Adhesion wiki. Adhesive systems and adhesion in dentistry. Adhesive properties of building and finishing materials
S. A. Nenakhov (NPO NEOHIM, Moscow)
Terms related to adhesive adhesives cannot be classified as neologisms. Thus, the term adhesion was introduced in 1924 by Behold and Neumann to designate specific molecular adhesion in addition to the then prevailing ideas about the mechanical nature of the nature of bonding. The appearance of the term glue in Russian vocabulary is attributed to XII century. Nevertheless, even today it cannot be said that these terms are characterized by specialization of meaning and semantic precision, even when used in scientific literature.
The ambiguity and uncertainty of the term glue and words and phrases derived from this term found in publications and regulatory and technical documents is mainly due to the well-known terminological sloppiness of the authors, i.e. this is a matter of language culture and, perhaps, lexicography. Common adhesive terms are presented below.
As for the term adhesion, the ambiguity and uncertainty of this term is reminiscent of the confusion and confusion that reigned in XVII-XVIII centuries in the fundamental concepts of the theory of heat until the invention and use of the thermometer made it possible to clearly distinguish between the concepts of temperature and quantity of heat. Based on an acceptable analogy with past difficulties in the formation of the conceptual apparatus of thermodynamics, we can assume that in the issue of adhesion we are dealing not so much with the problem of lexical agreement (conventionalization) in the scientific community, but with a methodological problem, or more precisely, with an axiomatic problem.
The methodological problem was expressed quite dramatically for its time by S.S. Voyutsky, who wrote that existing theories of adhesion consider different cases and different aspects of this phenomenon, and “... there is no single theory that explains the phenomena of adhesion and, probably, there cannot be. In different cases, adhesion is determined by different mechanisms...”. Indeed, at least five theoretical approaches to the adhesion mechanism were available by the end of the 70s of the last century: electrical theory, adsorption theory, diffusion theory, mechanical theory and weak boundary layer theory. An attempt to formally combine these theories was made by K.V. Alain.
The numerous definitions of adhesion existing in the literature based on semantic features can be divided into three groups. The first group includes formulations that define adhesion as a process (sequential change of states). To the second - defining as a property (quality, sign) that makes up distinctive feature systems. The third - defining as the state (external or internal circumstances in which something is located) of the system. Below are typical examples definitions.
Adhesion as a process
"Adhesion (sticking) is the formation of a connection between surface layers two dissimilar (solid or liquid) bodies (phases) brought into contact" (P. A. Rebinder).
“Adhesion is a phenomenon consisting in the occurrence of physical and/or chemical interaction between condensed phases during their molecular contact, leading to the formation of a new heterogeneous system” (V.L. Vakula, L.M. Pritikin).
“Adhesion is the phenomenon of joining surfaces of condensed phases brought into contact” (L. M. Pritykin, V. L. Vakula).
Examples of this approach can be multiplied. It can be seen that here adhesion is interpreted as a process in a system of two condensed phases when they approach each other (from an infinite distance) to the distance of action of intermolecular forces, as a result of which a bond arises between dissimilar condensed phases. It must be said that terms with a similar grammatical structure, etymologically dating back to Latin roots, indeed primarily designate certain processes, for example, adsorption, diffusion, sorption, etc. In order not to be unfounded, we will give an example from “Physical encyclopedic dictionary": "Diffusion is the process of establishing an equilibrium distribution of concentrations within phases..." In contrast, phonetically similar terms of Greek origin, for example, "energy" and "entropy" denote a certain measure. Thus, about this " process approach“We can say that here the semantic meaning of the term and its grammatical form correspond to each other. But, on the other hand, phrases like the expression “kinetics of adhesion formation” are also understandable to us and do not cause irritation.
Adhesion as a property
“Adhesion is understood as a molecular bond between the surfaces of dissimilar bodies brought into contact” (A.A. Berlin, V.E. Basin) [Yu, 11].
“Liquid adhesion means the interaction of liquid and solid phases at the interface between these phases” (A.D. Zimon).
