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Model plaster. Gypsum as a building and finishing material

Gypsum- mineral, aqueous calcium sulfate. The fibrous variety of gypsum is called selenite, and the granular variety is called alabaster. One of the most common minerals; the term is also used to refer to the rocks he composed. Gypsum is also commonly called a building material obtained by partial dehydration and grinding of the mineral. The name comes from the Greek. gypsos, which in ancient times meant both gypsum itself and chalk. A dense, snow-white, cream, or pink, fine-grained variety of gypsum is known as alabaster.

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STRUCTURE

The chemical composition is Ca × 2H 2 O. The syngony is monoclinic. The crystal structure is layered; two sheets of 2- anionic groups closely associated with Ca 2+ ions form double layers oriented along the (010) plane. Molecules of H 2 O occupy places between these double layers. This easily explains the very perfect cleavage characteristic of gypsum. Each calcium ion is surrounded by six oxygen ions belonging to the SO 4 groups and two water molecules. Each water molecule binds a Ca ion to one oxygen ion in the same double layer and to another oxygen ion in the adjacent layer.

PROPERTIES

The color is very different, but usually white, gray, yellow, pink, etc. Pure transparent crystals are colorless. Impurities can be dyed in different colors. The dash color is white. The luster of the crystals is glassy, sometimes with a mother-of-pearl tint due to microcracks of perfect cleavage; selenite is silky. Hardness 2 (standard on the Mohs scale). Cleavage is very perfect in one direction. Thin crystals and cleavage plates are flexible. Density 2.31 - 2.33 g / cm 3.
It has significant solubility in water. A remarkable feature of gypsum is the fact that its solubility reaches a maximum at 37-38°C with increasing temperature, and then drops rather quickly. The greatest decrease in solubility is established at temperatures above 107 ° due to the formation of a "hemihydrate" - CaSO 4 × 1 / 2H 2 O.
At 107°C, it partially loses water, turning into a white powder of alabaster, (2CaSO 4 × H 2 O), which is noticeably soluble in water. Due to the smaller number of hydrate molecules, alabaster does not shrink during polymerization (increases in volume by approx. 1%). Under p. tr. loses water, splits and fuses into white enamel. On charcoal in a reducing flame it gives CaS. It dissolves much better in water acidified with H 2 SO 4 than in pure water. However, at a concentration of H 2 SO 4 over 75 g/l. solubility drops sharply. Very slightly soluble in HCl.

MORPHOLOGY

Due to the predominant development of (010) faces, crystals have a tabular, rarely columnar, or prismatic appearance. Of the prisms, (110) and (111) are the most common, sometimes (120) and others. Faces (110) and (010) often have vertical shading. Intergrowth twins are frequent and are of two types: 1) Gallic according to (100) and 2) Parisian according to (101). It is not always easy to tell them apart. Both of them resemble a dovetail. Gallic twins are characterized by the fact that the edges of the prism m (110) are parallel to the twin plane, and the edges of the prism l (111) form a reentrant angle, while in the Parisian twins the edges of the prism Ι (111) are parallel to the twin seam.
It occurs in the form of colorless or white crystals and their intergrowths, sometimes colored by inclusions and impurities captured by them during growth in brown, blue, yellow or red tones. Intergrowths in the form of a “rose” and twins are characteristic - the so-called. " dovetails"). It forms veinlets of a parallel fibrous structure (selenite) in clayey sedimentary rocks, as well as dense continuous fine-grained aggregates resembling marble (alabaster). Sometimes in the form of earthy aggregates and cryptocrystalline masses. It also forms the cement of sandstones.
Common are pseudomorphs after gypsum of calcite, aragonite, malachite, quartz, etc., as well as pseudomorphs of gypsum after other minerals.

