tissues of the tooth, primarily with calcium hydroxylapatite.

A diffusion bond is formed as a result of the penetration of the structural phase or components of one material into the surface of another with the formation of a "hybrid" layer, which contains both phases.

In practice, it is difficult to find a case of an adhesive joint in which any of the listed adhesion mechanisms would be presented in a pure form. In most cases, when using materials of various chemical nature for tooth restoration, there is an adhesive interaction of mechanical, diffusion, and chemical nature.

Conditions for creating a strong adhesive bond:

1. The cleanliness of the surface to which the adhesive is applied. The surface of the substrate should be free of dust, foreign particles, adsorbed moisture monolayers and other contaminants.

2. Penetration (penetration) of the liquid adhesive into the surface of the substrate. Penetration depends on the ability of the adhesive to wet the surface of the substrate.

Wetting characterizes the ability of a liquid drop to spread on a solid surface. A measure of wetting is the contact angle of wetting (Θ), which is formed between the surfaces of liquid and solid bodies at their interface (Fig. 3.1).

*Based on WJ classification. O "Brien "Dental Materials and Their Selection", Quintessence Publ. Co., Inc, 3rd ed., p. 66.

Rice. 3.1. contact angle

With complete wetting, the contact angle is 0°. Small values of the contact angle characterize good wetting. With poor wetting, the contact angle is greater than 90°. Good wetting promotes capillary penetration and indicates a strong mutual attraction of molecules on the surfaces of the liquid adhesive and the solid substrate.

Formation of the strong chemical bonds at the interface will significantly increase the number of places of attachment of one material to another. It is assumed that this is exactly what happens between porcelain cladding and tin oxide deposited on the surfaces of alloys with great content noble metals.

3. Minimum shrinkage and minimum internal stresses during hardening (curing) of the adhesive on the surface of the substrate.

4. Minimum possible thermal stresses. If the adhesive and substrate have different coefficients of thermal expansion, then when this connection is heated, the adhesive line will experience stress. For example, a porcelain veneer is applied to a metal frame during the porcelain firing process at high temperature, and then the ceramic-metal prosthesis was cooled to room temperature. If materials with similar coefficients of thermal expansion are selected for this pair, then the stresses arising in this case in the porcelain layer will be minimal.

5. Possible impact corrosive environment. The presence of water, corrosive liquids or vapors often leads to poor adhesion. The environment of the oral cavity with its high humidity, the presence of saliva, food products, variable pH, variable temperature and the presence of microflora is recognized as aggressive. This has a significant impact on the reliability and durability of adhesive joints of restorative materials in the oral cavity.

Adhesion is usually judged by the value of adhesive strength, i.e. resistance to destruction of the adhesive joint. As follows from the definition of adhesion, it is sufficient to measure the applied force to separate the materials that make up the adhesive pair in order to determine the strength of this connection. However, it is not so easy to achieve that the measured force of separation of the glued pair numerically corresponds precisely to the adhesive strength. Therefore, so many methods have been proposed for measuring various adhesive bonds used in dentistry. With all the variety of options, they contain only three failure mechanisms: in tension, shear, and uneven separation.

When testing an adhesive joint, attention must be paid to the nature of the destruction. There are adhesive (adhesive separation) and cohesive destruction. It is obvious that the fracture surface passes through the weakest link of the connection.

is the bond between dissimilar surfaces brought into contact. The reasons for the emergence of an adhesive bond are the action of intermolecular forces or chemical interaction forces. Adhesion determines the bonding of solids - substrates - with the help of an adhesive - adhesive, as well as the connection of a protective or decorative paintwork with the base. Adhesion also plays an important role in the dry friction process. In the case of the same nature of the contacting surfaces, one should speak of autohesion (autohesion), which underlies many processes for the processing of polymeric materials. With prolonged contact of identical surfaces and the establishment in the contact zone of a structure characteristic of any point in the volume of the body, the strength of the autohesive connection approaches the cohesive strength of the material (see cohesion).

On the interfacial surface of two liquids or a liquid and a solid, adhesion can reach an extremely high value, since the contact between the surfaces in this case is complete. The adhesion of two solid bodies due to surface roughness and contact only at certain points is usually small. However, high adhesion can also be achieved in this case, if the surface layers of the contacting bodies are in a plastic or highly elastic state and are pressed against each other with sufficient force.

Liquid adhesion

Adhesion of a liquid to a liquid or a liquid to a solid. From the point of view of thermodynamics, the cause of adhesion is a decrease in free energy per unit area of the adhesive joint in an isothermally reversible process. Work of reversible adhesive detachment Wa is determined from the equation:>Wa = σ1 + σ2 - σ12

where σ1 and σ2 are the surface tension at the interface between phases 1 and 2, respectively, with the environment (air), and σ12 is the surface tension at the interface between phases 1 and 2, between which adhesion takes place.

Methods for determining adhesion

The method of simultaneous separation of one part of the adhesive joint from the other over the entire contact area;
The method of gradual delamination of the adhesive joint.

Pull-off method - adhesion

Peeling Method - Adhesion

Adhesion test methods

However, during curing, drying, and polymerization, the adhesive typically shrinks, resulting in tangential stresses at the interfacial surface that weaken the adhesive bond.

These stresses can be largely eliminated by introducing fillers, plasticizers into the adhesive, and in some cases by heat treatment of the adhesive joint.

COHESION (from lat. cohaesus - connected, linked * a. cohesion; n. Kohasion; f. cohesion; and. cohesion) - adhesion of particles of matter (molecules, ions, atoms) that make up one phase. Cohesion is due to the forces of intermolecular (interatomic) attraction of various nature

When carrying out certain types of work, it is necessary to determine the level of interaction of certain elements. It is important to initially know how strongly they adhere to each other so that the structure is as reliable as possible.