Varieties of glass and glass products in construction. Glass: what is it, types, production technology, properties, purpose
Glass types
Type of glass: Window, Tableware, Mirror, Perfume, Bottle, Semi-crystal, Chemical-laboratory, Heat-resistant type, Opal, Thermometric, Electrovacuum, Glass fiber.
In a detailed study of glass, depending on the technical conditions, the following physical and chemical properties are studied: viscosity, surface tension, internal stresses, softening temperature, specific gravity, compressive strength, rupture and bending, hardness, modulus of elasticity, gas permeability, thermal expansion, heat capacity, thermal conductivity, electrical conductivity, dielectric loss, refractive index, spectral characteristics in the visible and invisible parts of the spectrum, chemical resistance, crystallization ability and others. The tensile strength depends on the thickness of the glass and on its heat treatment. Transparent quartz glass has the highest thermal conductivity.
Characteristics of the main types of glass
OPTICAL GLASS -- clear glass any chemical composition with a high degree of uniformity. Contain 46.4% PbO, 47.0% Si0 and other oxides; crowns - 72% SiO, alkali and other oxides.
Optical glass is used for the manufacture of lenses, prisms, cuvettes, etc. Glass for optical instruments was already manufactured in the 18th century, but the actual production of optical glass dates back to the beginning of the 19th century, when the Swiss scientist P. Guinan invented a method of mechanically stirring the glass mass during cooking and cooling - by a circular motion of a clay rod vertically immersed in glass. This technique, which has been preserved to this day, made it possible to obtain glass of a high degree of homogeneity.
The production of optical glass has been further developed by joint work the German scientists E. Abbe and F. O. Schott, as a result of which in 1886 the well-known glass factory of the Schott partnership arose in Jena (Germany), which for the first time produced a huge variety of modern optical glasses.
Until 1914, the production of optical glass existed only in England, France and Germany. In Russia, the beginning of the production of optical glass dates back to 1916. It reached great development only after the Great October Socialist Revolution thanks to the work of Soviet scientists D.S. Rozhdestvensky, I.V. Grebenshchikov, G.Yu. Zhukovsky, N.N. Kachalova and others. The main requirement for optical glass is a high degree of uniformity. The lack of uniformity causes the light rays to deviate from their correct path, making the glass unsuitable for its intended purpose.
The homogeneity of optical glass is disturbed by chemical and physical causes. Chemical heterogeneity is due to local changes in the chemical composition and is eliminated by stirring the optical glass during the melting process. Physical inhomogeneity is caused by stresses that occur during the cooling of optical glass and is eliminated by careful annealing. Optical glass must have certain optical properties--accurate refractive indices for rays of different wavelengths. A large assortment of optical glass with different refractive indices and average dispersion is of great importance in the calculation and design of optical systems to reduce their defects, in particular, to eliminate the harmful effects of the secondary spectrum and improve image quality.
The optical properties of glass depend on its chemical composition. Various combinations of oxides make it possible to obtain glass with the required values of optical constants. Some grades of optical glass, for example, do not contain silica (the main constituent of any glass), others contain commonly used oxidizers, but in extremely large quantities.
The transparency of the optical glass must be high, on the order of 90-97% per 100 mm of the beam path in the glass. Optical glass must be chemically resistant to the action of a humid atmosphere and to the action of weak acids, which characterizes their “spotting”, i.e., sensitivity to the touch of hands.
Optical glass uses the same raw materials as other types of glass. However, the requirements for the purity of raw materials are very high. Particularly harmful impurities are iron and chromium compounds, which color glass and increase its light absorption. The melting of optical glass is carried out in one- and two-pot furnaces.
The most important operation in the production of optical glass is the stirring of the glass during the melting process and especially during the cooling process. Three methods are used to cut optical glass:
- 1) cooling the glass together with the pot, followed by breaking into pieces and forming these pieces in a heated state;
- 2) casting glass melt into an iron mold;
- 3) rolling into a sheet of glass mass cast on the table.
Optical glasses are produced by glass factories in the form of rectangular pieces of various sizes "tiles" and in the form of blanks - "pressing" (lenses, prisms). Optical glasses also include specially colored colored glasses used for the manufacture of precise light filters, which are often used in optical instruments in the form of plane-parallel plates and serve to change the spectral composition of the light passing through them. These colored glasses are made in optical glass factories using the same methods as optical glass.
BUILDING GLASS - glass products used in construction. Building glass is used for glazing skylights, for making transparent and translucent partitions, for cladding and finishing walls, stairs and other parts of buildings. Building glass also includes heat and sound insulating glass materials (foam glass and glass wool), glass pipes for concealed electrical wiring, plumbing, sewerage and other purposes, architectural details, elements of glass-reinforced concrete floors, etc.
Most of the range of building glass is used for glazing light openings: sheet window glass, mirror, corrugated, reinforced, patterned, two-layer, hollow blocks, etc. The same range of glass can be used for the construction of transparent and translucent partitions.
Sheet window glass, most widely used in construction, is produced from molten glass mass, mainly by vertical or horizontal continuous drawing of a tape, from which, as it cools and solidifies, sheets of the required dimensions are cut from one end. A significant disadvantage of sheet window glass is the presence of some waviness that distorts objects viewed through it (especially at an acute angle).
Mirror glass is processed by grinding and polishing on both sides, so that it has minimal optical distortion.
The modern, most common method for the production of mirror glass consists in horizontal continuous rolling of glass mass between two shafts, annealing the molded strip in a tunnel furnace, grinding and polishing on mechanized and automated conveyor installations. Mirror glass is made with a thickness of 4 mm and more (in special cases - up to 40 mm), high-quality materials are used for cooking it, therefore it also has a higher light transmission than ordinary window glass; it is used mainly for glazing windows and doors in public buildings, shop windows and for the manufacture of mirrors; mechanical properties differ little from the mechanical properties of window glass. Rolled patterned glass has a patterned surface obtained by rolling between two rolls, one of which is corrugated; both colorless and colored are produced; used in cases where diffused light is required. Patterned glass with a frosted or "frosty" pattern is used for internal partitions, door panels and glazing of staircases; It is made by processing the surface of window or mirror glass.
A matte pattern is obtained by treating the surface with a jet of sand under the template. A pattern resembling a frosty pattern on glass is obtained by applying a layer of animal glue to the surface, which, during the drying process, comes off along with the upper layers of glass. Reinforced glass contains a wire mesh in its thickness; it is more durable than usual; when broken by blows or cracking during a fire, its fragments crumble, being bound by reinforcement; Therefore, reinforced glass is used for glazing industrial and industrial lanterns. public buildings, elevator cabins, stairwells, openings of fire walls.
It is produced by the method of continuous rolling between rolls with wire mesh rolled up from a separate drum. Corrugated reinforced glass, shaped like corrugated asbestos-cement sheets, is used for partitions, skylights, glass galleries and passages.
Double (package) glasses with an air or light-diffusing layer (for example, made of glass fiber) have good thermal insulation properties; are made by gluing 2 panes of glass with a spacer frame. The thickness of double panes with an air gap is 12-15 mm. Hollow glass blocks are made by pressing and subsequent welding of two glass half-boxes; are used to fill light openings, mainly in industrial buildings; provide good illumination of workplaces and have high thermal insulation properties.
Blocks are laid in openings using mortar in the form of panels tied with metal bindings. Facing glass (marblit) represents opaque color sheet glass. It is produced by periodic rolling of glass mass on a casting table, followed by annealing in tunnel furnaces. It is used for finishing facades and interiors of residential and public buildings. Colored metallized glass also belongs to facing glass.
QUARTZ GLASS -- contains at least 99% SiO- (quartz). Quartz glass is smelted at temperatures above 1700°C from the purest varieties of crystalline quartz, rock crystal, vein quartz, or pure quartz sands. Quartz glass transmits ultraviolet rays, has a very high melting point, thanks to a small coefficient of expansion withstands sudden changes in temperature, resistant to water and acids. Quartz glass is used for the manufacture of laboratory glassware, crucibles, optical instruments, insulating materials, mercury lamps ("mountain sun") used in medicine, etc.
ORGANIC GLASS (plexiglass) is a transparent colorless plastic mass formed during the polymerization of methacrylic acid methyl ester. Easily machinable. It is used as sheet glass in aircraft and mechanical engineering, for the manufacture of household products, protective equipment in laboratories, etc.