ORIGIN

A widely distributed mineral, it is formed in natural conditions in various ways. Sedimentary origin (typical marine chemogenic sediment), low-temperature hydrothermal, found in karst caves and solfatars. Precipitated from sulphate-rich aqueous solutions during the drying of sea lagoons, salt lakes. Forms layers, layers and lenses among sedimentary rocks, often in association with anhydrite, halite, celestite, native sulfur, sometimes with bitumen and oil. In significant masses, it is deposited by sedimentation in lacustrine and marine salt-bearing dying basins. At the same time, gypsum, along with NaCl, can be released only in initial stages evaporation when the concentration of other dissolved salts is not yet high. Upon reaching a certain value of the concentration of salts, in particular NaCl and especially MgCl 2, anhydrite will crystallize instead of gypsum and then other, more soluble salts, i.e. the gypsum in these basins must belong to the earlier chemical precipitation. Indeed, in many salt deposits, layers of gypsum (as well as anhydrite), interbedded with layers of rock salt, are located in lower parts deposits and in some cases are underlain only by chemically precipitated limestones.

In Russia, thick gypsum-bearing strata of Permian age are distributed in the Western Urals, in Bashkiria and Tatarstan, in Arkhangelsk, Vologda, Gorky and other regions. Numerous deposits of the Upper Jurassic age are established in the North. Caucasus, Dagestan. Remarkable collection specimens with gypsum crystals are known from the Gaurdak deposit (Turkmenistan) and other deposits. Central Asia(in Tajikistan and Uzbekistan), in the Middle Volga region, in the Jurassic clays of the Kaluga region. In the thermal caves of Naica Mine, (Mexico), druze of gypsum crystals of unique size up to 11 m long were found.

APPLICATION

Today, the mineral "gypsum" is the main raw material for the production of α-gypsum and β-gypsum. β-gypsum (CaSO 4 0.5H 2 O) is a powdered binder material obtained by heat treatment of natural two-water gypsum CaSO 4 2H 2 O at a temperature of 150-180 degrees in apparatus communicating with the atmosphere. The product of grinding β-modification gypsum into a fine powder is called building gypsum or alabaster, with finer grinding, molding gypsum is obtained or, when raw materials of increased purity are used, medical gypsum.

During low-temperature (95-100 °C) heat treatment in hermetically sealed apparatus, α-modification gypsum is formed, the grinding product of which is called high-strength gypsum.

In a mixture with water, α and β-gypsum hardens, turning back into dihydrate gypsum, with heat release and a slight increase in volume (approximately 1%), however, such a secondary gypsum stone already has a uniform fine-crystalline structure, the color of various shades of white (depending on raw materials), opaque and microporous. These properties of gypsum are used in various fields of human activity.

Gypsum (English Gypsum) - CaSO 4 * 2H 2 O

CLASSIFICATION

Strunz (8th edition)	6/C.22-20
Nickel-Strunz (10th edition)	7.CD.40
Dana (7th edition)	29.6.3.1
Dana (8th edition)	29.6.3.1
Hey's CIM Ref.	25.4.3

PHYSICAL PROPERTIES

Mineral color	colorless turning into white, often colored by minerals-impurities in yellow, pink, red, brown, etc.; sometimes there is a sectorial-zonal color or distribution of inclusions over growth zones inside the crystals; colorless in internal reflexes and through.
Dash color	white
Transparency	transparent, translucent, opaque
Shine	glassy, close to glassy, silky, pearlescent, dull
Cleavage	very perfect, easily obtained from (010), almost mica-like in some samples; according to (100) clear, turning into conchoidal fracture; by (011), gives a splintery fracture (001)
Hardness (Mohs scale)	2
kink	smooth, conchoidal
Strength	flexible
Density (measured)	2.312 - 2.322 g / cm 3
Radioactivity (GRapi)	0

In life, none of us is immune from the danger of fractures of various limbs. In such cases, it is very important to correctly apply a plaster cast on time. Ordinary gypsum, which has been used for over a century, gives the patient discomfort and discomfort, so scientists have developed an innovative product in the medical market - plastic gypsum, which does not have a number of disadvantages inherent in a conventional bandage. From this article you will learn what positive and negative characteristics plastic gypsum has, its main types and methods of application in practice.

Turbocast - polymer bandage

Note! This device is used only on the advice of a physician (orthopedist, traumatologist or surgeon) who must examine the injured limb and, based on the results of the examination, decide to apply or refrain from using such an orthopedic device.