“Adhesion, sticking... - the connection between dissimilar surfaces brought into contact” (S.S. Voyutsky).
B.V. Deryagin and his colleagues made an attempt to eliminate the problem by separating the process and the property: “It is generally accepted that adhesion, in contrast to cohesion, means resistance to breaking the contact of two dissimilar bodies. Therefore, adhesion phenomena are naturally attributed to surface phenomena controlled by surface forces. To eliminate the ambiguity, it would be advisable the term “adhesion” refers to the processes of establishment and progressive growth over time of a molecular connection between two bodies, while the term “adhesion” is used to denote the achieved strength of this connection. Thus, adhesion, in accordance with the etymological basis of the word, should denote a process, and adhesion - a quantitative one. measure of its result." Note that from an etymological point of view, only the first part of the last sentence in the quotation is valid.
Similar definitions in the same years appear, for example, in English-language literature: S. Wake, L.-H. Lee. A. Adamson, trying to limit the ambiguity of the term, proposed in a narrow sense “by adhesion we understand the strength of the bond between two contacting phases.”
Adhesion as a state
“Adhesion is a condition of two dissimilar bodies in which they are held together in close interfacial contact in such a way that mechanical force or work can be transferred across the interface” By Shouheng). Let us note that English-language authors were the first to overcome the framework of the grammatical structure of the term in this direction. The above definition expands the interpretation of the term to a new semantic meaning - the state of two dissimilar bodies. What is special about this condition? According to the author's proposal, there is interphase contact between these dissimilar bodies. Such contact that mechanical work can be transferred across the interface. Possibility of transfer mechanical work across the interface means the presence of interaction (force of attraction, attraction) between the phases, i.e. this definition, the accentuating state, in fact, returns us to the same object - the interphase boundary and to the same interphase interaction.
Let's summarize. In all three groups of definitions, we are talking about the same object - a heterogeneous body consisting of two dissimilar condensed contacting phases, while the bodies are connected across the interface by intermolecular forces. The difference between these groups of definitions is that in the first group of terms the emphasis is on the process of the emergence of a connection or the transition of the system to a new state - connected, in the second group - on the actual presence of a connection, a measure of the result. Finally, in the third group, the emphasis is on the state (there is a connection, there is no connection) and the process is ignored.
In modern terminography, unfortunately, there is no single point of view regarding the admissibility of such ambiguity. Experts of one school believe that unambiguity is an indispensable feature of the term. Others - that the polysemy of a term is not proof of the vagueness of linguistic concepts, i.e. We cannot rely on terminography. In such a situation, the easiest thing is to leave everything as it is, since it is usually clear from the context what is being said. Pedants will prefer a process approach, but time will put everything in its place, and terminology will find an explanation for this.
It seems to us that the main difficulty lies not so much in the ambiguity of the given definitions - they are all about different aspects of the same phenomenon, but in the variety of objects and phenomena that they try to subsume under this definition and consider as adhesive phenomena, which leads to ambiguity.
For example, what about the many theories explaining the mechanism of adhesion? Is the fate of adhesion really so sad that this phenomenon cannot be described by a single theory? Without pretending to provide a detailed consideration of the entire issue, or even a detailed consideration of the axiomatics of adhesion, we will only suggest here that the number of adhesion theories can be significantly reduced if we limit the usually considered range of objects only to those that are actually discussed in the considered definitions. Thus, if in the definition of adhesion we clarify, limit the concept of an object, namely, abandon the amorphous phrase “dissimilar bodies (phases)” in favor of the specific “phases incompatible in the thermodynamic sense,” then some theories classified as adhesive will fall out of the range of adhesion problems .
For example, diffusion theory. The objects and phenomena described in the diffusion theory really exist, but these are compatible systems without equilibrium interphase boundaries, these are systems that are characterized (in the limit) by the disappearance of the interface, therefore, strictly speaking, they cannot be classified as objects considered in all three the above groups of definitions. Of course, diffusion processes determine a lot in the behavior (kinetics, equilibrium properties) of compatible systems. But these phenomena are not related to adhesion, but rather to the theory of autohesion or cohesion.