SOLUBLE GLASS - a mixture of sodium and potassium silicates (or only sodium), aqueous solutions of which are called liquid glass. Soluble glass is used for the manufacture of acid-resistant cements and concretes, for the impregnation of fabrics, the manufacture of fire-retardant paints, silica gel, for strengthening weak soils, stationery glue, etc.
GLASS CHEMICAL-LABORATORY - the glass possessing high chemical and thermal firmness. To improve these properties, zinc and boron oxides are introduced into the glass composition.
GLASS FIBER - an artificial fiber of a strictly cylindrical shape with a smooth surface, obtained by stretching or dismembering molten glass. It is widely used in the chemical industry for filtering hot acidic and alkaline solutions, purifying hot air and gases, making stuffing box packings in acid pumps, reinforcing fiberglass, etc.
Each specific type of glass must perform a very specific function. There are five main functions of glass: thermal insulation in winter; protection against overheating of rooms in summer; soundproofing; security, aesthetic.
To implement these functions, various types of glasses have been developed, we will consider them in more detail.
Energy saving glass
Thermal insulation in winter period is the most important function of glasses for most regions of Russia. As mentioned above, heat loss through glass is made up of heat conduction, convection, and heat radiation. To reduce heat loss from thermal conduction and convection, double glazing (double-glazed windows, see below) is used, but this has only a minor effect, because. the main heat loss occurs due to thermal radiation. To combat this, so-called energy-saving glasses have been developed.
Giving energy-saving properties to glass is associated with the deposition of low-emission optical coatings on its surface, and the glass itself with such a coating is called low-emissivity. These coatings allow the passage of short-wave solar radiation into the room, but prevent long-wave thermal radiation from escaping the room, for example from a heater (therefore, glasses with low-e coatings are also called selective glasses).
The characteristic of energy saving is the emissivity of glass. Under the emissivity of glass (emission) is understood the ability of a glass surface to reflect long-wave thermal radiation, invisible to the human eye, whose wavelength is less than 16,000 nm. The surface emitter (E) determines the emissivity of the glass (for ordinary glass, E is "0.83, and for selective glass it is less than 0.04) and, therefore, the ability to "reflect" heat radiation back into the room.
The reason for the appearance of radiation lies in the movement of free electrons of atoms located on the glass surface, and the density of moving electrons. Not all metals that conduct electricity well have the ability to reflect long-wave thermal radiation.
Therefore, the lower the emitter, the less heat loss. At the same time, glass with an optical coating having an emitter value of E = 0.004 reflects back into the room more than 90% of the thermal energy leaving through the window.
Currently, two types of coatings are used for these purposes: the so-called K-glass (Low-E) - a "hard" coating - and i-glass (Double Low-E) - a "soft" coating.
The first step in the production of energy-saving glass was the production of K-glass. To impart heat-saving properties to float glass directly during manufacture, a chemical reaction at high temperature (pyrolysis method) is created on its surface. thin layer from metal oxides InSnO2, which is transparent and at the same time has electrical conductivity. It is known that electrical conductivity is directly related to the emissivity of the E-surface. Emissivity value plain glass is 0.84, and K-glass is usually about 0.2.
The next significant step in the production of heat-saving glasses was the release of the so-called. i-glass, which in terms of its heat-saving properties is 1.5 times superior to K-glass. The difference between K-glass and i-glass lies in the emissivity, as well as the technology for its production.
I-glass is produced vacuum deposition and is a triple (or more) structure of alternating layers of dielectric silver (BiO, AlN, TiO2, etc.). The application technology requires the use of high-vacuum equipment with a magnetron sputtering system.
The main disadvantage of i-glasses is their reduced abrasive resistance compared to K-glass, which presents some inconvenience during their transportation, but given that such a coating is inside the double-glazed unit, this does not affect its performance properties.
It should also be noted that when working with K-glass and i-glass, cleaning (ie removal) of the coating is required at the point of contact between the distance frame (see the "Insulating glass" section below) and glass. This is necessary to prevent corrosion of the coating along the surface during operation, as well as to increase the adhesion of butyl to glass.
The main field of application of glasses is their use as part of double-glazed windows, the heat-saving properties of which are largely determined by the parameters of the coating on the glass.
Sunglasses
Solar control glass is understood to mean glass that has the ability to reduce the transmission of light and/or solar thermal energy. Sun protection are, for example, colored glass throughout the mass, as well as some types of glass with coatings.
Body-tinted glass is made by adding metal oxides to molten glass. These oxides determine not only the final color of the product (bronze, gray, green or blue), but also determine its light and energy properties.
Tinted glass partially absorbs heat rays, while remaining transparent enough for visible light. The reduction in solar heat penetration is due to the fact that part of the heat that hits the glass is absorbed by the glass itself.
The absorbed heat is then released to the side where the air temperature is lower. The amount of heat that penetrates glass depends on its color and thickness.
According to the mechanism of action, sun glasses can be divided into 2 groups: predominantly reflecting radiation and predominantly absorbing radiation.
Solar-reflective glasses of the first group are sheets of colorless or colored glass, one side of which is covered with a thin transparent layer of metal oxides (applied during production), which prevents the penetration of radiation through the glass. It should be noted that the reflective layers simultaneously absorb some part of the radiation. It is possible to install such glasses both with a coating inside the room and outside. The location of the cover is very important as this is what determines both the shade of the glass and its technical characteristics.
In the manufacture of absorbing glasses, either crystals of metals or metal oxides are applied to the molten glass mass, which have the ability to absorb part of the solar radiation. In parallel with this, the glass heats up and gives off most of the heat they receive to the outside. Part of the heat, however, is transferred to the inside of the room, which is of course an undesirable phenomenon, since it increases the energy demand for cooling the room.
Designs that combine reflective coatings and low emissivity coatings are a new product that has appeared on the market.
Fully reflective surfaces of transparent glasses are obtained by sequentially applying several layers of coating to the surface of the glass. Typically, the number of coating layers is five, of which four are metal oxide layers, and the fifth working layer consists of silver. Silver has the ability to transmit visible light in the same way as ordinary glass. In the case when the wavelength is greater than 0.76 microns, silver almost completely reflects all radiation. In addition, such glasses also have good thermal insulation properties.
laminated glass
Laminated glass (triplex) is an architectural glass consisting of two or more glasses laminated together with a laminating film or a special laminating liquid.
Lamination does not increase the mechanical strength of the glass, however, when broken, the laminated glass does not crumble due to laminated film, i.e. fragments remain attached to it. Laminated glass also provides better soundproofing of rooms, because Laminated glass can effectively reduce the impact of unwanted noise.
Different types of laminating films can provide almost any glass tinting. Laminated glass is used for glazing facades, balconies and windows.
Reinforced glass
Armored glass - sheet glass with a metal mesh, safe and fire resistant, serving as an effective barrier against smoke and hot gases. In a fire, it can crack, but the reinforcement holds it in place, thereby preventing the spread of fire. Glass shards do not fall out even when several breaks are formed, held by reinforcement. Armored glass can be used for glazing factory floors, windows, skylights, elevator shafts and facades.
tempered glass
Tempered glass is glass that has been chemically or thermally treated to increase its resistance to impact and temperature changes compared to ordinary glass. When broken, tempered glass breaks into small, harmless pieces. You should pay attention to the fact that tempered glass is not subject to mechanical processing, therefore, it must be performed before the tempering process.
Almost all types of glass can be tempered, with the exception of reinforced and some types of decorative glass. Tempered glass can be used in the production of insulating glass or laminated glass.
For facades, tempered glass is also used, on which a special paint such as ceramic frit is applied. The sheet treated in this way is used as an opaque cover panel for facade parapets, and can be inserted into a double-glazed window or used independently. A number of companies also offer services for applying various patterns to glass using the silk-screen printing method (on order).
Protective glasses
The classification of protective glasses and the requirements for them are contained in GOST R 51136.
Protective laminated glass is silicate glass plates glued together with polymeric materials in various combinations with organic glass, polycarbonate or reinforcing films. Glass is a multilayer block with protective properties.
Impact-resistant glass is a protective glass that can withstand multiple impacts of a freely falling body with normalized performance.
Penetration-resistant glass is a protective glass that can withstand a certain number of blows with a butt and an ax blade, applied with standardized indicators.
Bullet-resistant glass is protective glass that can withstand the impact of firearms and prevent the through penetration of the damaging element.