Disadvantages of plastic plaster

This innovative product has a number of negative points, so before using it in practice, you should study these negative points. The disadvantages include the following:

It can not be cut in a place where tissue compression occurs.
High price for material, replacement and overlay.
At long-term operation muscle atrophy occurs.

Benefits of the new technology

But, the listed disadvantages of the device are more than overlapped nearby positive characteristics. Among which are the following:

The ability to use polymer plaster on the arm, leg or other injured limb.
Very light, which will not create a feeling of discomfort to the patient.
Moisture resistant, which makes it possible to take water procedures.
Hypoallergenic ( any will do even the most sensitive skin).
Possibility of giving various forms.
Tightly fixes and fits over the entire area of application.
Ease of wearing.
Ventilated, which allows air to flow freely in places of imposition.

3D plaster made on the printer

Plastic plaster on the leg

This material has several types, each of which is superimposed in a special way. Some polymer plasters are applied using a special material made in the form of a stocking, which is used as a layer between the plaster and the skin. Other polymer bandages do not require application during installation. additional materials, but the overlay process is accompanied by certain temperature procedures that are performed by a medical specialist.

The temperature procedure is the heating of the polymer to 60-65 degrees (becomes elastic) and subsequent cooling to 35-40 degrees, when it can be applied and fixed in a certain position.

Withdrawal plastic plaster

The procedure is simple, but when performing it, you need to take into account many factors and have certain knowledge, so only an experienced doctor can handle it.

Bandage removal is also performed medical worker, since it is not possible to perform this procedure at home. To do this, use a special saw, which cuts the polymer material. Removal, like installation, is not accompanied by pain.

Plastic plaster on hand

This product is a polymer bandage that is applied to the affected area of the hand. The difference between this orthopedic device and ordinary gypsum is that the polymer material is very light and easy to use. With plastic gypsum, the patient can lead a normal life without experiencing discomfort and pain in the places of application.

Polymer plaster can be used not only for an injury to the hand, but also if received or a finger. A plastic bandage securely fixes the limb and prevents the loss of its flexibility, which is a favorable factor influencing the process of bone fusion.

Gypsum Polyfix on the arm

Types of plastic plaster

This innovative material has several types, each of which has its own characteristics and features. There are three main types of polymer gypsum: turbocast, primcast and softcast. They differ from each other in the materials from which they are made, and also have their positive and negative points use.

Softcast material

This polymer is used not only for fractures, but also for sprains of the limbs, due to its elasticity and flexibility. Softcast is a polyurethane resin-impregnated fiberglass fabric that allows air to circulate unhindered through its structure. This material does not allow moisture to pass through, which makes it waterproof.

Primcast based on polyester fiber

This type is considered one of the best, among other materials of plastic gypsum. It is based on unique material- polyester fiber, which is hypoallergenic, and also has the following number of positive characteristics:

Primcast in the package

Relatively cheap, considering the prices of similar materials.
Environmentally friendly (no toxicity).
Gives you the opportunity to quickly remove puffiness, as it has a positive effect on the "muscle pump".
high throughput air.
Adjustable level of rigidity, which is determined by the attending physician.

Advantages of a turbocast

Plastic gypsum made from this material is the newest word in the treatment of various types of fractures and bone injuries. It distinguishes high price, since the manufacturing process uses an innovative material - polycapralactone. This material is different high level ease of use, as well as absolute safety during operation.

It is used for all types of fractures of the limbs.

Gypsum plastic Turbocast

In addition to the above characteristics, there are a number of other good points turbocast, namely:

Absolute material safety.
Applicable to all age categories of people.
Mobility that allows you to independently remove and put on a fixative (gypsum).
Possibility of modeling.
It is possible to produce an x-ray of the bone without removing the plastic plaster.
Breathable (breathable).
Waterproof.

Along with significant advantages, the material has some disadvantages, namely:

A very complex process of imposition and fixation.
The high cost of the polymer (compared to other types of plastic gypsum).

The cost of plastic gypsum and where to buy

Note! These orthopedic products are sold only in specialized orthopedic stores or pharmacies.