The mechanical theory of adhesion actually considers systems with various kinds mechanical gears, the description of the behavior of which under mechanical loading has theoretical and practical meaning, but the mechanical gears themselves are not related to intermolecular forces. Of course, mechanical engagements are also possible in real adhesive joints. Their contribution to mechanical strength may even exceed the adhesive contribution itself, but this problem rather relates to taking into account the properties of deformable macrobodies, i.e., to theoretical mechanics. In accordance with the mechanical theory of adhesion, puzzles should also be classified as adhesive objects.
Weak boundary layer theory. Nowadays, it is clearly understood that near the phase boundary, a restructuring of the structure of the body occurs. The extent of these regions can reach several tens of micrometers, and the regions themselves are characterized by a different degree of molecular packing than the body in volume. According to this theory, the destruction of a body occurs along the so-called weak layer, which, as a rule, is localized outside the actual phase boundary. The formation of this layer is a consequence of the action of intermolecular interaction forces between phases, i.e. secondary to the formation of bonds at the interface of incompatible phases. IN real systems different degrees of defects in interphase layers can significantly affect the results, for example, of mechanical tests, but this circumstance is neither necessary nor sufficient for classifying the theory of a weak boundary layer as a theory of adhesion. Rather, this theory should be classified among theories that explain deviations from “ideal” adhesion.
Thus, if we proceed strictly from the considered definitions of adhesion, then we can state that a single object in the definitions of adhesion exists - this is the interphase boundary of contacting incompatible phases. Another thing is that to describe this subject (phenomenon) there are different approaches, for example, thermodynamic. Or in the form of molecular theories of interaction between macroscopic bodies, for example, a theory based on van der Waals forces, a theory based on the Lenard-Jones potential, or the Livshits theory, which considers electromagnetic waves emitted by bodies. These theories are presented in sufficient detail in a number of monographs, for example, in. Other theories (mechanical and the theory of a weak boundary layer) are appropriate to be considered as corrections that take into account deviations (sometimes significant) from ideal adhesion.
The polemic nature of the approach presented here against the backdrop of historically established ideas is obvious. But it seems to us that the system of the stated restrictions (one of the requirements of the axiomatics) follows from all the considered definitions of adhesion. Restrictions on objects and phenomena can help separate secondary phenomena from primary ones, and help classify phenomena of a different, non-adhesive nature into “their niche.” This will mean the construction of a unified and consistent axiomatics of adhesion and the elimination of the terminological ambiguity that exists today.
Dictionary
Adhesion (from Latin adhaesio - sticking, English adhesion) - 1) the occurrence of intermolecular interaction between dissimilar condensed phases brought into contact; 2) the established interaction between the phases at the interface and the value characterizing it; 3) a bound state of dissimilar phases (bodies), in which they are held in interphase contact.
Abhesive - a release material that prevents adhesion.
Adhesive (eng. adhesive) - 1) adhesive substance; 2) binder; 3) glue; 4) sticky; 5) sticky; 6) a material that connects other materials to each other by adhesion to their surfaces.
Adhesive (th, -th) - an adjective denoting that an object belongs to adhesion, for example, adhesive strength - the strength of an adhesive connection.
Adherend (eng. adherend) - glued material, substrate.
Autohesion is the connection of like (compatible) materials from the moment they are brought into contact until the diffusion disappearance of the geometric interface.
Glue is a material that connects other materials by adhesion to their surfaces.
Cohesion (English cohesion) - 1) adhesion between the surfaces of two bodies of homogeneous composition that are in contact; 2) connectivity; 3) a property of the body that ensures the connection of its parts.
Stickiness is the resistance exerted by the glue when it is separated from the substrate.
A promoter is an additive to an adhesive (glue) that increases the mechanical strength of adhesive joints.
An adhesive connection is the connection of two substrates (bodies) to each other with a layer of glue.