PROTECTIVE GLASSES (GOST R 51136)
impact resistant glass
Impact-resistant glass, depending on its characteristics, is divided into protection classes A1, A2 or A3.
Classification of impact resistant glass
Impact-resistant glass, depending on the application temperature, can be of two types:
- used at temperatures above 0 °C;
- used at temperatures below 0 ° C and tested for frost resistance.
Penetration resistant glass
Penetration-resistant glass is divided into protection classes B1, B2 and B3.
Punch-resistant glass classification
| Glass protection class | Hits with a hammer, ax butt | Ax blade strikes | Total number of strokes | ||
| Impact energy, J 15 | Counter impact speed, m/s 0.3 | Impact energy, J 15 |
|||
| B1 | 12,5 | 350 | 11,0 | 300 | 30 to 50 |
| B2 | 12,5 | 350 | 11,0 | 300 | 51 to 70 |
| B3 | 12,5 | 350 | 11,0 | 300 | St. 71 |
Bulletproof glass
Bullet-resistant glass, depending on its resistance when fired from a certain type of weapon, certain ammunition, is divided into protection classes B1, B2, B3, B4, etc.
Bulletproof glass can be of two types: shatterproof and shatterproof.
Shatterproof, that is, when exposed to firearms on back side glass does not form fragments or the formed fragments are not dangerous to the health of a person who is in the immediate vicinity of the protective glass.
Fragmentation, that is, when exposed to a weapon, fragments are formed on the back of the glass.
Classification of glass depending on the means of destruction and the characteristics of the striking element (bullet)
| Protection class | Means of destruction | Name and cartridge index | Bullet characteristic | Firing distance, m | |||
| Core type | Weight, g | Speed, m/s 10 | Caliber, mm | ||||
| IN 1 | Makarov pistol (PM) | Cartridge 57-N-181 | Steel | 5,9 | 315 | 9 | 5 |
| IN 2 | Tokarev pistol (TT) | Cartridges 57-N-132S, 57-N-134S | Same | 5,5 | 420 | 7,62 | 5 |
| B3a | AK-74 assault rifle | Cartridge with bullet 7H6 | Steel non-thermo-strengthened | 3,4 | 880 | 5,45 | 5-10 |
| IN 3 | AK-74 assault rifle | Cartridge 57-N-231 with PS-43 bullet | Same | 3,4 | 715 | 7,62 | 5-10 |
| AK-74 assault rifle | Cartridge with a bullet 7H10 | Steel heat-strengthened | 3,5 | 880 | 5,45 | 5-10 | |
| AT 4 | AKM assault rifle | Cartridge 57-N-231 | Same | 7,9 | 715 | 7,62 | 5-10 |
| B5a | AKM assault rifle | Cartridge with armor-piercing incendiary bullet (B3) | Steel | 7,4 | 745 | 7,62 | 5-10 |
| AT 5 | SVD rifle | cartridge ST-2M | Steel heat-strengthened | 9,6 | 825 | 7,62 | 5-10 |
| AT 6 | SVD rifle | Cartridge with bullet B3-32 | Steel | 10,4 | 820 | 7,62 | 5-10 |
fireproof glass
In many cases, building glazing must be fireproof to comply with building codes that limit the spread of fire in a fire and allow for the safe evacuation of people from a building. In addition to the reinforced glass used for these purposes (discussed above), leading glass manufacturers have also developed special types fireproof glass. For example, laminated glass with transparent, heat-expanding intermediate layers. In the event of a fire, at a temperature of about 120 0C, these layers change their physical characteristics and the glass turns into a rigid and opaque protective structure, allowing the glazing to maintain:
- integrity, i.e. ensure the absence of through cracks or holes through which combustion products or flames penetrate the protected space;
- heat-insulating ability that prevents the transfer of heat to the protected space by radiation.
Electrically heated glass
Electrically heated glass is made on the basis of low-e glass with connection to it electric current. This glass functions as a thermal mirror that transmits light but reflects heat. Thus, when connected to a voltage source, the glass surface heats up, which can be used for a variety of purposes: reducing the circulation of cold air in rooms, increasing the overall temperature (body source), snowmelt, etc. Depending on the application, the range of electric glass is from 50 to 600 W/m2.
Self-cleaning glass
Self-cleaning glass is ordinary glass with a special coating on the outer surface of the glass, which has a double effect. When exposed to daylight glass, its coating reacts to light in two ways. Firstly, it destroys any organic dirt deposits and, secondly, rainwater, flowing down the glass, washes away the destroyed organic dirt.
patterned glass
Patterned glass is sheet glass, one surface of which has a decorative treatment. It may be different colors, drawings, different thickness(4-6mm and have different light transmission. Patterned glass can be tempered and laminated.
Most patterned glass can be used in energy-saving or sound-absorbing double-glazed windows.
Glass decoration
A variety of technologies are used to decorate glass: transparent and matt etching, decoration and painting with transparent and dull thermosetting paints, sandblasting, stained glass and stained glass imitations, beveling and painting, and others.
Painting technology is a heat treatment of already finished sheet glass, which allows you to give it (heating to a certain softening temperature) the required shape, and then, by slow cooling, keep it in the finished product. This technology is used both for the manufacture of glass inserts, and in more complex versions, for semicircular doors of sanitary equipment (showers, bathtubs) and saunas.
Sandblasting is a traditional glass decoration technology based on the mechanical treatment of the glass surface with an air jet containing abrasive particles. The resulting matte pattern can have different grain sizes and processing depths.
Chemical etching and matting. This process is based on the properties of hydrofluoric acid vapors to interact with glass, forming insoluble salts. Depending on the processing mode, etching makes it possible to obtain both a uniformly matte and transparent pattern with different processing depths on places not protected by acid-resistant mastic. This process is very time-consuming and time-consuming, therefore, as a rule, it is used only for decorating expensive highly artistic products.
Beveling is a special processing of glass edges. Beveled inserts are usually used in expensive wooden doors, the most valuable is the processing of the so-called curly facet of beautiful curved surfaces with high accuracy.
The stained glass technology is based on a set of drawings from pieces of glass dyed in mass. The glass used for stained-glass windows is corrugated, rather rough; special sheet colored and smooth tinted, processed by bevelling. Glass is connected into a single whole by a strip of soft metal having a special section.
There are other methods of decorating the glass surface. If it is necessary to obtain a color pattern on glass, as a rule, the silk-screen printing method is used, in which special heat-curing paints are used. As inexpensive decoration methods, glass painting is used, which does not require subsequent heat treatment, as well as decoration with transparent and opaque films that imitate various methods expensive traditional processing (eg stained glass and frosted glass).
Decorative paints for glass allow you to create various surface textures: the effects of "etched" glass, sandblasting, metal texture, etc. The use of negative or positive stencils allows you to get patterns or combinations of them on the glass surface.
Applying water-soluble paints to glass is a simple technological process that allows them to be used in small-scale production. Paints can be applied to both horizontal and vertical surfaces.
Such coatings are resistant to chemical and mechanical influences, moisture resistant; suitable for operation in the open atmosphere of an industrial zone of a temperate climate; further processing of glass (facet, cutting, engraving) does not damage the coating.
Data paint coatings used for painting glass doors and office partitions, furniture systems, etc.
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Glass is an amorphous substance that does not have the properties of a crystalline substance in solid form. It is an inorganic melting product cooled to a solid state without crystallization. Glass is a solidified liquid. Its density is 2500 kg / m³, and the thermal conductivity reaches 0.84 W / m * K. The tensile strength of the glass lies in the range from 30 to 100 MPa. Poisson's ratio is assumed to be 0.25. Modern glasses differ in several ways at once - composition, manufacturing method, appearance and additional properties.
According to the chemical composition, glass differs in soda-lime glass and borosilicate glass. The main components of the first are silicon dioxide, sodium and calcium oxides, and the second contains boron.
According to the manufacturing method, glass can be sheet (sheet glass), drawn (drown glass), rolling (rolled glass), flat polished (polished plate), laminated (laminated glass), tempered (toughed glass), and also thermally polished - float glass (float glass). According to the manufacturing method, energy-saving (low-emission) glass can be hard coated (hard coat glass) - the so-called K-glass or soft coated (soft coated glass) - the so-called E-glass.
In appearance, glass is divided into clear (clear glass), super-clean (extra-clear glass), tinted glass (tinted glass), patterned rolling (figured rolled glass), reflective (reflective glass), mirror (mirror), stained glass (stained glass), reinforced (wired glass) and bent (curved glass), also called curved.