Do not purchase polymers from hand or from little-known manufacturers and companies.

Below is the price segment for products, as well as online stores where you can buy plastic gypsum.

Turbokas - average price in Russia, is 9-15 thousand rubles.
Softcast - more cheap option, the price of which varies from 2 to 4 thousand rubles.
Primcast is a budget option, with price segment 1-2 thousand rubles.

Gypsum Polifix on the finger

List of orthopedic centers and shops selling these polymers:

Orthopedic salon "Ortogid", located at www.ortogid.ru.
Dobrota medical store located at www.dobrota.ru.
Network of medical stores "Gradusnik", located at www.gradusnik.pro.

Conclusion

After limb fractures the best option quick recovery will be the use of plastic retainers, which have a number of advantages over conventional gypsum made from natural minerals. Due to the absence of discomfort and problems in the operation of the device, polymer plaster has earned respect and positive feedback from both patients and physicians working with this innovative material.

Gypsum- a natural mineral from the class of sulfates. Of all natural sulfates in the construction industry, highest value. In nature, it is in the form of a dihydrate - dihydrate calcium sulfate CaSO 4. 2H 2 O and in an anhydrous state - anhydrite CaSO4.

Basically, gypsum is used mainly as a raw material for the production of low- and high-firing gypsum binders and as an additive introduced when grinding Portland cement clinker and its varieties in order to control the setting time.

Another direction of using natural gypsum is the manufacture of wall and partition products, which is due to its low thermal conductivity: at 30 ° C 0.28-0.34 W / (m.K).

Natural gypsum dihydrate is a rock of sedimentary origin, composed mainly of large and small CaSO 4 crystals. 2H 2 O. Intergrowths of gypsum crystals can form plaster roses. Dense formations of gypsum are called gypsum stone.

Structural differences

According to the appearance and structure of the rock, there are:

crystal transparent plaster;
poikilitic or sandy gypsum - crystals overflowing with sand.
Poikilit(eng. Poikilite) - a crystal or grain that contains numerous inclusions of other minerals that were captured during the growth of the individual.
gypsum spar- a lamellar mineral with flat transparent crystals of a layered structure, individuals of rather large size, transparent (Maryin's eye);
selenite- parallel-fibrous gypsum, yellowish color with a silky sheen
granular gypsum;
alabaster

There are crystalline, fibrous, granular and sandy varieties of gypsum.

Under difference imply a set of mineral individuals of one mineral type, differing in morphological features. For example, the differences of gypsum: "Maryino glass" - lamellar gypsum, selenite - fibrous gypsum.

Gypsum forms continuous marble-like masses, veined accumulations, as well as single crystals and druses. The appearance of its crystals is usually lamellar, columnar and acicular.

Physical properties of gypsum

Crystal lattice of dihydrate gypsum and anhydrite

In the crystal lattice of gypsum dihydrate, each calcium atom is surrounded by six complex groups, consisting of four tetrahedra and two water molecules. The structure of the crystal lattice of this compound is layered. The layers are formed, on the one hand, by Ca 2 + ions and SO 4 -2 groups, and on the other hand, by water molecules. Each water molecule is associated both with Ca 2+ ions and with the nearest sulfate tetrahedron. Inside the layer containing Ca 2 + and SO 4 -2 ions, there are relatively strong (ionic) bonds, while in the direction to the layers containing water molecules, the bond of the layers is much weaker. Therefore, during heat treatment, gypsum dihydrate easily loses water (dehydration process). In practice, this process can be carried out to varying degrees of completion and, depending on this, gypsum binders of various modifications with different properties can be obtained.

In the crystal lattice of anhydrite, sulfur ions are located at the centers of tetrahedral oxygen groups, and each calcium ion is surrounded by eight ions. For the most part anhydrite forms solid masses, but there are cubic, short-columnar, and other crystals.

Gypsum heating

Under the blowpipe, the gypsum loses water, splits and fuses into white enamel. Three effects are observed on the heating curves of gypsum:

at 80-90°C, a certain amount of H 2 0 is released;
at 140°C, gypsum passes into a hemihydrate;
at a temperature of 140-220°C there is a complete release of water;
at a temperature of 400°C, the gypsum is completely fired.