Substrate is a material on the surface of which glue is applied.
Phase (English phase) - a homogeneous isolated part of the system, separated from other parts by demarcating surfaces.
"Adhesives. Sealants. Technologies" No. 4, 2007
Adhesion, what is it? And why is it important? Let's try to figure it out in our article.
The term adhesion, translated from Latin, means “sticking” and characterizes the property of adhesion of the surfaces of solid or liquid bodies. Quite often characteristics construction compounds, used for plastering and paintwork, are assessed by their adhesive properties.
Bonding of bodies is ensured by an adhesive substance - an adhesive, which is a polymer system. However, polymer can be formed as a result of chemical reactions between the bonded surfaces after application of the adhesive. Non-polymer adhesives are organic substances, which include cements and solders.
The substance on which the adhesive is applied is called the substrate. The depth of penetration depends on the type and parameters of the adhesive, which after hardening cannot be removed without destruction. Adhesion - sticking only upper layers materials. If the process penetrates inside the bodies, then cohesion occurs.
Why is it important?
In construction, adhesion guarantees quality and reliability in almost all types of work. This property is especially important for:
- paints and varnishes, as it ensures their adhesion and retention;
- gypsum and cement sand mixtures, the quality of finishing of which ensures the aesthetics of the premises.
It is important to know: just applied cement mortar concrete does not adhere well to the old one. When working with old concrete, it is necessary to use adhesive multilayer compounds.
Metallurgical production requires the use of special anti-corrosion compounds and mixtures. And, in addition, poor adhesion properties with water are required.
In medicine, for example, in dentistry, adhesion of the filling material and the tooth is necessary to ensure its high-quality protection and sealing.
Briefly about the types
Based on their interaction with surfaces, three adhesion types are distinguished:
- physical;
- chemical;
- mechanical.
The essence of physical agnesia is the electromagnetic interaction of contacting surfaces at the molecular level. Everyone knows that a magnet attracts particles charged with static electricity.
Chemical bond is the interaction of an adhesive with a substrate at the atomic level with the participation of a catalyst. It differs from the physical ability of adhesion of surfaces of materials of different densities.
Mechanical – penetration of the adhesive into the top layer of the contacting surface with subsequent adhesion. This process occurs, for example, when painting or coating various materials.
Note: improve agnesia by measures that ensure adhesion: puttying, priming, degreasing the substrate, grinding.
In addition, conditions that worsen agnesia are excluded. These include the presence of dust, grease or substances that reduce the porosity of the surface.
About measuring the adhesion ability of materials
The basic principle of measuring adhesion is to determine the external force under the influence of which the adhesive bond is destroyed: uniformly, unevenly or with a shift. Test methods have been developed for types of destruction.
Test tests are carried out using an adhesive meter according to international and state level, developed for each method of destruction.
Measurement of paint adhesion is carried out according to international standard ISO 2409 “Method of lattice cuts” using the Adhesimeter RN device.
IN domestic GOST 15140-78 establishes methods for determining adhesion in paint coatings metal surfaces. Regulatory document gives a definition of the essence of each method, a list of equipment for testing, describes the preparation and conduct of tests.
The values of the adhesion indicators of coatings are necessary to determine the labor intensity of the work and ensure the specified strength and reliability. They are especially important in construction, where there are often contacting materials that are heterogeneous in both chemical composition, and according to the conditions of education.
Adhesion meters for determining external force different ways are presented in the instrument-making catalog in the section Devices and equipment for quality control of protective coatings.
What is adhesion or adhesion of materials, see the explanation in the following video:
There are many various ways interactions between physical bodies. One of them is surface adhesion. Let's look at what this phenomenon is and what properties it has.