According to additional properties, glass is divided into fire-resistant (flameproof glass), heat-resistant (heat-resisting glass), neutral (neutral glass), solar control (solar control glass), safe (safety glass) and low-emission (low E glass). Fire-resistant glass does not break for some time when heated or in contact with a flame, and heat-resistant glass, due to its low coefficient of thermal expansion, is able to withstand severe thermal shock. Due to the insignificance of these differences, these two types of glasses are often combined in the classification.
Glasses that are different in one or more characteristics according to the classification just given can belong to the same or different types according to their intended purpose (according to the way they are used). There is no strict division in this regard. Comparative characteristics of different types of glass will be discussed in detail below. At the same time, the division of glasses into grades is strict. Brands of glass - symbols of glass, depending on its characteristics and scope. There are eight grades of glass (M0-M7), which are installed depending on its quality in accordance with GOST 111-2001 "Sheet glass. Specifications". The lower the serial number of the brand, the better quality glasses according to optical distortions and permissible defects appearance. Despite the existence of the M0 brand, the very widespread glass of the M1 brand is also considered to be of the highest quality. The quality of glass grades M2 and M3 is considered average. According to GOST 111-2001, for M1 glass, up to four defects per 1 m² are allowed, and the distance between them must be at least 300 mm. Noticeable blotches are typical for M2 glass. If, when viewed through glass at an angle of 45 °, the picture allows iridescent stains and "floats", then this is glass of the M3 brand.
Comparative characteristics of different types of glass
Bor glass - in the literal sense, this is glass produced by a plant in the city of Bor, Nizhny Novgorod Region. Since large volumes of production and high quality made the glasses of the Borsky plant very common and well-known in our country, in a figurative sense, "Borsky glass" is called high-quality sheet glass of the M1 brand. Today the name "borsk glass" has become a household name.
Sheet glass is flat glass, the treated surface of which does not allow optical distortion. Microroughnesses on the surface of polished glass do not exceed 0.01 microns, the light transmission is 87%. Glass, polished thermally, are made in accordance with GOST 7132-78. It is produced in the form of flat sheets with a length of 600 to 1600 mm, a width of 400 to 1300 mm and a thickness of 3, 4, 5 and 6 mm; the dimensions of the sides must be a multiple of 50 mm. Dimensional deviations should not exceed ±2 mm for sheets up to 1 m² and ±3 mm for sheets over 1 m². Polished glass corresponds to the physical and chemical properties common to sheet glass: density 2.58 g/cm³, softening point about 600 °C, heat resistance 60-70 °C. Glass must be chemically resistant. According to GOST, the amount of alkali oxides in terms of sodium oxide, which dissolve during treatment in distilled water at a temperature of 80 ° C for 3 hours, should not exceed 0.15 mg per 100 cm² of the surface of the samples.
Wired glass (wired glass) - sheet glass, inside which, during its production, parallel to the surface plane is laid metal grid. Glass can have a single green cast surface (reinforced cast glass), polished (polished reinforced glass), or translucent with a hexagonal mesh (patterned rolled reinforced glass). Armored glass, together with triplex, belongs to the group of safety glasses, as it does not give falling or rebounding fragments when broken. Due to the presence of the grid, it breaks, but does not disintegrate upon impact, cracks, but also does not disintegrate during a fire, forming an effective barrier to smoke and hot gases. Therefore, it can also be attributed to the group of protective or fire-resistant (fire-prevention) glasses. The metal mesh contributes to a uniform distribution of temperature throughout the glass volume, which reduces thermal stresses. The fire resistance limit of reinforced glass occurs at a temperature of 850-870 ° C compared to 400 ° C for ordinary sheet glass. At the same time, such glass poorly protects against the thermal effects of the flame. The quality of reinforced glass is largely determined by the metal mesh. High-quality reinforced glass should break off along the notch line without cracking. The presence of many "bubbles" in the glass betrays a marriage. The coefficient of total light transmission for glasses reinforced with a welded metal mesh with square cells is 0.6-0.65, and for glasses with a twisted mesh with hexagonal cells 0.68-0.75. One of the surfaces of the reinforced glass may be patterned or corrugated. Colored glasses are stained with metal oxides. The most common colors are golden yellow, green, mauve pink and blue.
Safety glass (safety glass) - tempered glass that does not form fragments with sharp edges when it breaks. As a rule, these are multilayer structures with a thickness of 4 to 120 mm with a light transmission coefficient of at least 85%. Also " safety glasses"They call glasses different in purpose, method of manufacture or other features of glass, which are designed to protect against various external influences. This group includes armored, shatterproof and laminated glass, as well as triplex.
Borosilicate glass (borosilicate glass) - silicate glass containing boron as a characterizing component, in contrast to the widespread soda-lime glass (soda-lime glass), the main components of which are silicon dioxide, sodium and calcium oxides. It is produced by replacing alkaline components in the initial raw material mass with boron oxide. Due to this replacement, the temperature coefficient of linear expansion of the finished glass becomes low, and it acquires the ability to withstand high temperatures. Borosilicate glass is usually safety float glass with a thickness of 5 to 8 mm, with a light transmission coefficient of about 90%. It can be used both independently and in double-glazed windows in combination with other types of glass. After additional heat treatment, borosilicate glass becomes the so-called "special fire-resistant borosilicate glass", capable of containing the spread of fire and smoke for 30, 60 or 120 minutes, even in a single sheet, depending on its thickness. During a fire, the glass remains transparent, its light transmission is the same as that of ordinary glass. On the one hand, this allows people and firefighters leaving the premises to better navigate, and on the other hand, glass transmits not only visible radiation - light, but also thermal radiation, that is, heat from an open fire. Borosilicate glass is not only heat-resistant, but also chemically resistant to various aggressive media. Finished glass is not subject to further processing and therefore is made strictly according to the customer's dimensions or according to ready-made projects.
Armored glass - made, as a rule, on the basis of float glass, special reinforced glass, depending on the degree of protection, capable of withstanding the effects of various small arms. For example, the 1st (minimum) degree guarantees protection against a shot from a PM pistol with a bullet weighing 5.9 g with an initial speed of 300-325 m / s, and thick multilayer structures of the 4th (highest) degree of protection successfully resist shell with heat-strengthened steel core bullets weighing 9.6 g, fired from a sniper rifle with an initial speed of up to 815-840 m / s. Protective properties armored glasses are achieved due to the multilayer design and the use of special films.
Bent (curved) glass (curved glass) - sheet glass bent along the radius as a result of special heat treatment. It is given the desired shape during heating in an oven to a certain softening temperature, followed by slow cooling. The whole process of heat treatment of finished sheet glass in a special furnace to change its shape is called bending, so bent glass is also called bent glass. The minimum bending radius depends on the thickness of the glass. For glass with a thickness of 4 mm, the minimum bending radius is 80 mm, for glass with a thickness of 5 mm - 120 mm, for glass with a thickness of 6 mm - 160 mm, for glass with a thickness of 8 mm - 230 mm, for glass with a thickness of 10 mm - 350 mm, for glass 12 mm thick, the minimum bending radius is 500 mm.
Tempered glass (toughened glass) - sheet glass subjected to special chemical or heat treatment in order to increase mechanical strength to impact, resistance to temperature extremes and ensure a safe fracture pattern. During processing, the glass surface was rapidly cooled from a temperature close to the softening point, therefore, after complete cooling, residual compressive stresses remained on the surface. This increases the thermal and mechanical strength of tempered glass. In the event of destruction, it forms small, harmless fragments and does not fall out in large pieces. Belongs to the safety glass group. The allowable service bending stress for tempered glass with a safety factor of 1.0 is 175 MPa compared to 75 MPa for ordinary glass with the same safety factor. The flexural strength generally can reach 250 MPa, which is more than 5 times higher than ordinary sheet glass. An increase in mechanical strength leads to an increase in heat resistance. For tempered glass, the heat resistance reaches 1800 ° C compared to 400 ° C for ordinary sheet glass. The optical properties of glass (transmission, absorption, and reflection coefficients) remain virtually unchanged after hardening. The light transmission of transparent tempered glass is at least 84%. Finished tempered glass cannot be cut, drilled or subjected to other types of machining. The most vulnerable point of tempered glass is its edges. In the manufacture and installation of translucent structures, it is necessary to protect its ends from bumps, scratches and other influences.