Solubility of gypsum

Gypsum has an appreciable solubility in water (about 2 g/l at 20°C). A remarkable feature of gypsum is that its solubility reaches a maximum at 37-38 °C with increasing temperature, and then drops rather quickly.

The greatest decrease in solubility is established at temperatures above 107 ° C due to the formation of "hemihydrate" - CaSO 4 . 0.5H 2 O. The solubility of gypsum increases in the presence of certain electrolytes (eg NaCl, (NH 4) 2 SO 4 and mineral acids).

Gypsum crystallizes from solution in the form of characteristic needle-shaped crystals, white or colored with impurities.

Gypsum from the Greek - plaster, is easily determined by the following properties:

low hardness;
abundant sublimation of water in a closed tube;
in the flame of an alcohol lamp it turns white (cloudy) and crumbles into powder, melts into white enamel, which gives an alkaline reaction;
relatively poorly soluble in water and acids.

Dissolution of anhydrite is a direct interaction of water and calcium sulfate, saturation occurs when the energy of the hydrated ion becomes equal to the energy of the ion in the lattice. Typically, such dissolution is accompanied by a small heat release (not always and not for all salts). Temperature is the main factor influencing this.

The process of salt dissolution also depends on the properties of the solvent (water), its salinity, composition and pH environment. Thus, the solubility of gypsum increases with an increase in the content of sodium and magnesium chloride salts in water. In distilled water, the solubility of gypsum is 2 g/l, and in highly concentrated solutions of NaCl (100 g/l) or MgCl (200 g/l), the solubility of gypsum increases to 6.5 and 10 g/l, respectively.

Gypsum dissolves well in alkalis and hydrochloric acid. With an increase in the concentration of the alkali solution from 0.1 N. up to 1 n. the solubility of gypsum increases sharply. Thus, depending on the mineralization and composition of the solvent, the dissolution rate of gypsum can vary over a wide range, which must be taken into account when leaching it from the rock.

CaSO 4 + NaCl \u003d NaSO 4 + CaCl 2

CaSO 4 + MgCl \u003d MgSO 4 + CaCl 2

Gypsum variety

Selenite

Selenite is a fibrous difference of gypsum, a translucent mineral, stronger than alabaster. Soft, hardness 2 on the Mohs scale (easily scratched with a fingernail). As inclusions, it may contain clay, sand, rarely - hematite, sulfur, organic impurities.

Has a silky sheen. After polishing, thanks to the parallel fibers, it has a beautiful iridescent optical effect, similar to the effect of a cat's eye.

The color scheme is represented by pink, blue, yellow and reddish-pearl shades. You can also find crystal white selenite.

It is used as an ornamental stone for the manufacture of jewelry, figurines, carved art and household items. Easy to sand sandpaper and well polished. Products made of selenite are easily rubbed and lose their polish due to their low hardness and require re-treatment after use.

Alabaster

The name "alabastrites" comes from the name of the city of Alabaster in Egypt, where the stone was mined. Alabaster was highly prized and was used to make small containers for perfumes and vases for ointments. Cut into thin sheets, alabaster is quite transparent, so it was used to "glaze" windows.

Today, alabaster is the main raw material for the production of gypsum - a powdered binder obtained by heat treatment of natural two-water gypsum CaSO 4 . 2H 2 O at temperatures of 100°C and above.

Let me remind you that alabaster- the purest fine-grained gypsum, resembling marble in appearance, white or light-colored.

Anhydrite

Anhydrite (from other Greek "devoid of water") - anhydrous calcium sulfate. Anhydrite can be white, bluish, grayish, rarely reddish.

When water is added, it increases in volume by about 30% and gradually turns into gypsum dihydrate.

Anhydrite deposits are formed in sedimentary strata mainly as a result of dehydration of gypsum deposits.

Anhydrite is sometimes used as a cheap decorative and ornamental stone, which is intermediate in hardness between jasper, jade and agate, on the one hand, and soft selenite and calcite, on the other.