What is adhesion
The definition of a term becomes clearer if you find out how the word was formed. From Latin adhaesio is translated as “attraction, adhesion, adhesion.” Thus, adhesion is nothing more than the connection of condensed dissimilar bodies that occurs upon their contact. When homogeneous surfaces come into contact, a special case of this interaction occurs. It is called autohesion. In both cases, it is possible to draw a clear phase dividing line between these objects. In contrast, they distinguish cohesion, in which the adhesion of molecules occurs within the substance itself. To make it clearer, let's look at an example from life. Let's take ordinary water. Then we apply them to different parts of the same glass surface. In our example, water is a substance that has poor adhesion. This is easy to check by turning the glass upside down. Cohesion characterizes the strength of a substance. If you glue two pieces of glass with glue, the connection will be quite reliable, but if you connect them with plasticine, the latter will break in the middle. From which we can conclude that its cohesion will not be enough for a strong bond. We can say that both of these forces complement each other.
Types of adhesion and factors influencing its strength
Depending on which bodies interact with each other, certain adhesion features appear. The greatest importance is adhesion that occurs when interacting with a solid surface. This property has practical value in the manufacture of all kinds of adhesives. In addition, adhesion of solids and liquids is also distinguished. There are several key factors that directly determine the strength with which adhesion will occur. These are the contact area, the nature of the contacting bodies and the properties of their surfaces. In addition, if at least one of a pair of objects is carried on itself, then during the interaction a donor-acceptor bond will appear, which will strengthen the adhesion force. Capillary condensation of water vapor on surfaces plays a significant role. Due to this phenomenon, chemical reactions can occur between the substrate and the adhesive, which also increases the bond strength. And if a solid body is dipped into a liquid, then you can notice a consequence that adhesion also causes - wetting. This phenomenon is often used in painting, gluing, soldering, lubrication, rock dressing, etc. To eliminate adhesion, a lubricant is used that prevents direct contact of surfaces, and to strengthen it, on the contrary, the surface is activated through mechanical or chemical cleaning, exposure to electromagnetic radiation or the addition of various functional impurities.
Quantitatively, the degree of such interaction is determined by the force that must be applied in order to separate the contacting surfaces. And in order to measure the strength of adhesion, special devices are used, which are called adhesiometers. The very set of methods for its determination is called adhesiometry.
With this adhesion process, attraction of different types of substances occurs at the molecular level. It can affect both solids and liquids.
Adhesion Determination
The word adhesion translated from Latin means cohesion. This is the process by which two substances are attracted to each other. Their molecules adhere to each other. As a result, in order to separate two substances it is necessary to produce an external influence.
This is a surface process that is typical for almost all dispersed systems. This phenomenon is possible between the following combinations of substances:
- liquid + liquid,
- solid body + solid body,
- liquid body + solid body.
All materials that begin to interact with each other upon adhesion are called substrates. Substances that provide substrates with tight adhesion are called adhesives. For the most part, all substrates are represented hard materials, which may be metals, polymer materials, plastic, ceramic material. Adhesives are predominantly liquid substances. A good example An adhesive is a liquid such as glue.
This process can be the result of:
- mechanical impact on materials for adhesion. In this case, in order for the substances to stick together, it is necessary to add certain additional substances and use mechanical bonding methods.
- the appearance of relationships between the molecules of substances.
- Formation of a double electrical layer. This phenomenon occurs when electrical charge is transferred from one substance to another.
Nowadays, it is not uncommon to encounter cases where the process of adhesion between substances appears as a result of the influence of mixed factors. 
Adhesion strength
Adhesion strength is an indicator of how tightly certain substances adhere to each other. Today, the strength of the adhesive interaction of two substances can be determined using three groups of specially developed methods:
- Tear-off methods. They are further divided into many ways to determine adhesive strength. To determine the degree of adhesion of two materials, it is necessary to try, using external force, to break the bond between the substances. Depending on the materials being bonded, the simultaneous tearing method or the sequential tearing method can be used here.
- A method of actual adhesion without interfering with the structure created by bonding two materials.
Using different methods You can get different indicators, which depend largely on the thickness of the two materials. The speed of peeling and the angle at which separation must be carried out are taken into account.