Protective glass is the general name of structurally different types of glass designed to protect personnel and material assets from hazardous influences, as well as premises from penetration. It is both fire-resistant and impact-resistant (laminated) or bullet-resistant (armored) glass. Protective laminated glasses comply with GOST R 51136 and are various compositions of several silicate glasses glued together. As part of the composition, the use of organic glasses, polycarbonate, reinforcing films and other polymeric materials is allowed. The light transmission of such glasses is at least 60%. Glasses withstand temperatures up to +60 °С at a humidity of 95%, and in frost-resistant design - up to minus 40 °С.
Laminated glass or triplex is a multi-layered architectural sheet glass, consisting of two or more sheets glued to each other over the entire surface with a polymer film or a special laminating liquid. In the event of glass breakage, the inner laminating layer holds the resulting fragments. Therefore, laminated glass belongs to the safety glass group. Triplex is his the simplest option, according to the name, consisting of three layers: two glasses and a film between them. Multi-layered laminated glass helps to protect the room from the harmful effects of ultraviolet rays and street noise. Film-coated systems are more expensive than analogues made using a laminating liquid. By using various types of laminating films in combination with different amounts and thicknesses of glass components, it is possible to achieve not only tinting of the finished product in the desired color, but also its significant hardening.
Frosted glass is a final product obtained by a special etching method. Matting (transparent matt etching) is a very long and laborious process of obtaining a uniform matte or transparent pattern of various depths on the glass surface by etching. Etching is based on the properties of hydrofluoric acid vapor to form insoluble salts during interaction with the surface of the finished glass
Neutral glass is characterized by high chemical resistance.
Low-e glass (low E glass) - energy-saving glass with low emissivity (emission). The lower the emissivity of glass, the less heat exchange between the air environments separated by it and the less heat loss through a translucent structure with such glass or double-glazed windows. Low-emissivity glass transmits visible light well with a wavelength of 770-380 nm and reflects long-wave thermal radiation, also called infrared, with a wavelength from 1 mm to 770 nm. Because of this selectivity, low-e glass is also called selective. These properties are provided by applying a "hard" (K-glass) or "soft" (E-glass) coating based on metal oxide to the surface. E-glass (soft coated glass, in Russian transcription it is read as "I-glass", also referred to as Double Low-E or "i-glass") - glass with a "soft" sputtering, having a neutral coating applied by cathode sputtering in vacuum at the end of the glass production process. Delays up to 90% of thermal radiation. K-glass (hard coat glass) is an energy-saving glass with a "hard" spray coating by pyrolysis directly during glass production. Sputtering occurs on liquid glass, while atoms penetrate into its surface layer. Such a coating, unlike E-glass, cannot be removed, it is resistant to abrasive materials, which makes it possible to transport, store, cut and process K-glass as usual without losing its energy-saving properties. K-glass is somewhat worse than E-glass, as it retains about 70% of thermal radiation. Otherwise, E- and K-glasses are practically the same. They can be tempered, but a special oven is required to temper low-e glass.
Flameproof glass is glass that is indestructible when heated or in direct contact with a flame. More often such glass is called heat-resistant. As a rule, this is borosilicate glass. Fire windows manufactured using fire-resistant glass comply with the requirements of GOST 30247.0-94 and GOST 30247.1-94. The fire resistance limit is expressed in minutes and for special products is indicated, for example, E 60, E 45, E 30 or E 15. Or EI 60, EI 45, EI 30 or EI 15. The numbers indicate the time in minutes during which the structure fulfills its functions, and the letters correspond to the type of action. Limit states with respect to fire are characterized by a loss of integrity as a result of the formation of through cracks or holes that allow the penetration of combustion products or flames (marking E). As well as the loss of thermal insulation ability (marking I). This is understood as an increase in the heat flow power to the limit value of 3.5 kW at a distance of 0.5 m from the glass surface.
Polished glass - transparent sheet glass, processed by mechanical grinding and therefore also called polished. Differs in high quality of finishing of a surface. Both surfaces are ground and polished for flatness and parallelism. Such glass does not distort the shades of transmitted light, does not cause strong surface reflections and provides a clear, undistorted image when viewed through it. Polishing is necessary for glasses obtained by drawing (Furko's method). Glasses obtained by the float method, as a rule, do not need polishing.
Rolled glass - sheet glass produced from the original glass mass by rolling it continuously between two rolls or periodically rolling on a table using one roll.
Reflective glass - glass with a metallized reflective coating applied to one of its sides.
Solar control glass - as a rule, tinted or reflective glasses that reduce the transmission of solar radiation in the entire spectrum of wavelengths or in part of it. Sunglasses can be body-dyed glasses in bronze, brown, gray or green, as well as glasses with some coatings. According to the principle of operation, all sun protection glasses can be divided into two types: predominantly reflecting radiation and predominantly absorbing it. Glasses of the first type are characterized by a surface with a thin metal layer preventing the penetration of radiation. Some glasses of the second type are characterized by their heating, which occurs in the process of absorbing solar radiation. In this case, part of the heat is inevitably transferred to the interior of the room. Colorless glasses with thin metal oxide, ceramic or polymer coatings that are transparent to visible rays are able to absorb part of the infrared (thermal) radiation of the sun, and therefore they heat up much less. Their lighting characteristics weakly depend on the thickness of the sheet. At the same time, not all types of sun protection glasses protect from direct sunlight - the brightness of the solar disk in some cases remains too high.
Heat-absorbing glass - protective sheet glass designed to reduce the penetration of thermal radiation. In terms of intended purpose, heat-absorbing glass is very close to the sun-protection glasses just described, but differs from them in reduced light transmission not so much of the visible part of the spectrum as of infrared rays. It has a blue color with a bronze or gray tint, light transmission does not exceed 70%. Other characteristics are comparable with flat sheet glass produced in accordance with GOST 111-2001. Heat-absorbing glass is made according to TU 21-23-23-81 from colored glass mass by vertical thermal molding.
Tinted glass, also often referred to as mass-tinted glass, is tinted glass with reduced light transmission. The desired color is imparted by introducing dyes during the glassmaking process. In addition, glass can be tinted by applying special coatings (tinted films or sprayed thin metal layers), but in this case it is called tinted rather than bulk-tinted glass.
Figured rolled glass - sheet colorless, colored or translucent rolled glass, having on one or both sides decorative processing the entire surface in the form of a relief regularly repeating pattern. Such glass comes in different colors, patterns, and thicknesses, and can also have different light transmission. Patterned glass is produced in full compliance with GOST 5533-79 in the form of sheets with a length of 600 to 1600 mm for glasses with a thickness of 3, 4, 5 and 6 mm, and, in addition, for glasses with a thickness of 3 and 4 mm in the form of sheets with a width of 400 up to 1200 mm. For glasses with a thickness of 5 and 6 mm, it is possible to produce sheets with a length of 600 to 2200 mm and a width of 400 to 1600 mm. The chemical compositions of rolled, patterned and reinforced glass differ little from each other. The physicochemical properties of patterned and reinforced glass are the same as those of sheet window glass, while the light transmission of patterned glass is reduced. The coefficient of total light transmission of glass having a pattern on one surface is 0.75, and on both surfaces it is 0.65, since patterned glass must transmit and scatter light.
Facet (facet cutting, beveling) is a special processing of the glass edge, which allows you to artistically change the surface of the entire product by streams of light refracted in the created edges. Figured facet is called a particularly complex processing with high precision of the execution of curved surfaces.
Float glass (float glass) - sheet glass obtained by molding a glass melt on a metal melt at a controlled temperature in a protective atmosphere. Also called thermopolished glass. The most common type of glass obtained by the float method, in which the glass, when leaving the melting furnace, is poured onto the surface of molten tin and then passes through the cooling zone for further processing. Float glass is characterized by exceptional evenness and the absence of optical defects. It does not require subsequent grinding, unlike glass produced by drawing. In 1959, Alistair Pilkington, the founder of the subsequently world-famous English company "Pilkington", developed a fundamentally new method for producing polished glass by forming a glass ribbon on molten tin, called the float process ("floating glass"). New method turned out to be so promising, cost-effective, technically advanced that in just 10-15 years it completely replaced mechanical conveyors for glass processing and became dominant in the world. For the first time, such a method of forming glass on a melt was proposed long before the development of Pilkington. In 1902, American inventors W. Hill and A. Hitchcock (independently of each other) patented a method and device for producing sheet glass from a metal melt. According to their developments, suitable metal tin or its alloys with copper could be used to form a glass ribbon. However, the absence at that time of technical devices for the implementation of this process, the insufficient knowledge of the physicochemical phenomena occurring during the formation of a glass ribbon, did not allow the proposed method to be put into practice. It is noteworthy that in the same 1902, simultaneously with the above-mentioned Hill and Hitchcock, Fourko proposed his method of industrial glass production by drawing.