Today it is used for the production of non-fired and high-fired gypsum binders, as well as an additive for cement production.

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MINISTRY OF EDUCATION AND SCIENCE OF RUSSIA

federal state budgetary educational institution higher professional education

"Russian State University for the Humanities"

Branch in Domodedovo

Department of Mathematical and Natural Sciences

Control work on the discipline:

"Materials Science"

Topic: "Gypsum, its properties, types, brands"

Performed:

4th year student

Groups EZ-4(5.5)

Gakh Elena Vladimirovna

Checked:

Basmanov M.S.

Domodedovo - 2013

Bibliography

1. History of gypsum

Gypsum - natural stone, which was formed as a result of the evaporation of the ancient ocean 110 - 200 million years ago. In the bowels of the earth, gypsum is present in the form of a stone - rocks of sedimentary origin of several varieties. It can be dense in appearance, with a fine-grained structure, sugar-like in a fracture or coarse-grained, with randomly arranged crystals, consist of whiskers with a silky sheen, or be lamellar, with transparent crystals of a layered structure. The color of the rock - white, yellowish, light gray - depends on the presence or absence of various impurities in the rock.

This stone is one of the oldest building materials. His White color, the ability to harden when combined with water, the ability to give the hardening composition any shape has long been used by builders and sculptors. For them, it is the main working material. Due to the ability to quickly acquire strength and the desired shape, due to the high degree of environmental friendliness of the material itself, the role of gypsum in medicine is also great. Known in the past as "alabaster", it was widely used throughout the world in the production of repair and construction work - for interior decoration rooms, interior decorations in the form of stucco on ceilings and walls.

Decorating with stucco has been known since time immemorial. Even in ancient Egypt, in addition to stone carving, decor items made of natural gypsum and alabaster were used, which, by the way, have come down to us in an amazing state. Stucco decoration reached its heyday in antiquity. From excavations, we know magnificent examples of architectural decorations that once created the appearance and interiors of the ancient buildings of Greece and Rome. Since then, throughout the history of art, pictorial ornaments, borders and cornices, columns and pilasters, rosettes and consoles have been so popular - elements that at all times gave any architectural creation a grand and respectable look. Depending on the prevailing style and fashion for finishing materials, it changed appearance decorative reliefs. Carved in marble or cast in plaster, carved in wood and covered with bronze, they were invariably present in the interior of a rich house, adorned the facades of private mansions, "shaped the face", "brought in the spirit" and "created an atmosphere"

The traditions laid down by antiquity were carefully inherited from epoch to epoch, improved and acquired new characteristic features. So, stucco molding served as a worthy decoration of the Renaissance interior and became not just an integral part, but a kind of calling card baroque and rococo furnishings. She managed to achieve another take-off and perfection in the era of classicism. Art Nouveau, which reigned so briefly, also introduced its characteristic features into the history of artistic stucco, giving it capricious elegance, dynamics and asymmetry of the pictorial range.

2. Properties and disadvantages of gypsum

This material has a number of advantages and disadvantages. The advantages of gypsum include a small volumetric mass, fire resistance, good sound insulation. In addition, gypsum is a safe material to use, that is, an environmentally friendly product.

Gypsum has a unique property - when heated, chemically bound water is released from the crystal lattice, forming semi-aqueous gypsum. Such gypsum can be easily powdered. Conversely, when water is added, the mineral binds it in its crystal lattice, restoring its original strength to the gypsum. He creates comfortable environment habitat due to the ability to absorb excess moisture from the air already in trade items and, as the humidity decreases, give it back.

Promotes the fusion of limbs, healing sprains, dislocations and other injuries, curing spinal tuberculosis (gypsum bed), osteomyelitis (fixing the affected organ). Gypsum powder eliminates excessive sweating, gruel from the powder of this mineral, water and vegetable oil is a wonderful toning mask.

The disadvantages of gypsum include low water resistance, low strength and creep under load, especially under conditions high humidity. Gypsum has a relatively short shelf life. It is estimated that already after three months of storage, gypsum loses its strength by about 25-50%. But all these shortcomings can be dealt with by applying certain methods.