IN modern world meet different kinds adhesion of materials. Today, polymer adhesion is not a rare phenomenon. 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 the process of attraction of two substances through mechanical interaction from outside. Glue is used to glue two materials together to create one object. The bonding strength of materials depends on how strong the adhesive is in contact with certain types materials. To glue materials that do not interact well with each other, it is necessary to strengthen the action of the glue. 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 fastening 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 ensure reliable bonding of these materials. It is also not rarely used construction foam, which forces metals and concrete to form a stable system.
Adhesion method
Adhesion testing methods are methods that determine how different materials can interact with each other within certain specific limits. Various construction projects and household appliances are created from materials that are fastened together. In order for them to function normally and not cause harm, it is necessary to carefully control the level of adhesion between substances.
Adhesion measurement is carried out using specialized instruments that make it possible to determine at the production stage how firmly the products are attached to each other after using certain bonding methods.
Adhesion of paints and varnishes
Adhesion paint coatings represents the adhesion of paint to various materials. The most common problem is adhesion between paint and metal. In order to coat metal products with a layer of paint, tests of the interaction of two materials are initially carried out. It is taken into account what layer of paint and varnish substance must be applied 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.
Why does paint applied to the surface being painted remain firmly on it after some time? Why does the plaster coating adhere to the base when it hardens? Why is concreting possible in principle? There is only one answer to these questions: it’s all about adhesion - the phenomenon of sticking of two surfaces connected to each other.
What is adhesion
Adhesion determines the possibility of gluing solid bodies using an adhesive composition, as well as the strength of the bond between the decorative or protective coating and the base. The reason for the appearance of an adhesive bond is the influence of molecular forces ( physical adhesion) or chemical interaction forces ( chemical adhesion).
The intensity of adhesion is determined by the peel pressure that must be applied to the coating (plaster, paint, sealant, etc.) in order to tear/separate it from the base.
Thus, this indicator is usually measured in units of specific effort - megapascals(MPa). For example, a peel force value (or stick force, which is the same thing) of 1 MPa means that to separate a coating having an area of 1 mm 2, a force of 1 N should be applied (remember that 1 kg = 9.8 N). The adhesion properties of coatings are their main characteristic, which provides the necessary strength, reliability, and also determines the complexity of working with them.
What affects the adhesive ability of substances used in construction
During the process of setting the working mixture, various processes occur in it, which cause certain changes in its properties. In particular, when shrinkage mortar mixture it is possible to reduce the contact surface with the appearance tensile stresses which will lead to the formation shrinkage cracks. As a result, the adhesion of surfaces is weakened. For example, the clutch of an old concrete surface with new concrete does not exceed 0.9...1.0 MPa, while the adhesion of dry building mixtures(which includes components that initiate chemical adhesion processes) with new concrete reaches 2 MPa or more.
How to improve adhesion
Typically, a set of measures is implemented to improve adhesion: mechanical (grinding), physical-chemical (puttying, priming) and chemical (elastication) treatment of the base surface is carried out. These processes are especially effective in repair and construction work, when the contacting surfaces are heterogeneous not only in their chemical composition, but also in the conditions of their formation.
Important! Fresh alkaline cement mortar always adheres poorly to the surface of old concrete, therefore, when working with old concrete, it is imperative to use multilayer adhesive compounds
How to measure the adhesion ability of materials
GOST 31356-2007 regulates the defining indicators of the adhesion strength of dry construction mixtures to the base. About the sequence test trials materials for their adhesion. The technology for conducting such tests makes it possible to determine the adhesion strength of coatings such as ceramic tiles, various protective coatings, plaster, etc. with base.
To control the quality of work performed, it is convenient to use the adhesion meter of the ONIX-AP NEW system. The range for measuring grasping forces using this device is 0…10 kN. The test measures the force required to separate or lift the coating from the surface of the substrate in a direction perpendicular to the plane of the coating. The convenience of using an adhesive meter lies in the fact that it can be used to operational control quality finishing and plastering works. The device is compact and easy to maintain (see Fig. 1.2,3).
Fig.1. Determination of grip force ceramic tiles using an adhesiometer (step 1)