Fourko method - developed in 1902 by Emil Fourko, a method for the industrial production of sheet glass by pulling vertically in the form of a continuous tape from a glass furnace through rolling rollers. After passing through the cooling shaft, the glass was cut into sheets, followed by grinding and polishing. The thickness of the finished glass was controlled by changing the drawing speed, and the glass itself was also called drawn glass. The method was widely used to obtain glasses until the appearance in 1959 of the above-described float process, the widespread introduction of which was supplanted.
Fusing is a glass sintering technology in which a pattern composed of several separate multi-colored glasses is baked in a special oven at a temperature of 800 ° C into a single integral product. Since before sintering all the details of the future product are laid out on the base glass, fusing does not require the use of metal profile like the stained glass technique.
Pure glass (clear glass) - transparent colorless glass. Super clear glass (extra-clear glass) - transparent colorless glass with a reduced iron content, due to which its increased transparency is achieved.
Electrochromic glass is a lighting installation, which is a double-glazed window, structurally consisting of two glasses connected by a special film. The film is a polymer composition with small inclusions of liquid crystals. The entire installation operates at a voltage of 9-12 V and is connected to a conventional (household) power supply with a voltage of 220 V. In the off state, the glass is opaque matte or milky white, because the liquid crystals are arranged randomly and scatter the light falling on them in all directions. Under the influence of an electric current, the crystals are aligned and the light passes unhindered through the glass. Light transmission in working condition is about 85%, which is comparable to ordinary glasses. The transition from working to non-working and back is very fast. The installation must not be subjected to insolation (irradiation with direct sunlight), as the crystals disintegrate under the influence of direct sunlight.
Glass "Metelitsa" - decorative glass of domestic production with a wave-like non-repeating pattern with matte protruding areas. The pattern creates a partial scattering of light and limits see-through through the glass. "Metelitsa" can be produced with a mirror aluminum coating according to TU 21-23-70-82. It is produced in the form of sheets with maximum dimensions of 1500x1300 mm. Depending on the type of pattern, the thickness of the glass ranges from 3 to 8 mm.
Glass "Moroz" - decorative patterned glass of domestic production. The name of the glass was given by a non-repeating pattern on one of its surfaces, reminiscent of hoarfrost. Thanks to this pattern, Frost glass scatters light and excludes through visibility. It is produced according to OST 21-24-85 colorless or painted with a thickness of 3 to 6 mm, with a maximum sheet size of 1800x1000 mm.
"Soft" self-cleaning glass is a special glass, introduced for the first time in the world in 2002 by the English company Pilkington. The unique properties of Pilkington Activ glass are obtained by magnetron sputtering of a thin transparent coating of titanium oxide. Under influence ultraviolet radiation this material provokes a chemical reaction that decomposes organic compounds on the surface of the glass. When it rains, all the dirt is washed away. Thus, this type of glass does not need to be cleaned with special means.
Today for making quality windows different types of glass are used. This allows manufacturers to be more flexible in order fulfillment and responsive to consumer needs. Thanks to this approach, companies have the opportunity not only to produce exactly the product that the client needs, but also not to overcharge for it. The range of glasses available to manufacturers allows them to solve diverse tasks - to increase the energy efficiency of windows, to delay and reflect light waves of different spectra, to ensure safety and aesthetic appeal.
What is the difference between different types of glass
The basis of all glasses is a silicate mass, which acquires a high light transmission capacity during the production cycle. You can read more about this in interesting articles and on OknaTrade. That is, with a few exceptions, initially ordinary glasses have approximately the same characteristics, but various individual features are provided through the use in their manufacture:- special mineral additives;
- metallized low-emission coatings;
- polymer films;
- steel mesh.
This type of glass, the most common today, is sheets with a thickness of 0.4 to 25 mm, which are formed on the melt of tin. This technology makes it possible to provide glass with a smooth surface and reduce its cost, since manufacturers no longer need to polish and grind the surface of the sheets. Float glass can be either transparent or bulk tinted. In the second case, special mineral additives are added to the silicate mass, which give the sheets a blue, green, red or bronze color. Both types are actively used for the manufacture of double-glazed windows, but the most common is transparent glass float glass with a thickness of 4 mm.
You can improve the performance of float glass by gluing windows with polymer films, which help to increase the level of heat and sound insulation.
Energy efficient glass
For the manufacture of warm windows today, glass with a special selective coating is increasingly used. The metallized layer deposited on the surface transmits visible rays sunlight and traps heat. Thanks to this division, it was possible to provide windows with high energy efficiency without any reduction. Currently available:- i-glass - have a soft coating;
- k-glass - have a hard coating.
A detailed comparison of the characteristics of these two modifications is given in a special article on WindowTrade. Energy-efficient glass not only allows you to better keep warm in winter, but also keep cool in summer - that is, they fully function in 2 directions.
Energy-efficient double-glazed windows have approximately the same coefficient of heat transfer resistance as conventional double-glazed models. An additional benefit from their use is that they can significantly reduce the weight of windows and do not allow interior rooms to warm up quickly in summer.
Triplex glass
Because conventional float glass breaks easily even with a slight impact, the window industry needed a material that was impact-resistant with good light transmission and a high level of security. So the triplex was born. It was obtained by combining ordinary glass and a polymer film, which is located between two sheets. This combination made it possible to simultaneously increase both strength and safety. Even if triplex glass can be broken, thanks to the film, the fragments will not scatter throughout the room. At the same time, the number of layers in a triplex can be more than three, which makes it possible to further increase the impact resistance of products. Today, technologies make it possible to produce triplex with four layers of polymer film, the total thickness of which is 32 mm.
Reinforced glass
To strengthen the glass, a metal mesh can be used, which, during the casting of sheets, fits into the body of the silicate mass. In production, 3 types of steel wire can be used:- chrome plated;
- nickel-plated;
- annealed.
If normal float glass is heat treated at 650-680°C and both sides are cooled quickly, it will become tempered. This means that such sheets will be much more difficult to break. It also increases thermal resistance and increases safety - tempered glass fragments have blunt edges, making it almost impossible to get hurt. Such products are most vulnerable to end impacts, and this should be taken into account when designing glass structures.
Self-cleaning glasses
For those installed in hard-to-reach places Windows that are difficult to clean from the outside are increasingly using an innovative product - self-cleaning glass. These products have a special coating, due to which, under the influence of sunlight, they independently decompose organic dirt on their surface. The substances remaining after the chemical reaction are washed off with rainwater, which flows evenly over the entire area of the double-glazed window and leaves no marks or streaks.Reflective glass with reflective coating
These glasses are somewhat similar to energy efficient ones, but are designed for other purposes - reflection or segregation of sunlight. The protective metallized coating can also be soft or hard and differ in the degree of resistance to external influences. Some types of reflective glass are able to protect against overheating while maintaining the high light transmission of windows.Sun reflective glass has a mirrored surface, so it can be used to provide privacy in some cases.
Tinted glass
Tinting allows you to darken the premises, protect them from overheating and, in some cases, reduce heat loss. This type of glass is represented by 4 modifications:- tinted in mass;
- with pyrolysis coating:
- pasted over;
- coated with metal oxides deposited in a vacuum chamber.
The characteristics of these products and the way we care for us depend on the type of tinting. Glass tinted in bulk is considered the most resistant to mechanical damage, but they themselves quickly heat up in the sun and begin to transfer heat to the interior. As a result, it is recommended to give preference to glass with pyrolysis or vacuum coating.
GLASS
Any material that, when cooled, passes from a liquid to a solid state without crystallization, is properly called glass, regardless of its chemical composition. This definition includes both organic and inorganic materials. However, commonly used glasses are almost always made from inorganic oxides.