So, for example, to increase the water resistance of a gypsum trade item, it is coated with special waterproof paints and pastes, and gypsum trade items are strengthened by impregnation for a day with a solution of 5% ammonium borate heated to 30 ° C.

3. Types of gypsum and its application

Gypsum is one of the most ancient building materials. Its white color, the ability to harden when combined with water, the ability to give the hardening composition any shape has long been used by builders and sculptors. For them, it is the main working material.

Currently, this material is widely used both in raw and fired form.

Raw gypsum is used as an additive to cement to reduce the setting rate, for the production of plaster, and also for the production of fertilizers (gypsum is used to eliminate the alkalinity of the soil).

When firing natural gypsum, alabaster is obtained. Such fired gypsum is widely used for the manufacture of stucco moldings, in medicine, in the paper and cement industries, for the manufacture of drywall, as an ornamental and facing stone, in the production of paints, glazes, and enamels.

It is also widely known to all of us, the so-called medical plaster, which is more often used:

In dentistry, to obtain an impression, a jaw model;

As a molding material;

When soldering;

For fixing models in the occluder (articulator) and cuvettes.

Gypsum for dental practice is obtained by firing natural gypsum. In this case, calcium sulfate dihydrate loses part of the water of crystallization and turns into hemihydrate (hemihydrate) calcium sulfate.

There is also a plaster cast, which is widely used for treatment in traumatology, orthopedics and surgery. This bandage is well modeled, provides reliable fixation, fits snugly and evenly to the body, quickly hardens, is easy to remove and can be applied in any conditions.

4. Brands of gypsum by manufacturers

Orthopedic plaster:

1) Soft, used for taking impressions (occlusal impressions).

2) Conventional, used for applying plaster casts in general surgery (“medical plaster”), for example, Galiplaster (Galenika, Yugoslavia), which includes calcium sulfate hemihydrate.

3) Solid, used for the manufacture of diagnostic and working models of the jaws in the technology of removable dentures, for example, Plaston-L (JC, Japan), Gypsogal (Galenika, Yugoslavia), which includes calcium sulfate hemihydrate .

4) Superhard, used to obtain collapsible models of jaws, for example, Fujikor - EP (JC, Japan), Haligranite (Galenika, Yugoslavia), which includes calcium sulfate hemihydrate.

5) Extra hard, with the addition of synthetic components. This type of gypsum has increased surface strength. Mixing requires a high precision of the ratio of powder and water.

Building plaster:

Gypsum G6 BIII molding

Gypsum G5 B II construction

Gypsum G5 BIII molding

Gypsum G7-G6 AI building

Gypsum G5 BII construction

Gypsum G5 BIII fine grinding.

5. Competitive building materials

St. material	strength	fragility	hardness	Cost (bag) rub.

gypsum building medical

Bibliography

1. Elizarov Yu.D., Shepelev A.F. Materials science for economists. Textbook. - Rostov-on-Don: Phoenix, 2006

2. Arzamasov B.N., Makarova V.I., Mukhin G.G. Materials Science: Textbook. - 3rd ed. M.: Izd - in MSTU im. N.E. Bauman, 2004, 648s.

3. Karpman, V.M. Matyunin M.: Higher School, 2009, 638s.

4. Kolachev B.A., Livanov V.A., Elagin V.I. metallurgy and heat treatment non-ferrous metals and alloys M.: MISIS Publishing House, 2006, 416s.

5. Bartashevich A.A. Materials Science. - Rostov n / a: Phoenix, 2008.

6. Zaplatin V.N. Reference manual for materials science. Proc. allowance for HPE. - M.: Academy, 2007.

7. Materials Science: Textbook for Universities. / Ed. Arzamasova B.N. - M.: MSTU im. Bauman, 2008. 3rd ed.

8. Materials Science: Textbook for open source software. / Adaskin A.M. and others. Ed. Solomentseva Yu.M. - M.: Higher. school, 2006.

9. Bartashevich A.A. Materials Science. - Rostov n / a: Phoenix, 2008.

10. Fundamentals of materials science (metalworking) Zaplatin V.N. - M.: Academy, 2008.

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