PROPERTIES
The widespread use of glass is due to the unique and peculiar combination of physical and chemical properties that is not characteristic of any other material. For example, without glass, conventional electric lighting as we know it would probably not exist. No other bulb material was found electric lamp, which would combine such important qualities as transparency, heat resistance, mechanical strength, good weldability with metals and low cost. Likewise, the precision optical elements of microscopes, telescopes, cameras, film and video cameras, and rangefinders would probably have nothing to make of in the absence of glass. All of the above properties are ultimately due to the fact that glasses are amorphous and not crystalline materials. At room temperature, glass is a hard brittle material and usually remains so when the temperature rises up to 400 ° C. However, as the glass is further heated, the glass gradually softens, almost imperceptibly at first, until finally it becomes a viscous liquid. The process of transition of glass from a solid to a liquid state is not characterized by any definite melting temperature. With proper cooling liquid glass this process occurs in the opposite direction also without crystallization (deamorphization).
GLASS PRODUCTION
raw materials. The mixture, or charge, from which glass is prepared contains some main materials: silica (sand) is almost always; soda (sodium oxide) and lime (calcium oxide) usually; often potash, lead oxide, boric anhydride and other compounds. The blend also contains glass fragments from a previous meltdown and, as the case may be, oxidizers, decolourants, and dyes or opacifiers. After these materials are thoroughly mixed with each other in the required ratios, melted at a high temperature, and the melt is cooled quickly enough to prevent the formation of a crystalline substance, the target material, glass, is obtained. Although sand does not look like glass in appearance, most common glasses contain from 60 to 80 wt.% sand, and this material, as it were, forms a skeleton, relative to which the glass formation process proceeds. Glass forming sand is quartz, the most common form of silica. It is like sand from a sea beach, however, most of the foreign matter has been removed. Sodium oxide Na2O is usually introduced into the batch in the form of soda ash (sodium carbonate), but sodium bicarbonate or sodium nitrate is sometimes used. All these sodium compounds decompose to Na2O at high temperatures Oh. Potassium is used in the form of carbonate or nitrate. Lime is added in the form of calcium carbonate (limestone, calcite, precipitated lime) or sometimes in the form of quicklime (CaO) or hydrated (Ca(OH)2) lime. The main sources of boron monoxide for glass production are borax and boric anhydride. Lead oxide is usually introduced into the charge in the form of red lead or lead litharge.
Glass types. Quartz glass. Glass consisting of silica alone is properly called fused quartz or quartz glass. This is the simplest glass in terms of its chemical and physical properties, and it has many necessary parameters: it does not deform at temperatures up to 1000 ° C; its coefficient of thermal expansion is very low, and therefore it is resistant to thermal shock when the temperature changes abruptly; its volumetric and surface specific electrical resistances are very high; It perfectly transmits both visible and ultraviolet radiation. Unfortunately, quartz glass is very difficult to melt and process into products. High price Quartz glass limits its use to special-purpose items such as laboratory glassware, mercury lamps, and high-temperature optical components.
Soda silicate glasses. Soda silicate glasses are obtained by fusing silica (silicon oxide) and soda (sodium oxide). A mixture of 1 part sodium oxide (Na2O) with 3 parts silicon oxide (SiO2) melts at a temperature 900°C lower than pure silica; sodium oxide acts as a strong flux. Unfortunately, such glasses dissolve in water, and although they are extremely important for industrial applications, most products cannot be made from them.
Lime glass. Ancient glassmakers discovered that the water solubility of soda silicate glasses could be eliminated by the addition of lime. Analysis of ancient glasses shows a striking similarity of their chemical composition with that of modern glasses, although modern glassmakers, unlike the ancients, also know that the addition of small amounts of other oxides, such as magnesium oxide MgO, aluminum oxide Al2O3, barium oxide BaO, further improves the quality of the glass. . If the main ingredients of the mixture are oxides of Na2O, CaO and SiO2, then the glasses obtained are called soda-lime-silicate, soda-lime or simply lime glasses, regardless of the presence of other components. With slight changes in the composition, these glasses are widely used for the manufacture of sheet and mirror glass, glass containers, bulbs for electric lamps and many other products. These glasses are relatively easy to melt and process into products, and the raw materials are inexpensive. Probably 90% of the glass produced today is lime.
Lead glass. Lead glasses are made by fusing lead oxide PbO with silica, a sodium or potassium compound (soda or potash), and small additions of other oxides. These soda-lead (or potassium)-silicate glasses are more expensive than lime glasses, but they melt more easily and are easier to manufacture. This allows the use of high concentrations of PbO and low concentrations of alkali metal without sacrificing fusibility. This composition raises the dielectric properties of the material to such a level that it makes it one of the best insulators for use in radios and television tubes, as insulating elements of electric lamps and capacitors. The high content of PbO gives high values refractive index and dispersion, two parameters that are very important in some optical applications. These same characteristics give lead glass the brilliance and brilliance that adorns the finest tableware and works of art. Most glass called crystal is lead glass.
Borosilicate glasses. Glasses with a high content of SiO2, a low content of alkali metal and a significant content of boron oxide B2O3 are called borosilicate. Boric anhydride acts as a flux for the silica so that the alkali metal content of the charge can be drastically reduced without excessively raising the melt temperature. In 1915, Corning Glass Works began producing the first borosilicate glass under the trade name Pyrex. Depending on the specific composition, the resistance to thermal shock of such glasses is 2-5 times higher than that of lime or lead; they are generally far superior to other glasses in chemical resistance and have properties useful for electrical applications. This combination of properties made possible the production of new glass products, including industrial pipes, centrifugal pump impellers, and household cookware. The mirror of the largest telescope in the world at Palomar in California is made of Pyrex glass.
Other glasses. There are many other types of glass for special purposes. Among them are aluminosilicate, phosphate and borate glasses. Glasses are also produced in a variety of colors for the manufacture of lenses, light filters, lighting equipment, cosmetic containers and household utensils.
Cooking. Glass is brewed by holding a mixture of raw materials at high temperatures (from 1200 to 1600 ° C) for a long time - from 12 to 96 hours. This mode ensures the necessary chemical reactions occur, as a result of which the raw mixture acquires the properties of glass.
In ancient times, brewing was carried out in clay pots with a depth and diameter of 5-7 cm. Currently, fireclay pots of much larger sizes are used, containing from 200 to 1400 kg of charge, for the production of optical, artistic and other types of glass special composition. In one oven, 6 to 20 pots can be aged. Large masses of glass are boiled in continuous bath furnaces. A constant level of molten glass in the bath is maintained by continuously supplying the mixture at one end of the installation and extracting the finished product at the same speed from the other end; in this mode, some glass melting furnaces operated for five years before the need for repairs arose. Large kilns, sometimes holding several hundred tons of molten glass, accommodate intensive mechanical production. Both pot and tank stoves are usually heated by burning natural gas or oil.
Processing into products. When it comes to processing into products, glass differs from most other materials in two ways. First, it must be processed, being extremely hot and semi-liquid. Secondly, the shaping operations must be carried out over short periods, lasting from a few seconds to at most a few minutes, during which time the glass is cooled to a solid state. If further processing is required, the glass must be heated again. In the molten state, glass can be drawn into long filaments that are flexible at high temperatures, removed from the total mass by a tool immersed in it in the form of a small bunch, picked up by the end of a glass blowing tube, or poured into molds to obtain castings or pressings. Since glass fuses easily with metal, the individual parts of a complex product are joined to each other after reheating, which also ensures the cleanliness of the joined surfaces. The rotation of the workpiece at a constant speed during processing gives the product an axisymmetric shape. Finished glass products are subjected to an annealing process with a slow cooling step for stress relaxation. For all the time of glass production, four main methods of its processing have been created: blowing, pressing, rolling and casting. The first three methods are used in both small-scale manual and continuous machine production. Casting, however, is difficult to adapt to high-volume production.
Latest Achievements. In the development of mechanization tools for the rapid and cheap production of glass products in the 20th century. more successes have been achieved than in the entire previous history of glassmaking. In the 1900s, although the foundations for the mechanization of technological processes and mass production, glass was still used mainly for making only five kinds of products: bottles, tableware, windows, lenses and jewelry. Since then, glass has been produced by many enterprises and has found application in literally thousands of different areas. Now glass is easily adapted to customer requirements. It can be transparent, translucent or opaque, colored or colorless. Some types of glass are as light as aluminum, while others are as heavy as cast iron; There are glasses that are stronger than steel. They are used to make fibers 10 times thinner than a human hair and sheets as thin as paper. Glass objects can be tiny, fragile and light, or as massive as the solid 508 cm, 20 ton mirror of the Palomar Telescope.
Flat glass. During and immediately after the First World War, new and completely continuous methods were developed for the manufacture of both window and plate glass. In 1928 laminated safety glass for automobiles was created. Shortly thereafter, the production of tempered flat glass was mastered by heat treatment (quenching with high tempering) of hard polished sheets. This process increases the strength several times and gives a product with exceptionally high flexibility and resistance to abrasion and all kinds of mechanical and thermal shock. When such glass breaks, it does not break into long, sharp shards like ordinary glass, but into small, rounded pieces that are relatively harmless. Tempering is effective in strengthening not only flat glass, but also cookware, measuring glass, goggle lenses, and round lamp bulbs. Double-glazed windows, replacing inset window sashes, are a relatively new development in flat glass design. They consist of two or more sheets of glass hermetically connected around the perimeter by a frame. The space between the sheets is filled with purified and dried air. Compared to single glazing, double-glazed windows reduce heat loss by almost 50% and permanently eliminate the problems associated with the use of external window sash, dust penetration and moisture condensation.
Wall glass blocks. The production of wall glass blocks and fiberglass began in 1931. It is hard to imagine two other types of glass products that are so different from each other. Wall glass blocks are massive and are made by welding two pressed semi-blocks with the formation of a hermetic cavity between them. Such elements are mounted during construction using conventional tools and materials. The "walls of daylight" obtained from them transmit most of the solar radiation falling on them, but reduce its brightness, provide good thermal insulation and practically exclude moisture condensation. These useful properties have led to the widespread use of wall glass blocks as elements of building structures.
Fiberglass. Unlike household glass, fiberglass is usually made in the form of filaments with a diameter of less than 1 micron. Since each fiber is essentially a solid glass rod, in bulk it has all the properties of glass. Fiberglass is heat-resistant and non-flammable. It does not absorb moisture, does not rot and is not subject to chemical decomposition. It is weather, acid, oil and corrosion resistant and does not conduct electricity. Fiberglass can be used to make threads, tapes, braids and cords. From somewhat thicker, short fibers, an elastic, cotton-like mass is obtained, called glass wool. In this form, fiberglass is an excellent thermal insulator. Various types of fiberglass in combination with asbestos, mica, plastics and silicones give excellent composite materials. Indeed, materials consisting of parallel glass filaments embedded in a polyester or other matrix can be much stronger per unit mass than conventional ones. construction materials including steel, aluminium, magnesium and titanium. Glass fiber reinforced plastics of this type are now widely used for aircraft and missile parts, pipes, tanks, boat hulls and building panels. The glass fiber industry has grown at an astonishing rate due to the widespread use of this type of glass in composite materials.
Special quartz glass. In 1939, another wonderful type of glass was invented, called 96% quartz glass. This product is almost equivalent in properties to pure fused quartz, but can be produced cheaper and in a wide variety of shapes and sizes. The resistance to thermal shock of this type of glass is so great that, after being heated to the point of softening, it can be immediately immersed in cold water without causing breakage. The specific electrical resistance and chemical resistance of this type of glass are also very high. Some varieties of 96% quartz glass have exceptionally high transmittance in the mid-ultraviolet region of the spectrum, which allows such glass to be used in solar and germicidal lamps, laboratory equipment and special electrical products.
Foam glass. Foam glass, another product of glassmakers' ingenuity, is similar in texture to bread and can be cut into pieces of the desired size. Designed in 1940, this glass weighs so little that it does not sink in water, yet is tough, non-flammable and odorless. Such an anomaly of properties is created after mixing finely divided coke and glass and heating the mixture to a high temperature. The powdery mixture melts into a black foam that fills the volume of the mold and then solidifies. The result is a solid cellular material with hundreds of thousands of air-filled isolated cells per 1 dm3. After removing the molds, the foam glass blocks are cut to the right sizes. This wonderful product weighs about the same as cork and was used as a substitute for cork during World War II, as well as cork, foam rubber and kapok. Like cork, foam glass is an excellent insulator. However, unlike cork, it is not affected by moisture and moisture condensation, so it is very suitable for lining cold rooms and domestic refrigerators. Foam glass can be equally successfully used for high-temperature thermal insulation up to 425 ° C, since it not only does not burn, but also drowns out the fire. New variety Foam glass contains 99% silica and can be used at temperatures up to 1200°C.
Metallization. A thin layer of metal can be deposited on the glass surface; in this case, the connection is so strong that rather massive metal parts can be soldered to the metal coating. This method is widely used in the radio and electrical industries.
conductive coatings. A number of unusual applications of glass have been discovered in connection with the fact that it can be given the property of surface conductivity. This is achieved by sputtering a thin, transparent, almost invisible layer of metal oxide onto the glass surface. Such a coating is very durable and has a surface resistance ranging from 10 to 100 ohm/cm2. Lime glass can be used at normal temperatures, while borosilicate glass can be used at high temperatures. Radiant heating panels made of such glass can operate at temperatures up to 350 ° C. Such panels are a good source of energy for long-wave infrared radiation, which most substances and media absorb with an efficiency of 90% or more. In this way table-top glass radiators and auxiliary heaters for rooms are made. Conductive coatings applied to aircraft windshields keep them warm and ice-free.
Electrical products. Glass bulbs are widely used as shells for incandescent lamps and cathode ray tubes. Wirewound resistors, transformers, capacitors, relays, and switches can be sheathed in tempered glass with leads through glass insulators. Large bushings weighing up to 22 kg, designed for high currents and high voltages, are made by centrifugal casting of glass around metal bushings. With the use of glass, capacitors are made of both constant and variable capacitance. Fixed capacitors use sheet glass up to 0.025 mm thick. The variable capacitor consists of a glass tube manufactured to close tolerance, part outer surface which is metallized to form one plate. A rod made of brass or Invar is inserted inside the tube, forming the second lining. Glass tubes or rods coated with a carbon, metal or metal oxide film are used as resistors.
Photosensitive glasses. In 1947, it was discovered that glasses of certain compositions, when exposed to ultraviolet radiation, form a latent image, which can be developed by heating the glass just above the annealing temperature. For example, you can put a photographic negative on glass and irradiate it with ultraviolet light, and then heat the glass; as a result, the image reproduced in color will appear in the glass volume. The color of the image depends on the type of photosensitive metal introduced into the mixture. One of the compositions produces an opal glass of such a nature that dilute hydrofluoric acid etchs the irradiated part fifteen times faster than the unirradiated part. This huge difference in solubilities allows chemical etching to take place. Holes less than half the average diameter of a human hair can be etched in glass in this way, up to 100,000 holes per 1 cm2. Glasses of this type are used for the manufacture of light panels, name plates and decorative tiles, as well as as sensitive elements of dosimeters. After exposure to penetrating radiation, some of these glasses glow brightly when irradiated with ultraviolet light, while others change their color. The intensity of the fluorescence, or the degree of color change, is proportional to the radiation dose received.
Glass ceramics. This hybrid name refers to materials that were first produced as glasses, and then in their entirety transferred to a crystalline state. They are manufactured by Corning Glass Works under the registered trade names Pyroceramics and Photoceramics. Raw materials for the manufacture of glass ceramics are approximately the same as for the manufacture of glass, however, they include some additional additives that play the role of nucleating agents. After molding one of conventional ways- pressing, blowing or rolling - the product is heated to the temperature of the formation of crystallization nuclei. In 1 cm3 of the product, billions of such nuclei are formed, which grow to the smallest crystals, although no visible crystallization occurs. Then the temperature rises, and crystallization around the seed crystals begins in the entire volume of the glassy product. The process continues until the growing crystals collide with each other and the entire mass of the product becomes crystalline except for small areas of the glassy matrix at the crystal boundaries. Processing, nucleation and crystallization temperatures depend on the composition of the glass. In some cases, the formation of crystallization nuclei is carried out by exposure to X-ray or ultraviolet radiation, followed by heat treatment. Unlike ordinary ceramics, glass ceramics do not have pores, and their crystals are smaller and more uniform. Compared to base glass, glass-ceramics are harder, do not deform up to higher temperatures, and are several times stronger. One of its earliest uses was in rocket fairings. Now glass-ceramic dishes are widely used, which can be moved from the refrigerator directly to the stove. Laboratory glassware, engine cylinders, and even ball bearings are made from glass-ceramic. These developments are a major achievement in glass technology.
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